P0135 Code in 2026: The O2 Heater, the Fuse It Shares, and the Honda Hybrids Where It Means Injectors

P0135 is usually the cheapest code in this series to get right — and the documents show exactly how owners still get it wrong.

Your engine's upstream oxygen sensor sits in the exhaust before the catalytic converter and tells the computer, many times a second, whether the mixture is rich or lean. It only reads accurately when it is hot, several hundred degrees, and on a cold morning the exhaust takes too long to get it there. So the sensor carries its own small electric heater. P0135 — "O2 Sensor Heater Circuit, Bank 1 Sensor 1," which Chrysler's bulletins call "O2 Sensor 1/1 Heater Performance" — means the computer checked that heater and it did not do its job: the current or resistance was out of range, or the sensor took too long to come up to temperature.

In most cars with P0135 the heater element inside the sensor has simply burned out, and a new sensor ends it. We say that plainly because this guide spends most of its length on the exceptions. They are where the money goes: a fuse the heater shares with other parts, wiring cooked or flooded next to the exhaust, and — on one popular family of new hybrids — a leaking fuel injector that makes the computer misread the heater. We downloaded and read the manufacturer documents on each in full.

The federal complaint file is thin on this code by name. Of 780,071 complaints received by NHTSA from 2015 to September 2026, 5 name P0135 — four of them Chevrolet Volts — and a sixth lists it as "135" in a Volt code list. So we read every one of the 62 complaints that name any oxygen-sensor heater code or describe the sensor heater, and all 41 complaints about injectors on 2023-2026 Honda CR-Vs and Accords, the family whose hybrids Honda's own bulletin ties to P0135 through a leaking injector. Of the 62, 47 are about an oxygen-sensor heater; in 9 an engine fault sat behind the heater code, and in 12 the code was unresolved after new sensors, software or dealer visits.

By the end you will know which of five routes your P0135 is on, what each costs in 2026, which bulletin or warranty applies, and the cheap cause that gets skipped when a sensor is quoted first.

Claims marked 🟢 rest on a bulletin, recall or statute listed in the Sources section; those documents were downloaded and read in full, and the one we could not read is marked. Claims marked ⚪ are shop-price estimates carried from our O2 sensor cost guide. Owner-reported figures are what people told NHTSA, published with ODI numbers. Every complaint counted or quoted below was read in full.

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). A $200 sensor is the right answer to most P0135s; this guide is about the ones where it is not.

What the heater does, and why P0135 is a cold-start code

An oxygen sensor is a ceramic element that produces a signal only when it is hot. On a warm engine the exhaust heats it; on a cold start, without help, it would sit useless for minutes while the engine runs on a fixed, rich default mixture — more fuel, more pollution, and more unburned fuel reaching the catalytic converter. The heater closes that gap: a resistance element inside the sensor, powered through a fuse and switched by the engine computer, brings it up to temperature quickly after a cold start.

The computer watches that heater in two ways, and both can set P0135:

• The electrical check. The heater is a resistor. The computer measures the current it draws or the resistance it presents. An open element, a broken wire, a blown fuse or a short reads out of range.
• The warm-up check. The computer expects the sensor to start switching within a certain time after a cold start. If it does not — because the heater is weak, the exhaust is abnormal, or the sensor is fouled — the heater is blamed.

Neither check proves the heater itself is bad. 🟢 Honda's Service Bulletin 25-044 describes a case where nothing is wrong with the heater at all: on 2023-2025 CR-V Hybrids and Accord Hybrids, "A fuel injector leak causes a rich air/fuel (A/F) mixture that fouls the spark plug(s) and causes the PCM to misread the A/F sensor heater resistance." Its instruction is blunt: "Do not replace the A/F sensor before performing the inspection."

Why this code is worth fixing promptly. A car with a dead upstream heater runs richer than it should every time it starts cold. That costs fuel, and over time the extra fuel washes into the catalytic converter. The sensor is a few hundred dollars; the converter it protects is not.

First: is this really P0135? The heater codes side by side

Heater codes come in a family, and the combination on your scan tool is the first clue.

Three combinations mean three different jobs.

• P0135 alone. Most likely the sensor's heater. Route 3, after a two-minute look at the fuse and connector.
• P0135 with P0141, P0155 or P0161, or with P0030-series codes on more than one sensor. Heaters in different places rarely fail on the same day. A shared fuse, a power feed or a harness is far more likely. Route 1.
• P0135 or P0134 with misfires, rough running, rich codes or a rattle. The heater may be a messenger. Route 4.

The car-level documents follow this logic exactly. 🟢 GM's PIT5336 for 2013-2015 Enclave, Traverse and Acadia lists more than two dozen heater, sensor and purge codes that can set together when the "Emission 1 Fuse is open." 🟢 GM's 21-NA-116 for the 2016-2019 Volt lists nine codes — two of them heater circuit codes — from one blown fuse. 🟢 Ford's 20-2380 lists eight codes, including P0135, P0141, P0155 and P0161, from water in the connectors.

The 10-minute P0135 check

1. Read every code, including pending and history codes, and write down every one in the heater family and every misfire or fuel-trim code.
2. Count the heaters. One heater code is a sensor question; two or more is a power question.
3. Find the fuse. The owner's manual or the fuse box lid names the emission, O2 or engine fuse on many cars. A blown fuse is visible in seconds.
4. Look at the upstream sensor's wiring if you can see it: melted insulation near the manifold, a connector full of water, green crust, a wire rubbing on a bracket or the transmission, rodent damage.
5. Think about recent work. An exhaust, catalytic converter, engine or transmission job near the sensor is a lead.
6. Notice how the engine runs. Rough idle, rattle, misfires or power loss make P0135 a symptom, not a sensor.
7. Run the VIN for bulletins and recalls, and on a Honda hybrid or a Volt, ask the dealer about the bulletin numbers in this guide by name.
8. Do not buy a sensor yet if more than one heater code is stored.

