P0325 Code in 2026: Knock Sensor Wiring, Software, and the Hyundai-Kia Code It Is Not

P0325 is a code about a wire and a signal, not about knocking.

A knock sensor is a small vibration microphone bolted to the engine block. It listens for detonation — fuel igniting too early — and the engine computer uses what it hears to pull ignition timing back before the pistons are damaged. P0325 — "Knock Sensor 1 Circuit," printed by some makers as "Knock/Combustion Vibration Sensor 1 Circuit" — means the computer has lost a believable signal from sensor 1: bank 1 on a V engine, the only sensor on many four-cylinders. It says the circuit is wrong. It does not say the sensor is. P0330 is the same code for sensor 2; P0326 to P0334 are its range and high-low variants, and P0324 is the knock control system itself.

We found 527 manufacturer documents and recall filings — 379 from our search of NHTSA's index and the six knock sensor recalls, and 148 that a second, independent search found, mostly Hyundai P1326 procedures and Kia owner letters — that deal with the knock sensor, its codes or the Hyundai and Kia software built on it — service bulletins, special service messages, preliminary information, engineering cases, campaigns, recall reports and owner letters from GM, Ford, Stellantis, Hyundai, Kia, Audi, Volkswagen, Bentley, Subaru, MINI, Mercedes-Benz, Maserati, Volvo and others — and read all 527 in full, comparing near-identical letters sentence by sentence against a copy read in full; 511 turned out to be relevant. 18 name P0325 in their own text, and not one of the 18 fixes it with a new sensor: the fixes are a chafed harness, a terminal pushed out of the computer connector, wires swapped at the computer, and software. Across the whole knock-code family, the documents put wiring, connectors, mounting, moisture and software ahead of the part.

The federal complaint file tells a different story, and it starts with two makers. PulsCar went through all 1,554 complaints in NHTSA's file from 2015 to September 2026 that mention a knock sensor in the spellings we searched, name a knock sensor code or name P1326, each sorted twice, independently, by the same written rules. 1,407 concern a Hyundai or a Kia, and 1,107 of those are about the Knock Sensor Detection System — the software that turns the knock sensor into a bearing-failure alarm with its own code, P1326. Only 53 complaints name a P0324-to-P0334 code, and 11 name P0325. Outside the Hyundai-Kia software story, in 160 a knock sensor or its harness was replaced and the problem came back or turned out to be something else.

By the end you will know which of five routes your knock code is on, what each costs in 2026, whether you are looking at P0325 or at the Hyundai-Kia bearing warning, and which bulletin, recall or coverage applies to your VIN.

Claims marked 🟢 rest on a document listed in the Sources section, read in full. Claims marked ⚪ are shop-price estimates carried from our repair guides. Owner-reported figures are what people told NHTSA, published with ODI numbers, and every complaint count here comes from the 1,554 complaints sorted twice and published.

I built PulsCar after a $380 "full diagnostic" in Phuket in 2025 led to roughly $6,000 over six months across several shops (the story is on the About page). P0325 is that pattern with a twist: a cheap sensor that is easy to replace and often not the fault — and, on two brands, a code that sounds the same and means an engine. Every claim below that rests on a document names it.

What P0325 says: the knock sensor's circuit, not a knock

What the sensor does. A piezoelectric element inside the sensor produces a small voltage when the block vibrates. The engine computer watches that signal at the moments detonation would happen and retards the timing on the cylinder that knocks. On many engines the computer also uses the sensor to run the most aggressive timing the fuel allows.

What the computer checks. Whether the signal is within the expected range, whether it moves with engine speed and load, and whether the circuit is open or shorted. P0325 is the general circuit code for sensor 1; P0327 and P0328 say the signal is low or high; P0326 says it is out of range or performance. The same four exist for sensor 2 as P0330 to P0333.

What P0325 is not. It is not a record that the engine knocked, and it is not a diagnosis of the sensor. A sensor that correctly hears a real mechanical noise can set P0324 or pull timing hard; a healthy sensor with a broken wire sets P0325. And on Hyundai and Kia engines, the knock sensor's other job — listening for bearing wear — sets P1326, a different code with a different meaning.

What happens when it sets. Without a trusted knock signal, most engine computers fall back to safe, retarded timing. Owners feel it as sluggish acceleration, lower fuel economy and sometimes a rattle under load. That is the car protecting itself — but the knock protection is what is missing, so use the recommended fuel and go easy until it is fixed.

First: is it P0325, or is it the Hyundai-Kia bearing warning?

This is the question that decides the bill. Owners call both "the knock sensor." The documents do not.

Why the confusion matters. Kia's own repair bulletins label P1326 "Knock Signal Range/Performance" in some revisions, which sounds like an ordinary sensor code. The same bulletins treat it as a bearing warning. In the complaint file, 1,107 complaints are about this system, and many call it "the knock sensor recall," "the knock sensor update" or "the knock sensor went off." A reader that shows a knock code on a 2010-2021 Hyundai or Kia should be read again at a dealer or with a tool that shows maker codes, before anyone quotes a sensor.

The knock-code family, and how often owners name each

The codes are rare; the words are not. 53 of the 1,554 complaints name a code from P0324 to P0334, and 477 name P1326. Most owners wrote "knock sensor" and nothing else — which is why the complaint set was built from the words as well as the codes.

P0324 is a different animal. In two GM documents it can be set when the sensor correctly hears something mechanical (Route 3).

The maker atlas: who wrote about knock codes, and what they blamed

The routes below quote each document; this is the map.

GM: wiring, mounting, and software. 🟢 19-NA-032 traces P0325 and P0330 on 2018 Malibu 1.5 models to software; on early VINs the fix also swaps the two knock sensor wires at the engine computer. 🟢 22-NA-229 traces a possible audible knock on 2023 Escalade 6.2 models to software that failed to detect knock sensor circuit failures, and says not to replace parts. 🟢 Emission recall 12292 reconnects reversed knock sensor wires on 2013 Malibu 2.5 models. 🟢 PIP5836A, PIP5273, PIP5773B, PIP5985, PIP5576 and 20-NA-207 send technicians on trucks, SUVs, Colorados and Camaros to casting flash, loose connectors, a park-neutral circuit and connector seating — two of them say the cause is still unknown.

Ford: the harness and a shared coolant sensor. 🟢 18-2367 traces P0325 on 2016-2017 Explorers and Police Interceptor Utilities with the 3.5 EcoBoost, built on or before 30 September 2016, to a possible wire chafe near connector C109. 🟢 Special service messages 46906, 47791, 48991, 49004 and 49407 tie P0330 on 2.7 and 3.0 EcoBoosts to a coolant temperature sensor that shares the knock sensor harness.

Stellantis: software, and two cases that need no parts. 🟢 Flash bulletins name P0325 on 2022 Ram ProMaster 3.6 vans and on 3.0 Hurricane Ram 1500s, Wagoneers and Grand Wagoneers. 🟢 Two engineering cases fix P0325 and P0330 by rerouting a chafed or pinched harness — "no parts required." 🟢 On 2017 1.4-liter Fiats and Renegades, the scan tool showed P0000 instead of P0326.

Audi, Volkswagen, MINI, Maserati and Subaru: sensitivity and moisture. 🟢 Audi says "OBD diagnostics are too sensitive"; 🟢 a 2026 Audi bulletin blames moisture absorbed during long standing; 🟢 Volkswagen and MINI say not to replace parts before software — MINI's fault 168A20, "Knock control; system error," is fixed by programming the engine computer; 🟢 Maserati burns moisture off before any sensor; 🟢 Subaru changed the sensor design for heat.

Hyundai and Kia: the bearing warning. 🟢 Dozens of campaign bulletins and recalls install the Knock Sensor Detection System, and a second family of bulletins tells dealers what to do when it sets P1326. 🟢 Three Kia bulletins cure P0326 and P0328 with software alone. 🟢 Hyundai and Kia procedures for P1326 include a wiring interference check and, after a passed bearing test, a new knock sensor. 🟢 A 2024 Hyundai bulletin traces P1326 on N models to water in the knock sensor connector.

The 10-minute knock-code check

1. Read the code with a tool that shows maker codes (2 minutes). P0325 and P1326 lead to different places. Write down every code and the freeze frame.

2. Watch the light (1 minute). Steady, or blinking continuously? Blinking with limp mode on a Hyundai or Kia is Route 5.

3. Listen (2 minutes). A deep knock that rises with engine speed, even in neutral, is inside the engine — stop driving. A light rattle only under load on cheap fuel is detonation, which is what the sensor is supposed to hear.

4. Check the oil (2 minutes). Level and date of the last change. On Hyundai and Kia engines the oil history decides coverage; on any engine, low oil can be the story behind a knock.

5. Think back and run the VIN (3 minutes). Recent work near the intake, rodents in the engine bay, a car wash or heavy rain, a software update? Then check nhtsa.gov/recalls and ask a dealer about campaigns, which do not always show as safety recalls.

Seven knock-code situations, and which is yours

"A knock code on a Ram, Wagoneer, 2018 Malibu 1.5, 2023 Escalade, Audi or Volkswagen with a bulletin." Software. → Route 1.

"P0325 after engine or intake work, or with chewed wires, or on an early 2016-2017 Explorer 3.5 EcoBoost." Wiring and connectors. → Route 2.

"A knock code after rain, a car wash or long storage, or a code with no noise at low mileage." Moisture or mounting. → Route 3.

"P0325 with an open or shorted sensor confirmed, wiring good." The sensor. → Route 4.

"A Hyundai or Kia with a blinking light, limp mode and a 'knock sensor' warning." The bearing warning, P1326. → Route 5.

"P0325 on any other car, steady light, no bulletin found." Wiring first, then a sensor test. → Routes 2 and 4.

"A deep knock that follows the revs." Not a sensor problem at all. Stop driving and have the engine inspected.

The knock-code price ladder, from the bottom up

The first three lines decide whether any of the rest is needed. The ⚪ figures come from our engine knocking guide and our guide to the most expensive check engine codes; the owner figures are listed with ODI numbers in the published file.

What does it cost to fix P0325 in 2026, and when is a new knock sensor the wrong purchase? Our repair guides carry a knock sensor replacement at $200 to $500, more where the sensor sits under the intake manifold. In PulsCar's reading of 1,554 federal complaints, owners report $140 to $995 for a knock sensor on Hyundai and Kia models, $900 to $2,900 when rodents chewed the wiring, and $3,200 to $20,000, median $8,000 and mostly quotes, for a Hyundai or Kia engine. A new sensor is the wrong purchase when a bulletin names software for your vehicle, as GM's does for 2018 Malibu 1.5 and 2023 Escalade 6.2 models; when the wiring is chafed, pinched or chewed, as Ford documents on early 2016-2017 Explorer 3.5 EcoBoosts; and on a Hyundai or Kia with a blinking light and P1326, where the dealer's first step is a bearing clearance test.

The five knock-code routes, cheapest first

Route 1 · Software, and a code reported wrong — $0 under warranty

What it is. The engine computer's knock diagnostics are too sensitive, too slow, or simply reporting the wrong code. The fix is a reprogram, and several makers say in writing not to replace parts first.

What the documents say.

🟢 GM 19-NA-032 version 3, 2018 Malibu 1.5. "Malfunction Indicator Lamp (MIL) Illuminated - DTC P0325 and/or P0330 May Set," with lack of power and hesitation once the engine is warm: "This condition may be caused by a software anomaly." The engine computer is reprogrammed; on VIN JF190215 and earlier, the technician also swaps the two knock sensor wires at the computer connector. The bulletin prints engine computer reprogramming coverage of 8 years or 80,000 miles.

🟢 GM 22-NA-229, 2023 Escalade 6.2 (LT4). "Possible Audible Knock Due to Reduced Knock Sensor Detection Capability DTC" — the cause "may be a software diagnostic anomaly in the engine control" "module (ECM) that does not properly detect knock sensor circuit failures except during a high rpm condition drive cycle." And: "If you encounter a vehicle with any of the above DTCs DO NOT replace any parts." The bulletin says the knock may be more noticeable on lower-grade fuel; the fix is software.