Eight P0135 situations, and which is yours

"A 2023-2025 CR-V Hybrid or Accord Hybrid that rattles when the engine starts, or shakes switching from EV to gas." Honda's injector bulletin. Route 4, and the Honda file.

"A 2016-2019 Volt, 'Propulsion Power Reduced,' heater codes with EGR and purge codes." Fuse F3UA and the EGR valve. Route 1, and the Volt file.

"P0135 and P0141 on the same day." A fuse, a power feed or a harness. Route 1.

"A 2020 F-Super Duty with gas V8, heater and sensor codes on several sensors." Ford's water-in-connector bulletin. Routes 1 and 2.

"A 2010-2012 Ram 2500 or 3500 diesel with O2 sensor codes." Connectors and an overlay harness, before any part. Route 1, and the Ram file.

"P0135 alone, cold starts only, older car, original sensor." The heater element. Route 3.

"P0135 right after exhaust or converter work." A damaged, unplugged or overheated connector. Route 1.

"A new sensor, and the code is back." Route 1, then Route 5, and the section on why.

The P0135 price ladder, from the bottom up

The lower half of that ladder is the right answer for most P0135s. The upper half is what happens when the heater code is the messenger for something else, and it is why this guide asks you to count heater codes and listen to the engine before buying a sensor.

What does it cost to fix P0135 in 2026, and when is a sensor the wrong purchase? Our O2 sensor guide carries $150 to $500 per sensor installed, most jobs $159 to $270, and $150 to $400 for heater-circuit faults. In PulsCar's reading of federal complaints, owners who paid or were quoted for O2 sensors alone name $148 to $1,000 across 17 bills and quotes, with a median of $500. A sensor is the wrong purchase in three documented situations: when more than one heater code sets at once, which GM and Ford trace to a shared fuse or flooded connectors; on a 2016-2019 Chevrolet Volt, where GM's bulletins trace a blown fuse to a shorted EGR valve that owners were quoted $1,927 for as a part and over $4,000 with the cooler; and on a 2023-2025 Honda CR-V Hybrid or Accord Hybrid, where Honda says a leaking injector can set P0135 and forbids replacing the sensor before the inspection.

The five P0135 routes, cheapest first

Route 1 · Fuse, power feed and wiring — before any sensor — $0 to $1,700

The heater draws more current than anything else in the sensor, and its wires run a few inches from the hottest metal under the car. When the power feed fails, every heater on it fails together, and a new sensor cannot help.

What the documents show. 🟢 GM's PIT5336, for 2013-2015 Enclave, Traverse and Acadia with the 3.6L, is the template: a technician may find heater, sensor or purge codes, and "may also find that the Emission 1 Fuse is open." The cause is a harness to the bank 1 sensor "chafing on the A/C hose coupling/connection at the back side of the engine." Repair the wires, insulate them, tie the harness away. 🟢 GM's 21-NA-116 for the 2016-2019 Volt finds "open fuse F3UA in the underhood fuse block" (24-NA-080 calls it a blown F3A fuse) and tells technicians to inspect the harness to the EGR valve, "Heated oxygen sensor 1 (B52A)", the engine coolant thermostat, the EVAP purge valve and the oil pressure control valve — wiring GM says can open that fuse — before replacing the EGR valve. 🟢 Ford's 16-0163 for the 2014-2016 Transit Connect 2.5L finds the engine harness chafing on the transmission 25-30 cm (10-12 inches) below the PCM connector, with a list of codes that includes P0135. 🟢 Ford's 20-2380 traces P0135 and seven other sensor codes on 2020 F-Super Duty 6.2L and 7.3L trucks built on or before 5 June 2020 to "water intrusion into heated oxygen sensor (HO2S) connectors" on the transmission harness. 🟢 Chrysler's 25-004-12 for 2010-2012 Ram 2500 and 3500 Cummins diesels says it plainly: "Do NOT replace any parts prior to performing this bulletin" — which replaces the sensor connectors — and its sister bulletin 25-003-13 found that "Some model year 2011 harness' were built with tin plated terminals in 5 of the connector cavities that should have been gold plated."

What the owners report. A report on a 2020 Explorer, apparently from a shop, "Found massive corrosion at connector" behind a P0161, and "MFG does not have pigtail repair kit available and entire harness would be needed to repair." A 2011 Terrain's cracked exhaust manifold sent hot gas "ON THE WIRES AND HEATER ELEMENT WITHIN THE OXYGEN SENSOR." A 2012 Corolla owner paid $252.59 the second time a clogged air-conditioning drain let water reach the oxygen sensor. A 2014 Camry owner paid $430 for a sensor a rodent had chewed. A 2004 PT Cruiser owner's heater codes went away briefly "BY MESSING WITH THE COMPUTER WIRE LOOM" after new sensors did nothing. And two Ram heavy-duty diesel owners paid $387 and about $1,500 for sensor, wiring and module work that Chrysler's bulletins describe.

The cheap cause that gets skipped. The fuse. It takes a minute to find in the owner's manual and a few seconds to see, and on the Enclave, Traverse, Acadia and Volt it explains every heater code at once. If a new fuse blows again, the short is still there — that is GM's point in telling technicians to walk the harness to each part on the circuit.