🟢 Stellantis 18-025-22 REV. C, 2022 Ram ProMaster 3.6 built on or before 27 May 2022. "When decelerating DTC P0325 can be set and stays on." Software only. 🟢 The 3.0 Hurricane flashes — from 18-071-24 REV. B to 18-071-26 (July 2026) for the 2025 Ram 1500, and parallel bulletins for 2023 and 2024 Wagoneers and Grand Wagoneers — list "P0325-00 - Knock/Combustion Vibration Sensor 1 Circuit" with P0330 and P032A, and reprogram the engine computer; the printed cause is "PCM software."

🟢 Audi 2048391/1, /2 and /4, 2013-2017 A8, S8, S6, S7 and RS 7 4.0. "OBD diagnostics are too sensitive. Replacing the knock sensor will not resolve the customer concern." 🟢 Volkswagen 2069630, 2022-2023 GTI 2.0T: "DO NOT diagnose or replace components due to the above faults before performing the update function as explained in this bulletin." 🟢 MINI N16: in extreme cold, "A DME calibration error in the knock sensor diagnostics results in an increased sensitivity threshold to cold temperatures" — "Do not replace any parts."

🟢 Kia FUE 024, 2010-2011 Soul 1.6, and ENG 146 and ENG 150, 2012-2014 Rio and 2012-2014 Soul 1.6 GDI. P0328 and P0326 cured by engine computer software, with the instruction: "DO NOT replace any parts related to the DTCs mentioned above unless proven to be the cause for the DTC AFTER the reflash has been performed." 🟢 Stellantis, 2017 Fiat 500, 500L, 500X, 124 Spider and Jeep Renegade 1.4 turbo: "P0000-00 - will be displayed but should really be displaying P0326-00" — the flash fixes the label; the later revisions then tell the technician to diagnose P0326 normally.

What the owners report. Software appears less often in the complaints than in the documents. A 2015 Accord owner saw P0328 the day after a recall reprogram of the engine computer. A 2014 Cruze owner with P0324 replaced the sensor and its wiring, then had the dealer program the computer — and the code came back the same evening.

The cheap cause that gets skipped. The software level. A dealer compares it with the latest in minutes; on the vehicles above, it is the repair.

At the shop — say this: "Is there a bulletin or software update for this knock code on my VIN? Several makers say not to replace the sensor before the update — can we do that first?"

Route 2 · The wiring and the connector — $0 to $2,900

What it is. The sensor is fine; the signal never reaches the computer cleanly. A harness chafes on a bracket or a coolant outlet, gets pinched between the engine and the transmission, loses a terminal, or is eaten by rodents. On some engines another sensor shares the harness.

What the documents say.

🟢 Ford 18-2367, 2016-2017 Explorer and Police Interceptor Utility 3.5 EcoBoost, built on or before 30 September 2016. "This may be caused by a wire chafe condition near the knock sensor connector C109." The bulletin applies only if "P0325, P0327, P0330 and/or P0332" are "the only DTCs stored," and the repair is the wire plus "a 63.5 mm (2.5 inch) piece of convoluted tubing over the harness" — with "Drain the cooling system" among the steps, which is why it is a 1.7-hour job for a cheap fix.

🟢 Stellantis STAR case S2008000033 and REV. A. "Symptom/Vehicle Issue: MIL Lamp On, DTC P0325 - Knock Sensor 1 Circuit" — inspect the harness at the rear of the engine "and or the C2" "PCM connector terminal 53 K42 circuit," "and isolate the harness concern as needed, no parts required." The revision's photo shows the knock sensor 1 signal terminal pushed out of the connector because its locking tab was deformed. 🟢 S1908000159 REV. A does the same for P0330 where the harness is pinched between "the transmission bellhousing and engine block." Neither case names the vehicle; NHTSA's index lists Jeep.

🟢 GM emission recall 12292 and 12292A, 2013 Malibu 2.5, about 57,000 vehicles. "The wiring harness connections for the knock sensors may be reversed." The first notice says "No parts are required for this recall"; the revision adds two transmission-mount bolts. Dealers service it "at no charge to customers, regardless of mileage, age of vehicle, or ownership, from this time forward."

🟢 GM PIP5576 and 20-NA-207, 2014-2020 V8 trucks, SUVs, Corvettes, Camaros and the CTS-V. "Condition SES lamp, setting DTC P0333 when shifting the Transmission from park" — "DTC P0333 can set due to voltage from the Transmission park/neutral signal" circuit bleeding into the knock circuit. The check is the engine computer's X2 connector. 🟢 GM PIP5273, 2015 Colorado and Canyon 3.6: for P0326 or P0331 in history only, "check for loose connection at the sensor and check connections at the ECM," and "If no connection concerns are found, at this time , DO NOT replace the knock sensor or the ECM for this code." 🟢 PIP5985, 2023-2024 Colorado and Canyon 2.7: a connector not fully seated.

🟢 Ford special service messages 46906 and 47791, 2015-2019 2.7 EcoBoost F-150, Edge, MKX, Fusion and Continental. P0330 appears "with Diagnostic Trouble Codes (DTCs): P0116, P0117, P0118, P0119, P0217, P0330, P1026, and/or P130D" — and SSM 48991 notes that the coolant sensor shares the knock sensor harness. The earlier messages add: "ECT sensors should not be replaced if damaged wiring is found at or near these connectors."

What the owners report. At least 13 complaints in the sensor and replaced-sensor groups mention rodents or chewing. A 2022 Telluride's dealer found "rodents has chewed through my knock sensor wiring" — about $900, not under warranty. A 2020 F-150 owner reports $1,400 for chewed wiring to the injectors and knock sensor; a 2017 RX hybrid owner was billed $2,900. A 2014 Lexus LS460's harness was chewed along with the sensor and the failure came back twice.

The cheap cause that gets skipped. A look at the harness, the connector and the pin. On the Explorers and the Stellantis cases above it is the diagnosis; on the 2013 Malibu it is a free recall.

Fix it yourself — what to check. Where the sensor wiring is visible, look for chafing at brackets and hot parts, chew marks or droppings, and a connector that is not fully latched.

At the shop — say this: "Before a sensor, can you check the knock sensor harness and connector, including the pin at the engine computer, and is there a bulletin or recall for this code on my VIN?"

Route 3 · Moisture, mounting, and a sensor that hears something real — $0 to a few hundred dollars

What it is. The sensor is healthy but reads wrong because water got into it or its connector, because it is not seated flat against the block, or because it is correctly hearing a real mechanical noise.

What the documents say.

🟢 Maserati DS 25-26, Quattroporte, Ghibli and Levante, V6 and V8. A procedure "for addressing false knock sensor DTCs caused by" moisture: hold 3,000 rpm in park without exceeding 230°F, repeat up to five cycles, and only then replace the sensor — "Claims submitted for unnecessary sensor replacement may be subject to audit." 🟢 Audi 2081342/1, March 2026, V6 TFSI models from 2018 to 2026: the sensor housing absorbs moisture during long standing, such as transport, and the codes clear after an extended drive; the bulletin says replacing parts will not fix it.

🟢 Hyundai 24-EM-010H, December 2024. "Certain Elantra N (CN7 N), Kona N (OS N), and Veloster N (JS N) vehicles may have DTC P1326 set due to water intrusion in the knock sensor connector during heavy rain or car wash conditions." — but "If the vehicle is experiencing any abnormal engine noise, this bulletin does NOT apply." The fix is a new sensor and a spliced connector under "Normal warranty."

🟢 GM PIP5836A, 2022 XT5, XT6, Camaro, Acadia, Colorado and Canyon 3.6. P0331 at low mileage, where replaced sensors have "not tested bad": "At this time, instead of replacing the knock sensor please do following." The technician checks for casting flash on the block touching the sensor. With none, the same sensor goes back — "Re-install knock sensor with bolt torque 25 +/- 4 Nm"; with flash, it is removed and the sensor replaced. 🟢 GM PIP5773B, 2019-2020 Camaro, Equinox and Terrain 2.0: "Perform a visual inspection to make sure the wire harness is connected and the sensor is bolted into place," and "If no trouble found, do not replace any parts." 🟢 GM PIP5529B: loose intake manifold bolts among the causes of knock codes on 2013-2017 four-cylinders.

🟢 When the sensor is right. GM's PIP5251B, 2014-2015 Spark: P0324 from "hydraulic lash adjusters becoming spongy due to lash adjuster oil bleed down" — an engine run-in procedure, then the normal diagnosis. GM's PIP5149B, 2014 Silverado and Sierra 4.3 and 5.3 built before 20 August 2013: a connecting rod striking a piston oil squirter, heard by the sensors, which "MUST HAVE EITHER a P0324 and/or EXCESSIVE Spark RETARD" — and, if the inspection confirms the contact, ends in an engine.

What the owners report. A 2016 Pilot owner's parts-store scan showed "Knock Sensor voltage High" P0328, and the dealer quoted $1,234 for both sensors. A 2018 Sonata owner's shorted sensor after a brushless car wash limited the car to about 50 mph until it was repaired under warranty — the same car-wash pattern Hyundai later described for its N models.

The cheap cause that gets skipped. Time and a dry, hot drive. Two makers tell technicians to try that before a part.

At the shop — say this: "Did this start after rain, a car wash or storage? Is the sensor seated and torqued to spec, and is there any flash on the block under it? If the code is intermittent, can we clear it and drive before replacing anything?"

Route 4 · The sensor itself — $140 to $1,234

What it is. The sensor has failed: an open or shorted element, a cracked housing, heat damage. This is the route most quotes start with. In the documents it is rarely the first step, and in the complaints it is often not the last.

What the documents say. 🟢 Subaru 07-133-18R, 2011-2017 models: a design change — "The knock sensor for DIT engines is now utilized for NA engines to improve durability and resistance to heat," at an unchanged 24 Nm. 🟢 Ford 48991 (49004 and 49407 are similar): on 2.7 and 3.0 EcoBoosts with coolant and knock codes together, "replace the 12A648 ECT sensor and 12A699 knock sensor." 🟢 Kia's P1326 follow-up bulletins (Route 5) replace the knock sensor when the bearing test passes and no newer software exists. 🟢 Stellantis 23-019-25, a 2.0-liter Wrangler bundle for India and Asia Pacific only, replaces the sensor for P0330 with a printed cause of "Manufacturing issue."

What the owners report. 152 complaints fall under a sensor or circuit problem without engine failure, and 160 under a sensor or harness replaced with the problem coming back or the cause lying elsewhere. The Chevrolet Cruze is the most frequent non-Hyundai, non-Kia model in the file, with 19 complaints: a 2017 owner writes "I HAVE CHANGED IT 5 TIMES," a 2018 owner with P0325 says it is "the 3rd time I've replaced this sensor." A 2000 ES300 owner paid $3,600 for sensors, the connecting harness and a transmission rebuild, and saw the problem return within two weeks. On Hyundai and Kia models, 13 reported sensor figures run from $140 to $995.

The cheap cause that gets skipped. A resistance and signal test at the sensor, and the same test at the computer connector. If the sensor tests good and the code is still there, the fault is in between.

Fix it yourself — the honest split. Reading the codes, checking the connector and the oil, and recording when the light comes on are owner jobs. On many V engines the sensors sit in the valley under the intake manifold, where replacing them means removing the intake — hours of labor, new gaskets and torque specs. That is a shop job, and a reason to be sure before it starts.

At the shop — say this: "What test condemned the sensor — resistance, signal, or both — and did you test the wiring back to the computer? If you replace it, please keep the old one and write the test result on the invoice."

Route 5 · On a Hyundai or Kia: the bearing warning (P1326) — $0 in a program to $17,000

What it is. From 2018, Hyundai and Kia installed software on millions of engines that uses the knock sensor to listen for the vibration of a failing connecting rod bearing. When it hears it, it sets P1326, blinks the check engine light and limits the engine so the car can reach a dealer before the bearing fails. It is not a knock sensor fault — though the sensor, its wiring and its connector can still be involved.

What the documents say.