Fix it yourself — the honest split. Checking the fuse, looking at the upstream sensor's connector for water or corrosion and following its wires for melted or rubbed insulation are driveway jobs on most cars. So is measuring the heater's resistance at the sensor side of the connector with a multimeter and comparing it with the service manual. Finding an intermittent short in a harness, or building Ford's or Chrysler's harness repairs, is a shop job.

At the shop — say this: "Before you replace the oxygen sensor, can you check the heater fuse, measure power and ground at the sensor connector, and look for chafed or water-damaged wiring? Is there a bulletin on my VIN about the heater circuit or its connectors?"

Route 2 · A bulletin, warranty or campaign on your VIN — $0

No safety recall names P0135 in NHTSA's file. Several bulletins pay for its causes under ordinary warranty, which makes timing everything.

What the documents show. 🟢 Honda's 25-044, July 2025, carries warranty claim information for replacing "fuel injectors and affected spark plug(s)": 2.2 hours on the Accord Hybrid, 2.7 on the CR-V Hybrid. It applies to all 2023-2024 CR-V Hybrids and Accord Hybrids and to 2025 models within listed VIN ranges. 🟢 GM's 21-NA-116 and 24-NA-080 for the Volt give labor operations "For vehicles repaired under warranty." 🟢 Ford's 20-2380 is "Eligible under provisions of New Vehicle Limited Warranty (NVLW)/Emissions Warranty." 🟢 Chrysler's 25-003-13 and 25-002-14 were also released as Rapid Response Transmittal 13-014, and "ALL REPAIRS ARE REIMBURSABLE WITHIN THE PROVISIONS OF WARRANTY." And one bulletin is not a warranty document at all: 🟢 Audi's 2033767/1 for 2010-2012 A6, A7, S4, S5, Q5 and Q7 with P1196, P1197 or P0135 asks dealers to contact its technical assistance center and "Do not delete the DTCs," and says it is "informational only and not applicable to any Audi warranty."

The federal floor. An oxygen sensor is an ordinary emission part. 🟢 42 U.S.C. 7541(i) gives emission-related parts 2 years or 24,000 miles, and reserves 8 years or 80,000 miles for the catalytic converter, the electronic emissions control unit and the onboard diagnostic device. A heater that fails at 30,000 miles is usually a customer-paid part unless a bulletin, a longer new-vehicle warranty or a state program covers it.

What the owners report. Among the 41 Honda complaints, three say their injectors were replaced under warranty. One 2024 CR-V EX-L owner — a trim the bulletin, which covers hybrids, does not list — was quoted about $2,500 at 59,628 miles and told the failure was "normal 'wear and tear'"; a 2023 CR-V owner at about 56,000 miles was told Honda "would not assist in anyway." And one 2024 CR-V owner was refused a warranty repair because the car had not stored a code: "Honda would not honor warranty fix if the car did not store the error code." A 2017 Volt owner found the EGR failure "no longer covered under the vehicle warranty."

The cheap cause that gets skipped. The stored code. Two Honda owners describe a car whose code was gone before the dealer could act on it. If the dashboard warns, do not clear anything; photograph the message, note the time, and take the car in while the code is still stored.

At the shop — say this: "Can you check my VIN for any bulletin about this code or its cause, and tell me whether my remaining new-vehicle, powertrain or emissions warranty covers it? Please record the stored codes and freeze frame on the repair order before you clear anything."

Route 3 · The sensor itself — $150 to $650

After the circuit checks out, the heater element in the sensor is the most common cause of P0135, and replacing the sensor is the right repair.

What the documents show about sensors. They are mostly warnings about replacing good ones. 🟢 FCA's parts note for O2 sensors 68070702, 68142340 and 68070689, about the downstream heater code P0141: "If there is no trouble found, and the fault is stored, DO NOT replace the O2 Sensor," followed by a cold-soak drive procedure. 🟢 Subaru's 09-115-24R, revised April 2025, announces new rear oxygen sensors for 2017-2024 Impreza and Crosstrek, 2019-2023 Forester, 2020-2024 Legacy and Outback 2.5L and 2022-2023 BRZ, with "an optimized coating application to help prevent cracking within the internal surfaces" — and notes "The part numbers have not been changed," so the new sensor is identified by its Denso number. That bulletin covers P0137, P0138, P0140 and P0141, the downstream sensor, not P0135. 🟢 Ford's SSM 50230 fits an updated rear sensor to some 2019-2020 Edge and Nautilus 2.0L for a seal problem. 🟢 Land Rover's SSM72448 on 2016 models says of its heated oxygen sensor codes, "The root cause has yet to be identified."

What the owners report. Across 17 sensor-only bills and quotes, owners name $148 to $1,000, median $500 — higher than our guide's typical shop range, because complaints over-represent dealer bills and repeat repairs. A 2006 Corolla owner reports a sensor "REPLACE 7 TO 10 TIMES" with a heater circuit code that stayed. A 2019 Camry owner's aftermarket sensor failed within days, and the dealer said the car "will not accept after market parts" and quoted about $600 for a genuine one. A 2012 Sentra owner's $70 sensor came out with the threads of the exhaust manifold port, and the fix quoted was a $1,000 manifold. A 2011 Traverse owner declined a $250 dealer quote and had a rear sensor fitted for a total of $30; the light stayed on.

The cheap cause that gets skipped. The part number. A heater that fails a week after installation is often a mismatched or low-quality sensor, and some cars are sensitive to it. Ask for the original-equipment part number or its maker's equivalent, and on a Subaru rear sensor, for the updated Denso number.

Fix it yourself — the honest split. On an engine where the upstream sensor is reachable from above or below, replacing it with an oxygen-sensor socket is a common home job — after the fuse and connector are checked, and with the engine warm enough to ease the threads but cool enough to touch. The honest limit is a sensor stuck in a cast manifold: the Sentra owner's $70 sensor came out with the port's threads, and the quote became a $1,000 manifold; and a shop with heat and thread-repair tools is cheaper than a new manifold.

At the shop — say this: "Before replacing the sensor, can you show me the heater resistance reading at the sensor and the power and ground at the connector? If you replace it, which brand and part number will you fit?"

Route 4 · When the heater code is really an engine or fuel problem — $0 to an engine

A heater code can be the first thing a damaged engine reports, because a sensor soaked in fuel, coolant or oil stops behaving.

What the documents show. 🟢 Honda's 25-044: "The engine runs rough and makes a rattling noise, accompanied by DTC P0134 or P0135." The possible cause is a leaking injector; "Other DTCs may also include: P0700, P0300, P219C, P219D, P219E, P219F, P0172." The inspection is to "Remove and inspect all spark plugs" — if any show a rich condition, "replace the affected spark plug(s) and all fuel injectors." If none do, "Continue with normal troubleshooting for P0134 or P0135."

What the owners report. In the heater-code complaints, 9 of the 47 about an oxygen-sensor heater describe an engine fault behind the code: coolant leaks and head gaskets on a 2016 Edge, a 2015 Fusion and a 2019 Escape — whose owner saw P0141 first, "the heater in 02 sensor is taking too long to warm up," two months before the coolant loss; a long-block replacement estimate on a 2020 Explorer that listed a "BAD HEATER CIRCUIT OXYGEN SENSOR BANK 1 SENSOR 2" line; oil from failed valve seals running into the exhaust of a 2021 Tiguan with a P0030; and timing faults on a 2018 Elantra, a 2011 Acadia and a 2012 Durango. The Honda file below shows what happened to the hybrids.

The cheap cause that gets skipped. Listening. A heater code on a car that runs perfectly is a sensor question; the same code on a car that shakes when the engine starts, rattles, burns coolant or smokes is an engine question, and the cheapest test — pulling the spark plugs, as Honda prescribes — costs far less than the sensor.

At the shop — say this: "The engine also runs rough and rattles. Before replacing the sensor, can you pull and inspect the spark plugs and check for a rich condition, misfire counts and coolant or oil in the exhaust? Does Honda bulletin 25-044 apply to my VIN?"

Route 5 · Software, readiness and "no trouble found" — $0 to $200

The heater is tested in the first minutes after a cold start, which makes it easy to "not find" and easy to "fix" by accident.

What the documents show. 🟢 FCA's procedure for a stored P0141 with no fault found is the clearest description of how the heater test runs: "Clear the P0141 fault. Soak the car for over 6 hours. Turn the key to the 'on' position for 3 seconds (Do NOT crank the engine). Turn the key directly to 'crank'. Test drive the vehicle for two separate 6-minute drive cycles with a 'key-off' in between drive cycles." 🟢 Audi's 2033767/1 asks dealers not to delete P0135 and to attach the diagnostic log to a ticket with its technical assistance center. 🟢 Land Rover's SSM72448 asks retailers to keep replaced sensors for investigation because the root cause is unknown.

What the owners report. A used 2015 Cruze whose buyer found the oxygen sensor and heater monitors "have all been disabled." A 2007 Silverado that failed inspection because the O2 sensor and O2 heater monitors were not ready. A 2024 Wrangler 4xe with P0032 and bucking on the highway, waiting for a software update. A 2017 Malibu with P0036 and P0037 where the dealer "UPDATED THE SOFTWARE" and the problem continued.

The cheap cause that gets skipped. The cold soak. A heater code checked on a warm car in the afternoon may never show itself. Leave the car overnight at the shop, or ask them to follow the manufacturer's drive cycle, before paying for parts.

Fix it yourself — what to note. Whether the code sets only after cold nights, how long the car had been parked, and the outside temperature. On a car being prepared for inspection, a week of normal driving with overnight parking usually lets the heater monitor run.

The Honda hybrid file: a heater code that means a leaking injector

The newest and most expensive P0135 story in the file belongs to two of the best-selling hybrids in the country.

🟢 Honda's Service Bulletin 25-044, dated 8 July 2025, covers the 2023-2024 CR-V Hybrid and Accord Hybrid and early-production 2025 models. Its symptom is "The engine runs rough and makes a rattling noise, accompanied by DTC P0134 or P0135." Its explanation reverses the usual logic of the code: the heater is fine. A leaking injector floods a cylinder, fouls its spark plug, and "causes the PCM to misread the A/F sensor heater resistance." The repair is "the affected spark plug(s) and all fuel injectors" — and, before anything else, "Do not replace the A/F sensor before performing the inspection."