🟢 What it does. "The KSDS detects vibrations indicating the onset of excessive connecting rod bearing wear." When it triggers, "the Malfunction Indicator Lamp (MIL) will blink continuously, and the vehicle will be placed in Limp Home Mode" — Hyundai later called it Engine Protection Mode — and "Engine RPMs will be limited to approximately 1800-2000 RPM. This means the maximum vehicle speed will be limited to approximately 65 mph or less depending on vehicle loading and road conditions." Hyundai adds that a chime sounds on certain vehicles.

🟢 What the dealer does. Kia's follow-up bulletins start the same way: "If DTC P1326 is present, first perform the bearing clearance inspection with the Engine Bearing Clearance Tester device (SST KQ231-2T110QQK)." A failed test means a new long block. A passed test does not: depending on the bulletin, the dealer updates the software, installs a knock sensor extension harness after a wiring check, or replaces the knock sensor. Hyundai's campaign 953 sends a car that sets P132600 to a separate campaign that installs "a wire harness extension or replacement engine based on the inspection results."

🟢 A wire can set it. In April 2019 Kia re-tested cars already waiting at dealers for a new engine (bulletin ENG 205, service action SA379): "As a result of additional field data collection and analysis, the initial diagnosis method has been updated to improve test result accuracy." A failed wiring signal interference check sends the car to a knock sensor extension harness, not an engine. Hyundai's dealer memo the same year says it refined the inspection "to eliminate the interference caused by the wiring harness," and its script for customers says the re-test "narrowed down the repair to a small engine wire harness (and knock sensor) that was picking up interference."

🟢 The sensor is the last branch, not the first. Hyundai's campaign T3G tables for 2011-2019 Sonata, Santa Fe Sport, Santa Fe, Tucson 2.4 and Veloster N include a knock sensor alone as the repair — only after the crankshaft turns, the bearing test passes, there is no abnormal noise and no newer engine software exists — at 1.3 to 2.3 hours of labor. The T6G guide for Hyundai's other engines prints the same line: "REPLACE KNOCK SENSOR + ECM UPDATE (NO)." Hyundai's dealer memos add two warnings: "Clear DTC P1326 with engine ON. P1326 may reset if not cleared with the Engine ON," and if a car passes the bearing test and the code returns, "contact Techline."

🟢 When P1326 comes back after the update. Hyundai 24-EM-002H (2024), superseded by 26-EM-014H (September 2026): "Certain 2016-2021MY Tucson (TL) 2.0L vehicles may experience continued DTC P1326 after the ECU update has been performed per TSB 22-01-028H-1 (or later)." Before any new software the technician checks the oil — "Engine oil must be CLEAN with oil change maintenance work performed within the last 3,000 miles/6 months" — then spark knock from fuel quality or carbon deposits, a sensor installed "on a cleaned casting surface and with the correct tightening torque," and a connector "free of any pin corrosion or intermittent contact concern due to debris/water." If the test drive shows no code, 26-EM-014H says: "Service procedure is now complete, NO update or other steps are required."

🟢 The software was wrong more than once. "KSDS software version installed on 2014-2015MY Optima vehicles before September 7, 2018 has an error and requires the installation of a new corrected software." On 2017-2018 Optima hybrids, Kia's recall letter says the first version "will not correctly detect the vibrations indicating the onset of excessive connecting rod bearing wear in the engine, thus preventing driver warning and the initiation of limp home mode."

🟢 Coverage depends on the software and the oil. Kia's recalls 20V-750, 21V-844 and 23V-877 warrant long-block repairs for connecting rod bearing damage for 15 years or 150,000 miles once the software is installed; Hyundai's campaign 953 extended the warranty "to 10 years and 120,000 miles (up from 100,000 miles) for original and subsequent owners"; Kia's PI1802, PI1803 and PI1805 promised "lifetime engine warranty coverage for this issue only (DTC P1326)" on 2011-2019 Optima, 2012-2019 Sorento and 2011-2019 Sportage (2011-2013 2.0 turbo only) models; Hyundai's TXXI extension made long-block coverage for bearing wear a "Limited Lifetime Warranty" on 2011-2019 Theta II engines — for consumer-owned cars that, in the January 2022 text, "Completed the Knock Sensor Detection System software update (Campaign 953) AND" have P1326 or a bearing concern; the April 2022 revision drops that box. The later Kia bulletins can refuse an engine for "One oil change gap of greater than 14 months and/or 10,500 miles" — but not within a vehicle's first 15,000 miles — and Kia's owner letters warn that "an abusive failure to take the vehicle to a Kia dealer after KSDS activation may void" the extended coverage.

🟢 And the replacements had their own recall. Kia's 18V-907: on engines replaced under warranty, the knock sensor campaign or recall 17V-224, "the high pressure fuel pipe may have been damaged, misaligned or improperly torqued during the engine replacement procedure, allowing fuel to leak, thereby increasing the risk of fire."

What the owners report. 1,107 complaints fall in this group. In 777 the owner describes limp mode, a stall or a marked loss of power, and in 480 the engine failed, was replaced, or was recommended for replacement. The Optima and the Sonata lead with 204 each, then the Soul with 140, the Sorento with 126 and the Tucson with 123. The complaints return to three arguments: whether the software was ever installed on a used car (a 2014 Santa Fe owner who bought the car used writes that "the claim was denied due to the lack of a knock sensor recall being performed"), whether the oil records are complete, and whether a passed bearing test ends the matter. In this group, 52 engine figures run from $3,200 to $17,000, median $7,856, mostly quotes.

The cheap cause that gets skipped. The wiring check, the campaign and the records. Whether the software is on the VIN, and every oil change receipt, decide more of these bills than any part.

Fix it yourself — what to keep. Oil change receipts with dates and mileage, the campaign or recall numbers the dealer applied, and dated photos of the dashboard when the light blinks. Kia's later bulletins require photos of the dipstick and filler cap; bring the car in promptly after the warning, because the dealer can read how long it was driven afterwards.

At the shop — say this: "Is P1326 stored, and is the knock sensor detection software on this VIN — and which version? Please run the wiring interference check and the bearing clearance test and print both results, and tell me which campaign or recall covers the repair if it fails."

The coverage file: which programs are still running in September 2026

The status column is our own calculation from the terms printed in each document, as of September 2026 — not a statement by the manufacturer. Check the exact VIN.