What owners describe. We read every federal complaint about a 2023-2026 CR-V or Accord that mentions an injector: 41, received from July 2023 to September 2026. In 34 the dealer diagnosed or replaced injectors; in the rest an owner suspected them or a dealer could not confirm. 25 say the car is a hybrid or describe the engine starting from electric drive; the others do not say, and at least one names a trim that suggests the non-hybrid engine, which the bulletin does not cover. 17 describe power loss, limp mode or a stall while driving, many on highways — "a critical power failure" at 80 mph on a 2023 CR-V Hybrid with 15,500 miles; an engine that "shut off" at 70 mph in a construction zone on a 2024 CR-V Hybrid with 6,280 miles, later found to have "3 piston cracked." 8 report internal engine damage — cracked pistons, a head gasket, cylinder heads, a short block or a rebuilt engine — and 6 describe trouble continuing after the first repair, including a 2024 Accord "on its 3rd set of injectors within a year." The lowest mileage stated is 230; the highest, 59,628.

What none of them says. Not one of the 41 names P0134 or P0135. Owners report what the dashboard shows — "Emission System Problem," "Power System" warnings, transmission and blind-spot messages at once — and one cites Honda's bulletin by number. That is the practical point of this section: on these cars, the code in the bulletin is invisible to most drivers until a scan tool reads it, and the dashboard message is the earlier warning.

When the warning disappears. Four owners describe a car that stored no code, cleared its own code, or showed no warning at all, and one was refused a warranty repair for that reason. Photograph the dashboard messages, write down the time and mileage, and get the car to a dealer while any code is still stored.

What it costs. Under warranty, the bulletin pays for all injectors and the affected plugs. Outside it, the only figure in the file is a 2024 CR-V EX-L owner's quote of about $2,500 at 59,628 miles — a trim the bulletin does not list. There is no recall or extension for these injectors in NHTSA's files, and no investigation in the investigation file we downloaded in September 2026; the complaints are the record.

The Volt file: one fuse, nine codes and a car that stops

On the 2016-2019 Chevrolet Volt, a heater code that sets alongside EGR, purge and thermostat codes points to a blown fuse and the EGR valve, not the sensor.

🟢 GM's 21-NA-116 (February 2023) describes it: technicians "may find open fuse F3UA in the underhood fuse block" and codes P0030, P0031, P0403, P0405, P0443, P0458, P0489, P0597 and P0598 — the upstream oxygen sensor's heater circuit, the EGR valve, the EVAP purge valve and the thermostat heater. 24-NA-080 (October 2024) calls it a blown F3A fuse and adds P0401. GM names the wiring that can open the fuse; a 2016 Volt owner, below, describes the parts sharing it. The condition "may be caused by an internal short in the exhaust gas recirculation (EGR)," which "could appear to be intermittent if the EGR is not working at the time the fuse is replaced." The correction is to inspect the harness to each of those parts for chafing, and "If the harness checks out, replace the EGR valve." The 2024 version adds that on 2016-2017 cars a plugged EGR cooler can seize the valve, and 🟢 18-NA-089 tells technicians to replace the cooler first when P0401 is the only EGR code.

What owners describe. We found 172 Volt complaints that mention the EGR, all 2016-2018 models. 104 mention "propulsion" — the "Propulsion Power Reduced" message — and 58 mention a fuse. Only 4 name P0135 (one as "135" in a list) and 4 name P0030 or P0031; owners see the propulsion warning, not the code. A 2018 Volt owner's dealer notes are the whole story in one paragraph: codes including P0030, P0031, P0132, P0135 and P0137; "blown 15-amp fuse 3"; bulletin 24-NA-080; "short at the EGR valve." A 2016 Volt owner explains why it matters on the road: the fuse "will also take out the engine oil pressure control solenoid, the evap emission purge solenoid valve, the engine coolant thermostat heater, and the oxygen sensor 1 as they all share the same fuse," and with a flat battery the car is left "unable to move." That owner stopped on a mountain road with no cell signal.

What it costs. Owners were quoted $1,927 for the valve alone, $2,800, and "over $4k" for the valve and cooler, with parts on back order. A new oxygen sensor on a Volt with a blown F3UA fuse fixes nothing; a new fuse lasts until the valve shorts again. Our P0401 guide covers the EGR side in full.

The Ram diesel file: gold terminals, tin terminals, and an overlay harness

On 2010-2012 Ram 2500 and 3500 pickups with the 6.7L Cummins diesel, Chrysler put a whole family of oxygen sensor codes — P0135 among them, as "O2 Sensor 1/1 Heater Performance" — behind the wiring rather than the sensors.

🟢 25-004-12 (December 2012), for trucks built before 4 October 2012, replaces both sensor connectors and says "Vehicles that exhibit ANY DTC('s) (Stored or Active), pertaining to Oxygen Sensors or Oxygen Sensor related components must have this Repair Procedure completed BEFORE any parts are replaced." 🟢 25-003-13 (March 2013) found that some 2011 transmission harnesses had tin-plated terminals where gold was specified at the oxygen sensor module connector, and replaces them by part-number suffix. 🟢 25-002-14 (August 2014) goes further and installs an "Oxygen (O2) Sensor Overlay Harness" — "twelve 18 AWG wires (six from each Oxygen Sensor)" running to a new module connector. The last two were also issued as Rapid Response Transmittal 13-014, reimbursable under warranty.

Owners of these trucks in the file paid $387 for sensor and wiring work that did not end the problem, about $1,500 for a sensor with "OVERLAY HARNESS AND MODULE REPLACEMENT," and one waited a month for back-ordered parts. For a truck of this age out of warranty, the useful thing is the bulletin number: a shop that works through the connectors and the overlay harness first spends less than one that buys sensors.

The Ford file: water, a chafed harness and a build date

🟢 Three of Ford's four documents on this code are about the wires.

• 2020 F-Super Duty, 6.2L or 7.3L gasoline, built on or before 5 June 2020 — TSB 20-2380 and its successor 21-2090 (PDF partly unreadable; NHTSA's summary adds the 10R140 transmission). P0132, P0135, P0138, P0141, P0152, P0155, P0158 and P0161, from "water intrusion into heated oxygen sensor (HO2S) connectors C141, C142, C1571 and/or C1572 on the transmission harness." The repair replaces the transmission harness and the affected sensors, 1.0 to 1.5 hours, under new-vehicle or emissions warranty.
• 2014-2016 Transit Connect 2.5L — TSB 16-0163. A long list of codes including P0131, P0135, P0137 and P0141, from the engine harness chafing on the transmission; repair the wire and tie it away from the sharp edge.
• 2013 Escape, Fusion and MKZ — TSB 14-0129. NHTSA's summary lists P0132, P0135, P0030, P2243 and P2251; the document itself is an image we could not read, so we do not describe its fix.
• 2019-2020 Edge and Nautilus 2.0L built on or before 14 October 2020 — SSM 50230. A rear-sensor seal problem with P0137, P0141 and P2096; an updated sensor.

The build date on the Super Duty bulletin is the kind of detail that decides whether a repair is free. Ask the dealer to check it against your door-jamb label.

The downstream twin: P0141, and Subaru's new rear sensors

P0135 and P0141 are the same fault on the two sides of the catalytic converter, and they are often confused on repair orders. The upstream heater, P0135, matters for fueling; the downstream heater, P0141, matters for the converter test and the inspection. When both set together, the answer is almost always shared power, not two failures. When P0141 sets alone, the documents describe their own set of causes.

🟢 Subaru's 09-115-24R, first issued in May 2024 and revised in April 2025, is the largest of them. It announces "new oxygen sensors developed to address" P0137, P0138, P0140 and P0141 on 2017-2024 Impreza and Crosstrek, 2019-2023 Forester, 2020-2024 Legacy and Outback 2.5L and 2022-2023 BRZ — rear sensors with a coating meant to prevent internal cracking that could cause "short/open circuits." Three details matter to an owner. The new sensor went into production at listed VINs, so a car built later already has it. "The part numbers have not been changed," so a parts counter can hand over an old-design sensor from stock; the new ones are identified by a Denso number engraved on the body, such as 150200-9011 in place of 150200-9010. And the bulletin can be claimed "For vehicles within the Basic New Car Limited Warranty period, applicable emission warranty or covered by an active Subaru Added Security Gold plan," at 1.0 hour for a rear sensor.

🟢 Ford's SSM 50230 fits an updated rear sensor, part K2GZ-9G444-D, to 2019-2020 Edge and Nautilus 2.0L built on or before 14 October 2020 for a seal problem with P0137, P0141 and P2096. 🟢 FCA's parts note is the cautionary one: for a stored P0141 with no fault found, "DO NOT replace the O2 Sensor" — soak the car and drive the cycle.

For a P0135 owner, the lesson is about the pair. If your repair order says "O2 sensor" without a position, ask which one. A downstream sensor fitted for an upstream heater code is a common and entirely avoidable bill.

When the engine is the cause: what the nine complaints show

The nine heater-code complaints with an engine fault behind them fall into three groups, and each has a tell an owner can notice before the bill grows.

Coolant. A 2020 Explorer 2.3L whose long-block estimate listed a bad B1S2 heater circuit, with coolant suspected in two cylinders; a 2016 Edge with P0036 and a coolant leak confirmed by the technician; a 2015 Fusion 1.5L whose owner found the coolant "disappeared" and milky oil, with P0030 and P0141 among the codes; a 2019 Escape whose first code, two months before the coolant loss began, was P0141. Coolant burning in a cylinder reaches the exhaust and the oxygen sensor with it. The tell: a coolant level that keeps dropping with no puddle, white exhaust smoke, or a sweet smell.

Oil. A 2021 Tiguan at 53,000 miles burning a quart per 1,000 miles, with oil "leaking into the exhaust manifold" from valve seals and a sporadic P0030. The tell: topping up oil between changes, or blue smoke at start-up.

Timing and machining. A 2018 Elantra with P0030 among misfire and camshaft codes before an engine replacement; a 2011 Acadia with P0161 pending beside timing chain codes; a 2012 Durango whose B2S1 heater was one line in a list that included a timing chain; a 2014 Grand Cherokee with P0032 whose technician blamed a machining fault in the heads. The tell: a rattle at start-up, a misfire code, or camshaft correlation codes alongside the heater code.

In none of the nine would an oxygen sensor have been the repair, and in two the heater code was the first thing written down. That is the reason this guide asks, in every route, how the engine sounds and runs before a sensor is bought.

What 62 heater-code complaints show

We read all 62 complaints that name an oxygen-sensor heater code or describe the sensor heater. 15 turned out to be about something else — seat heaters that caught fire, cabin heaters, a child seat, a camper, two false code matches. Of the 47 about an oxygen-sensor heater:

The line that matters. In 12 of the 47, new sensors, software or repeated dealer visits did not end the problem, and in 9 more the heater code turned out to be one symptom of an engine fault. The coding has no category for a sensor that fixed it — complaints are written by people whose problem was not fixed, and a $200 sensor that ended a P0135 almost never reaches a federal agency. Read the table as a map of what goes wrong, not of what usually happens.

Which codes. Six name the code: five Volts (one writes it as "135") and a 2006 Mercury Milan whose owner lists it among eleven codes. The rest are the family — P0030, P0031, P0032, P0036, P0037, P0038, P0141, P0155, P0161 — which is why this guide treats them together. The coding is published.