Reading the Hyundai and Kia programs. Three details decide most claims. First, the software: the Kia recall coverage starts "Upon completion of the KSDS software update," and several denials in the complaints turn on a used car that never received it. Second, the records: the later Kia bulletins list oil-change gaps and unrepaired oil consumption as grounds for refusing an engine. Third, the counting: the 15-year Kia terms run from the first date of service, not from the date you bought the car. Two exceptions: Kia's 2020 Sportage letter (PI1806) prints no warranty extension at all, and Hyundai's March 2026 notice for TXXM says that "If your vehicle has not received KSDS, Hyundai will still consider eligibility for the warranty extension for the time being." Hyundai's recalls 20V-746 and 21V-727 inspect the engine and replace it if bearing damage is found, with a new long block within 5 years or 60,000 miles and a remanufactured one, if available, beyond. Our Hyundai and Kia engine guide covers the class settlement and its lifetime short-block benefit.

What 1,554 complaints about knock sensors show

PulsCar went through every complaint in NHTSA's file that names a code from P0324 to P0334 — including spellings with a letter O, a space or a suffix — names P1326, or mentions a knock sensor or KSDS in the spellings we searched: 1,554 complaints. The first search found 1,228. Before writing, a second, independent search of the same file looked for what the first had missed — "knock censor," "nock sensor," "detonation sensor," "knock signal," P1326 written without the words "knock sensor," and the Hyundai-Kia wording for the system, such as "engine protection mode" — and found 322 more; a fact-check sweep then found 4 that named P1326 in unusual spellings. All were added and handled the same way. Each complaint was sorted twice, independently, by the same written rules (the sorting rules), fixed before the sorting started. The two sortings matched on the category for 1,506 of 1,554 (97%), and on whether the engine failed for 1,523 (98%). Every difference was settled by the written rules, and a final check of the agreed sortings against the same rules changed 13 more; the published file carries both original sortings, the final one, and which search found each complaint.

The file belongs to two makers. Kia accounts for 742 complaints and Hyundai for 665 — 1,407 of 1,554. Chevrolet follows with 44, Ford with 21, GMC with 16, Toyota with 11 and Honda with 10. Outside Hyundai and Kia, the Cruze leads with 19 complaints, then the Silverado 1500 with 10 and the F-150 with 7.

The failures are serious. Across all 1,554, complaints describe a stall, limp mode or a marked loss of power in 1,050, and an engine that failed, was replaced or was recommended for replacement in 616. In the replaced-sensor group, 46 also describe an engine that failed, was replaced or was recommended for replacement.

It is getting more frequent, not less. By year received: 13 in 2015, 6 in 2016, 5 in 2017, 15 in 2018, then 99 in 2019, 67 in 2020, 135 in 2021, 218 in 2022, 248 in 2023, 222 in 2024, 294 in 2025 and 232 in 2026 to 21 September. The rise follows the Hyundai-Kia software: 60 of its complaints arrived in 2019, 229 in 2025. The median model year is 2016, and of the 478 complaints that give a mileage, the median is 92,750 miles.

Counting complaints, not cars. Some owners filed more than once, and some complaints are about another system with the knock sensor in passing (the 39 in the last row). Every figure here counts complaints.

What do 1,554 federal complaints about knock sensors show, and why do Hyundai and Kia dominate them? In PulsCar's reading of every complaint that names a knock sensor code or P1326 or mentions a knock sensor, each complaint was sorted twice, independently, by the same written rules, and the two sortings matched on the category for 1,506 of 1,554 (97%). Hyundai and Kia account for 1,407, and 1,107 are about the Knock Sensor Detection System, software that uses the knock sensor to listen for connecting rod bearing wear and sets P1326. In at least 160 complaints a knock sensor or its harness was replaced and the problem came back or lay elsewhere; 152 describe a sensor or wiring fault without engine failure. Complaints describe a stall, limp mode or marked power loss in 1,050 and a failed engine in 616. Only 53 name a P0324-to-P0334 code, and 11 name P0325.

What owners say they paid

We collected every dollar figure for a diagnosis, a knock sensor, its wiring, its software or an engine in the 1,554 complaints — 131 figures, most of them quotes — leaving out rentals, towing, vehicle prices and unrelated repairs, and the full list with ODI numbers and the inclusion rule is published. By purpose:

A diagnosis or a test. $90 quoted to diagnose P0326 on a 2013 Accent after the owner replaced the sensor; $150 to $230 in most reports from Kia and Hyundai dealers; $250 to $800 quoted for oil consumption tests; $350 billed for a bearing clearance test on a 2018 Sonata, plus $175 for the knock sensor software; $3,000 to $4,000 quoted for a diagnostic test on a failed Veloster engine.

A knock sensor. $140 and $320 for a 2020 Optima's two replacements; $301.85 for a 2016 Sportage; $500 for a 2013 Optima; $583 for a 2018 Santa Fe Sport; $600 for a 2018 Sonata after a passed bearing test; $635 plus tax quoted for a 2017 Tucson; $643.90 for a 2012 Santa Fe, 11 months after its software update; $816.22 quoted for a 2017 Tucson; $995 quoted for a 2014 Santa Fe nearly four years after its recall work; $1,234 quoted for both sensors on a 2016 Pilot.

Wiring. About $900 quoted for a 2022 Telluride's chewed knock sensor wiring; $1,400 for a 2020 F-150's wiring to the injectors and knock sensor; $2,900 for a 2017 RX hybrid's harness.

An engine. On Hyundai and Kia models, 60 figures, mostly quotes, from $3,200 — an owner's share offered on a 2019 Tucson engine, with Hyundai paying half — to $20,000 quoted for a 2017 Santa Fe Sport, with a median of $8,000; three owners report paying $7,500 to $9,000, and a 2012 Forte's $15,000 engine was charged to an extended warranty. On other makes, eight figures from $6,000 to $20,000, among them $7,200 offered for a rebuilt engine in a 2014 Silverado and $11,416.06 paid for a used engine in a 2019 A8.