The honest limits. One reader, one pass, no second coder, and at 47 reports, a share near one quarter carries a margin of about 12 points. The file is small because owners rarely write down this code.

What owners say they paid, by lane

Twenty-eight figures (27 shown by lane; one part-only charge of $105 is in the file) from owners who reported oxygen-sensor work or the causes in this guide, every complaint read in full, published with ODI numbers. Bills, quotes and estimates as owners reported them, not invoices.

The figure to remember is the eight in the first row: in eight of the seventeen sensor-only jobs, the owner reports that the light, the stall or the misfire came back. A sensor that is not the fault does not become the fault by being replaced.

Why P0135 comes back after a new sensor

Why does P0135 come back after a new oxygen sensor, and what should be checked before a second one? Usually because the heater circuit, not the heater, was the fault. The heater needs power through a fuse, a ground and intact wires routed near a hot exhaust, and in the manufacturer documents PulsCar read, GM traced heater codes to a blown emission fuse and chafed wiring on the Enclave, Traverse and Acadia and to a shorted EGR valve on a shared fuse on the Volt; Ford to water in connectors on 2020 Super Duty trucks and a chafed harness on the Transit Connect; Chrysler to connector terminals on Ram heavy-duty diesels; and Honda to a leaking injector on 2023-2025 CR-V and Accord hybrids. Before a second sensor, ask for the fuse checked, power and ground measured at the connector, the heater's resistance read at the sensor, the plugs inspected if the engine runs rough, and the VIN checked for bulletins.

Two more reasons appear in the complaints: a low-quality or mismatched replacement sensor, as the Camry owner found; and a code that simply needs a cold start to prove the repair, which a warm test drive cannot show.

Can you drive with P0135?

Usually, yes.

P0135 alone, engine running normally. Drive it, and fix it within weeks. The engine spends longer on its default cold mixture, fuel economy drops, and the car will fail an emissions inspection.

P0135 with several other heater codes. Check the fuse soon. On most cars that is an emissions problem; on a Volt it can be more.

A 2016-2019 Volt with "Propulsion Power Reduced." The shared fuse may have taken the engine offline. With a charged battery you can usually get home; with a flat one, the car may stop. Do not plan a long trip on it.

A 2023-2025 CR-V Hybrid or Accord Hybrid that rattles, shakes or loses power. Get it to a dealer now, and off highways if it loses power.

Can you drive with a P0135 code, and when should you stop? Usually you can drive for days or weeks: the upstream sensor's heater only matters in the first minutes after a cold start, so the engine runs richer than it should until the exhaust warms the sensor, fuel economy suffers and the car will fail an emissions test. The exceptions are the causes behind the code. In the documents PulsCar read, Honda's bulletin 25-044 ties P0134 or P0135 on 2023-2025 CR-V and Accord hybrids to a leaking injector, and in 17 of 41 federal complaints about those cars' injectors owners describe power loss, limp mode or a stall while driving; GM's Volt bulletins trace heater codes to a blown fuse that also serves the EGR valve and purge valve, and owners describe the car stopping in traffic. If the engine shakes, rattles or loses power, or a Volt shows "Propulsion Power Reduced," stop driving it on highways.

Should you buy a used car with a P0135 history?

Usually yes, if the repair order says what was found. A sensor with a part number, a fuse and a shorted component, or a bulletin repair is a closed case; three sensors on one car is an open one. On a 2023-2025 CR-V Hybrid or Accord Hybrid, ask whether bulletin 25-044 was performed and whether all injectors were replaced, and listen to a cold start for a rattle. On a 2016-2019 Volt, ask about the EGR valve and fuse F3UA, and check that the gasoline engine starts and runs when the battery is depleted. On any car, a scan showing the oxygen sensor and heater monitors "not ready" on a car with no codes may mean they were recently cleared.

Clearing P0135 before an inspection

Clearing P0135 resets the readiness monitors, and the heater and oxygen sensor monitors need a cold start and a drive cycle to run again. An inspection station will see "not ready," or the code again if the fault is real, and some states and dealers read the history. Two owners in the file ran into unready or disabled heater monitors, one at inspection and one after buying a used car. Fix the circuit, sensor or cause, let the car sit overnight, drive it normally for several days, and keep the repair order.

What a shop actually does with a P0135, checkpoint by checkpoint

1. Reads every code and the freeze frame, counting heater codes and noting misfire, fuel-trim, EGR and purge codes.
2. Checks the VIN for bulletins and remaining warranty.
3. Checks the heater fuse and, if it is blown, looks for what shorted it.
4. Measures power and ground at the upstream sensor's connector, and the heater's resistance at the sensor.
5. Inspects the wiring and connector for heat, chafe, water and corrosion.
6. Checks the engine — plugs, misfire counts, coolant and oil in the exhaust — when it runs rough.
7. Replaces the sensor with an OE or equivalent part only after the circuit checks out, and records the part number.
8. Verifies with a cold start and the manufacturer's drive cycle, not a warm test drive.

Three P0135 traps that cost owners the most

Trap 1: two sensors for one fuse. When several heater codes set at once, replacing sensors one by one buys parts the car did not need. Lesson: count the heater codes; two or more means the fuse and power feed first.

Trap 2: the sensor on the hybrid that rattles. On a 2023-2025 CR-V or Accord hybrid, Honda says the heater can be misread because of an injector. Lesson: if the engine rattles or shakes, ask for bulletin 25-044 and the plug inspection before any sensor.

Trap 3: the cleared warning. One Honda owner was told the warranty would not pay for a fault the car had not stored. Lesson: photograph the dashboard, do not clear codes, and get the car in while the fault is recorded.

Three P0135 quotes, decoded

These are composite scenarios, not individual customers: each combines details that come up repeatedly in owner reports and shop quotes.

Scenario 1: 2014 Chevrolet Traverse, 128,000 miles, P0030 and P0050 together, quote $640 for two upstream sensors. A second shop finds the emission fuse blown and the harness rubbed through on the air-conditioning hose coupling behind the engine, as GM's bulletin describes. Wire repair, fuse and re-route: about $230. Lesson: two heaters failing on the same day is almost never two sensors.

Scenario 2: 2024 Honda CR-V Hybrid, 21,000 miles, rattle on start, "Emission System Problem," P0135 on the scan, quote $310 for an air/fuel sensor at an independent shop. The owner takes it to a Honda dealer instead. Bulletin 25-044 applies; the plugs show a rich cylinder; four injectors and a plug are replaced under warranty. Lesson: on this car, the sensor quote was the one repair Honda's bulletin forbids first.

Scenario 3: 2009 Toyota Camry, 162,000 miles, P0135 alone on cold mornings, quote $420 at a dealer for a genuine sensor. Fuse and wiring check out; the heater reads open at the sensor. An independent shop fits the same-brand sensor for about $240. Lesson: when the circuit is good, P0135 is the sensor, and the price is where the choice lies.

The P0135 plan: 10 minutes, today, this week

In the next 10 minutes: read every code and count the heater codes; check the fuse; listen to the engine for a rattle or shake; look at the upstream sensor's connector if you can see it.

Today: run the VIN for bulletins and ask the dealer about the numbers in this guide by name — 25-044 on a 2023-2025 Honda hybrid, 21-NA-116 or 24-NA-080 on a Volt, 20-2380 on a 2020 Super Duty, 25-004-12 and 25-002-14 on a Ram heavy-duty diesel; and if the dashboard is warning you, photograph it before anything is cleared.

This week: have power, ground and heater resistance measured before a sensor is bought; ask for the OE or equivalent part number; verify the repair with a cold start; and if a warranty refuses a repair a bulletin describes, write to the manufacturer and file your own NHTSA complaint.

If you are not sure whether a rattle or shake you hear with the code is related, PulsCar's free sound check screens a 30-second recording of your engine. It does not read codes; it is a second opinion on what the engine sounds like.

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. Honda Service Bulletin 25-044, 8 July 2025: DTC P0134 and P0135, Air/Fuel Sensor 1 Heater Malfunction; 2023-2025 CR-V Hybrid and Accord Hybrid (NHTSA 11020826).
2. GM 21-NA-116 and 24-NA-080 (Chevrolet Volt 2016-2019, fuse F3UA and EGR), 18-NA-089 (Volt EGR cooler), PIT5336 (2013-2015 Enclave, Traverse, Acadia; Emission 1 fuse).
3. Chrysler 25-004-12, 25-003-13 and 25-002-14, Rapid Response Transmittal 13-014 (2010-2012 Ram 2500 and 3500 6.7L); FCA parts note on O2 sensors 68070702, 68142340, 68070689 (P0141).
4. Ford TSB 20-2380 and 21-2090 (2020 F-Super Duty 6.2L and 7.3L), TSB 16-0163 (2014-2016 Transit Connect 2.5L), SSM 50230 (2019-2020 Edge and Nautilus); TSB 14-0129 summarized from NHTSA's index only.
5. Audi 2033767/1 (2010-2012 3.0 FSI and 3.2 FSI). Subaru 09-115-24R (rear oxygen sensors). Land Rover SSM72448.
6. 42 U.S.C. 7541(i)(1) and (i)(2): 2 years or 24,000 miles for emission-related parts; 8 years or 80,000 miles for the catalytic converter, electronic emissions control unit and onboard diagnostic device.
7. PulsCar analysis of NHTSA public data, September 2026: 62 heater-code complaints read in full, 41 Honda 2023-2026 CR-V and Accord injector complaints read in full, 172 Chevrolet Volt EGR complaints flagged, 28 owner-reported amounts, and the documents above. Data and method.

For the neighboring codes and costs: O2 sensor replacement cost, P0420 catalytic converter, P0171 and P0174 lean codes, P0300 misfires, P0401 EGR, check engine light on and the code index. For the cars: CR-V, Accord, Ram 1500, Explorer and F-150.

Methodology. The heater-code set is every NHTSA complaint whose narrative names an oxygen-sensor heater code or describes the sensor heater; all 62 were read in full and coded. The Honda set is every 2023-2026 CR-V or Accord complaint mentioning an injector; all 41 were read in full. Volt flags are computed by pattern. Every complaint quoted or counted by hand, and every dollar figure, was read in full. Recall searches cover NHTSA's file from 2010, and manufacturer communications from 2015. Owner figures are not invoices. 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 documents marked as read in our published list — among them Honda 25-044, GM 21-NA-116 and 24-NA-080, Chrysler 25-004-12 and 25-002-14, and Ford 20-2380 — were downloaded from static.nhtsa.gov and read in full on 25 September 2026, when the complaint, recall and bulletin files behind our analysis were also queried.

Had a P0135 fixed by a fuse, a wire, an injector or a bulletin — or refused one? Email [email protected] with the vehicle, mileage and outcome.