Why the knock code comes back after a new sensor

Because the sensor was not the fault. At least 160 complaints describe a sensor or harness replaced and the problem returning or lying elsewhere. The documents name the elsewheres: 🟢 a pin pushed out of the computer connector and a harness chafed at the back of the engine (Stellantis), a chafe near connector C109 (Ford), wires reversed at the factory (GM), a park-neutral circuit bleeding voltage (GM, P0333), casting flash under the sensor (GM, P0331), moisture (Audi, Maserati, Hyundai), and software (GM, Stellantis, Audi, Volkswagen, MINI, Kia).

Because the sensor was right. A sensor that hears a real knock — spongy lifters, a rod touching an oil squirter, a failing bearing — will keep reporting it. On a Hyundai or Kia, replacing the sensor after a P1326 without the bearing test only silences the warning.

Because the software was wrong. 🟢 Kia's first knock sensor software on 2014-2015 Optimas and 2017-2018 Optima hybrids had errors that needed new versions.

Why does a knock sensor code keep coming back after the sensor is replaced? In PulsCar's reading of 1,554 federal complaints and 527 manufacturer documents, at least 160 complaints describe a knock sensor or its harness replaced and the problem returning or lying elsewhere, and the makers' documents name the reasons. Stellantis traces P0325 to a harness chafed at the rear of the engine and a terminal pushed out of the engine computer connector; Ford traces it on early 2016-2017 Explorer 3.5 EcoBoosts to a chafe near connector C109; GM to software and a pin swap on the 2018 Malibu, reversed connectors on the 2013 Malibu, park-neutral voltage (P0333) and casting flash (P0331); Audi, Maserati and Hyundai to moisture; and GM, Stellantis, Audi and Volkswagen to software. On Hyundai and Kia engines, P1326 is first a bearing warning, though wiring, moisture and the sensor itself can set it. Before another sensor, test the wiring back to the computer.

Can you drive with P0325?

With a steady light and a car that drives normally: gently, for a short time. The engine computer is running safe timing, so expect less power and worse economy, and use at least the fuel grade the maker recommends. Book the diagnosis this week.

Not with a blinking light and limp mode on a Hyundai or Kia. That is the bearing warning. Hyundai calls limp mode a way to reach a dealer; Kia's recall letters say pull over and tow, and warn that an "abusive failure" to come in after it triggers may void the extended coverage. Check the oil level first; low oil with no leak is part of the same story.

Not with a deep knock. A heavy knock that follows engine speed is mechanical. In the complaint file, 616 complaints describe an engine that failed or was condemned, for any reason.

Should you buy a used car with a knock sensor history?

On most makes, it depends on what fixed it. A receipt for a software bulletin, a harness repair or a reconnected pin is a closed file. A sensor replaced two or three times is an open one.

On a 2010-2021 Hyundai or Kia with an engine the campaigns cover, ask for three things. Proof that the knock sensor detection software was installed, and which campaign or recall did it; every oil change record; and the date the car was first put into service, because the 15-year Kia terms count from there. Then run the VIN for open recalls. A used car without the software can be sent to a dealer to have it installed — and some complaints show owners learning only after an engine failure that the previous owner never did.

Clearing P0325 before an inspection

Clearing the code does not clear the cause. Erasing codes resets the readiness monitors, which need days of mixed driving to complete, and a broken knock circuit will set P0325 again. A car presented with too many incomplete monitors can be turned away or failed.

What works instead. Fix the route, clear the code, and drive normally for several days. On the Audi and Maserati moisture cases above, a long hot drive is part of the fix.

What a shop actually does with a knock code, checkpoint by checkpoint

Checkpoint 1: the exact code — P0325 or its family, or P1326, read with a tool that shows maker codes, with freeze frame.

Checkpoint 2: bulletins, recalls and software — by VIN, including Hyundai and Kia campaigns.

Checkpoint 3: the circuit — routing, chafe points, rodent damage, the connector and its pins at both ends.

Checkpoint 4: the sensor — resistance and signal, seating, torque, anything between it and the block.

Checkpoint 5: the engine — oil level and condition; on a Hyundai or Kia with P1326, the bearing test.

Checkpoint 6: the part — only now, with the test that condemned it on the estimate.

Three knock-code traps that cost owners the most

Trap 1: the sensor as the first answer. A new sensor on a chafed wire or a bad pin sets the same code. Lesson: ask for the wiring and the software first; several makers say so in writing.

Trap 2: P1326 treated as P0325. On a Hyundai or Kia, a "knock sensor" quote after a blinking light can silence a bearing warning. Lesson: ask whether P1326 is stored and for the bearing clearance test result.

Trap 3: the missing paperwork. Coverage for Hyundai and Kia engines depends on the software being installed and on oil records. Lesson: keep every receipt, and check a used car's campaign history before you buy it.

Three knock-code quotes, decoded

These are composite scenarios, not individual customers: each combines details from the documents and complaints above.

Scenario 1: 2016 Explorer 3.5 EcoBoost, 88,000 miles, P0325 and P0330, steady light, quote for both knock sensors. The owner asks about Ford's 18-2367. The SUV was built on or before 30 September 2016, the two knock codes are the only codes stored, and the technician finds the chafe near connector C109, repairs the wire and adds the protective tubing. Lesson: when the only codes are knock codes on this SUV, the wire is the first suspect.

Scenario 2: 2016 Kia Sorento 2.4, 118,000 miles, blinking light, limp mode, quote for a knock sensor. The owner asks whether P1326 is stored and whether the knock sensor software is on the VIN. It is P1326; the dealer runs the bearing clearance test, which fails, and files the engine claim with the owner's oil receipts. Lesson: on these engines, the test and the records decide the bill, not the sensor.

Scenario 3: 2018 Chevrolet Malibu 1.5, early VIN, P0325 and P0330 with hesitation when warm, after a shop replaced one sensor. A dealer checks GM's 19-NA-032: the engine computer is reprogrammed and, on VIN JF190215 and earlier, the two knock sensor wires are swapped at the computer connector. Lesson: run the VIN before the second sensor.

The knock-code plan: 10 minutes, today, this week

10 minutes: read the exact code with a tool that shows maker codes; note whether the light is steady or blinking; check the oil; listen for a deep knock.

Today: if you hear a deep knock, have it towed; if the light blinks with limp mode, have it towed to a dealer. Otherwise, run the VIN at nhtsa.gov/recalls and ask for bulletins by number — 18-2367 on a 2016-2017 Explorer 3.5 EcoBoost built on or before 30 September 2016, 19-NA-032 on a 2018 Malibu 1.5, 22-NA-229 on a 2023 Escalade 6.2, the Hurricane flashes on a 2025 Ram 1500 or a 2023-2024 Wagoneer or Grand Wagoneer, emission recall 12292 on a 2013 Malibu 2.5, and on a Hyundai or Kia, the knock sensor campaigns and recalls 20V-746, 20V-750, 21V-727, 21V-844 and 23V-877.

This week: have the wiring, connector and software checked before the sensor, and on a Hyundai or Kia with P1326, the bearing clearance test — and get every test result written on the repair order.

Sources and documents

Primary documents only. Where a claim in this guide is marked 🟢, it rests on one of the items below, and the reference is given so you can pull the document yourself. Claims marked ⚪ are shop-price estimates carried from PulsCar's repair guides — estimates, not measurements from a dataset we own.

1. GM 19-NA-032 versions 2 and 3; 22-NA-229; emission recall 12292 and 12292A; PIP5576 and 20-NA-207 versions 1 and 2; PIP5273; PIP5303 to PIP5303B; PIP5836A; PIP5773B; PIP5985; 24-NA-180 versions 1 and 2; 24-NA-064; PIP5529 to PIP5529B; PIP5251 to PIP5251B; PIP5149 to PIP5149B and service update 13290 and 13290A; PIP5206 and A; PIP5420; PIC5811.
2. Ford 18-2367; 18-2062; special service messages 45853, 46906, 47791, 48991, 49004, 49407 and 45989; 21-2168.
3. Stellantis 18-025-22 REV. B and C; 18-071-24 REV. B, 18-031-25 to REV. C and 18-071-26; 18-004-24 and REV. B, 18-041-26, 18-069-26, 18-086-24, 18-042-26 and 18-070-26; STAR cases S2008000033 and REV. A and S1908000159 REV. A; the 1.4-liter flashes 18-116-16, 18-026-17 and REV. A, 18-118-16, 18-086-17, 18-043-21, 18-119-16, 18-087-17, 18-083-17, 18-059-17 and REV. A; the Alfa Romeo 18-088-19, 18-016-25, 18-017-25, 18-017-21, 18-045-23 and 18-046-23; the WK and WD flashes 18-049-16 to 18-049-20; 23-019-25 to REV. B. Maserati DS 25-26 and RU 23-37.
4. Kia campaign bulletins PI1802 (revisions to Rev 12), PI1802A1, PI1803 (to Rev 6), PI1805 and its Q&A, PI1806, PI2002A and B, PI2101 to PI2108, and their W/X and Y/Z follow-ups, owner letters, dealer notices and renotifications through 2026; ENG 205 and its revision (SA379); SC200, SC218, SC218A, SC218YZ, SC291 and SC291YZ; FUE 024, ENG 146 and ENG 150. Kia recalls 20V-750, 21V-844, 23V-877 and 18V-907 (Part 573 reports, dealer notices, owner letters and completion reports).
5. Hyundai campaign 953 (TSBs 18-01-027 to 20-01-006H and the dealer best-practice guides), campaigns 966 and 982, 22-EM-008H and 22-01-043H (CNDS), 24-EM-010H; campaigns T3G (18-01-032 to 22-01-033H, 20-01-024H to -2) and T6G (21-01-024H, 22-01-023H to -2, 22-01-024H-2, 26-01-033H) and their dealer best-practice guides; warranty extensions TXXC (18-01-035-1, 21-01-002H, 22-EM-002H and -1), TXXI (22-EM-001H and -1) and TXXM (22-EM-006H-1 and -2); 24-EM-002H and 26-EM-014H; Hyundai recalls 20V-746 and 21V-727.
6. Audi 2048391/1, /2 and /4; 2081342/1. Volkswagen 2069630. Bentley 2065398/1 and /2. MINI SI M12 01 13 and SI M12 17 14. Subaru 07-133-18 and 07-133-18R. Volvo, Mercedes-Benz, Porsche, Ducati, Can-Am, Cummins and Freightliner knock sensor notes listed in the published document file.
7. PulsCar analysis of NHTSA public data, September 2026: 1,554 complaints naming a knock sensor code or P1326 or mentioning a knock sensor, sorted twice independently; owner-reported amounts; the document list with read status. How we did it.

For the neighboring pages: Hyundai and Kia engine knocking, engine knocking sound, flashing check engine light and shaking, the P0335 guide, the P0014 guide and the code index.

Methodology. The complaint set is every complaint in NHTSA's file that names a code from P0324 to P0334 (with spellings using a letter O, a space, a two-character suffix or a bare number after "code"), names P1326, or mentions a knock sensor, KSDS or the Hyundai-Kia wording for it in the spellings we searched — 1,554 in all, 322 found by a second, independent search and 4 by a fact-check sweep. Every complaint was sorted twice, independently, by the same written rules, fixed before the sorting (the two sortings matched on the category for 1,506 of 1,554, 97%, and on engine failure for 1,523 of 1,554, 98%), every difference was settled under written rules published with the data, and a final rule check of the agreed sortings corrected 13. Every complaint quoted, and every dollar figure, was checked against the full complaint text. Coverage status is our computation from the printed terms, as of September 2026. Nothing here is a failure rate.

Prices verified July to September 2026 in the repair guides they are carried from, and reviewed quarterly. Technical documents verified September 2026: the 527 documents and recall filings read in full in our published list — among them GM 19-NA-032, 22-NA-229 and emission recall 12292A, Ford 18-2367, Stellantis STAR case S2008000033 REV. A and 18-071-26, Kia PI1802Y/Z and recall 20V-750, Hyundai campaign 953, 24-EM-010H, 24-EM-002H and 26-EM-014H.

Had a knock code fixed by a wire, a connector, a software update or a bearing test — or talked out of a sensor? Email [email protected] with the vehicle, mileage and outcome.