PULSCAR ANALYSIS — P0325 (KNOCK SENSOR 1 CIRCUIT) AND THE HYUNDAI-KIA KNOCK SENSOR DETECTION SYSTEM (P1326) IN NHTSA'S PUBLIC FILES PulsCar analysis of NHTSA public data, September 2026. License: CC BY 4.0. Attribution: "PulsCar analysis of NHTSA public data, September 2026." Published alongside https://www.pulscar.io/blog/p0325-code ------------------------------------------------------------------------------ Prepared September 2026. Source data: NHTSA public flat files (complaints received 2015 to 21 September 2026, 780,071 records; manufacturer communications from January 2015; recalls from 2010) and documents downloaded from static.nhtsa.gov. 1. Complaints (1,554, all read in full, two readers) First search: every complaint whose narrative names a knock sensor code from P0324 to P0334 — matched by regular expression, including a letter O for the zero, a space or hyphen after the P, a two-character suffix, and a bare number after the word "code" — or uses the words "knock sensor" (with common misspellings) or "KSDS": 1,228 complaints. Completeness check: before writing, a second, independent search of the same file looked for what the first had missed — other spellings of the sensor ("knock censor", "nock sensor", "detonation sensor", "knock signal") and P1326 written without the words "knock sensor" (P1326, P132600, "code 1326"), and the Hyundai-Kia wording for the system, such as "engine protection mode". Its matches were read and 322 more complaints were added. During fact-checking, a third sweep of the database found 4 more that name P1326 in unusual spellings ("OBDP1326", "#1326", "code ... 1326"); they were coded the same way. 1,554 in all. The found_by column says which search found each complaint. Coding: the codebook (codebook.txt) was written, dated and hashed before any complaint was read. Two readers coded all 1,554 separately, each from the codebook only, without seeing the other's codes: one category (K Hyundai-Kia knock sensor detection system; D sensor or harness replaced, problem remained; F engine failure with a knock sensor mentioned; S sensor or circuit; O mentioned in passing) and three flags (engine_failed, stall_or_power_loss, sensor_replaced). Agreement: category 1,506 of 1,554 (96.9%), Cohen's kappa 0.93; engine_failed 1,523, kappa 0.96; stall_or_power_loss 1,540, kappa 0.98; sensor_replaced 1,536, kappa 0.96. Every disagreement was read in full and resolved under the written adjudication rules R1-R6 (codebook.txt); a rule sweep of the agreed codes then corrected 13 more, each read in full. The complaints file carries both readers' original codes, the final code, the resolution and the rule applied. Final: K 1,107; D 160; S 152; F 96; O 39. Because K takes precedence, 126 K complaints that also report a replaced sensor are not in D, so 160 is a floor for replaced sensors that did not fix the problem. Engine failed, replaced or recommended for replacement 616; stall, limp mode or marked power loss 1,050; knock sensor replaced 306. P1326 named in 477 (flag recomputed during fact-checking with a stricter pattern: P1326, P01326, P132600, "code(s)/DTC/#" 1326; repair-order op codes such as 8P1326 excluded); a code from P0324 to P0334 named in 53 (P0326 20, P0325 11, P0324 10, P0328 6, P0327 4, P0333 4, P0332 2, P0331 1). One complaint first read as P0329 was removed from the code count: the owner's "0329 (Engine/Fuel Exhaust)" is not a knock code. Makes: Kia 742, Hyundai 665, Chevrolet 44, Ford 21, GMC 16, Toyota 11, Honda 10, and others. Median model year 2016; median reported mileage 92,750 (478 complaints give one). By year received: 2015 13, 2016 6, 2017 5, 2018 15, 2019 99, 2020 67, 2021 135, 2022 218, 2023 248, 2024 222, 2025 294, 2026 (to 21 September) 232. Figures count complaints, not vehicles. 2. Owner-reported amounts (131) Every dollar figure an owner reports for a diagnosis or test (including oil consumption and bearing clearance tests), a knock sensor or its wiring, knock sensor software, or an engine repair, rebuild or replacement, in p0325-owner-reported-amounts.csv, with what it was for, whether the narrative says it was paid, billed, quoted, offered, covered or not stated, and a make group. Excluded: rentals, towing, vehicle prices, repairs of other named parts, owners' own price guesses and totals that mix unrelated work. The first version of this file (76 rows) was found incomplete during fact-checking; it was rebuilt by extracting every dollar mention from all 1,554 narratives and deciding each one under this rule, with each exclusion and its reason recorded. Most figures are quotes, not bills. 3. Manufacturer documents and recall filings (527 distinct, read in full) First search: every manufacturer communication whose NHTSA index summary names a code from P0324 to P0334 or uses the words "knock sensor" or "KSDS" (282 NHTSA records), plus every filing of the six recalls that install or concern the Hyundai-Kia knock sensor detection system or its engine replacements (18V-907, 20V-746, 20V-750, 21V-727, 21V-844, 23V-877). 379 distinct documents and filings were read in full (byte-identical copies, including two pairs of recall filings, are marked as duplicates); 6 filings of 23V-877 are listed as not read, and 3 records have no PDF on NHTSA. Completeness check: a second, independent search of the index added P1326 and the Hyundai-Kia wording that describes the system without the word "knock" ("protect the engine from excessive connecting rod bearing damage", "engine monitoring logic"). It found 149 more records — mostly Hyundai P1326 inspection procedures (campaigns T3G and T6G), warranty extensions (TXXC, TXXI, TXXM) and Kia owner and dealer letters for campaigns PI1802 to PI2108 — plus 2 MINI bulletins on a knock control system fault. After removing byte-identical copies, 148 were new distinct documents, all read in full: 527 in all. One record the check first flagged (Kia VSC166, 10143480) was rejected after reading: NHTSA's summary describes knock sensor software, but the PDF is a paint campaign. Of the 527, 511 are relevant and 16 are not (Infiniti, a BMW transmission bulletin, MINI, Harley-Davidson and filings of 18V-907). 18 documents name P0325 in their own text; none of the 148 added documents does. Relevance per document (direct, listed, related, not relevant) and read status are in p0325-documents.csv. Near-identical Hyundai and Kia letters were read by comparing each against a fully read representative, sentence by sentence, and opening the file wherever they differed. Page images were read where the text layer was empty (flowcharts). Every verbatim quote in the article was checked by script against the document or complaint text. Coverage status in September 2026 is our computation from the terms printed in each document, not a statement by the manufacturer. Limits: complaints over-represent engine failures and denied claims; owners report the diagnosis as they understood it and often call the Hyundai-Kia system "the knock sensor"; searches of NHTSA's index cannot see bulletins whose summary is blank or codes that appear only inside a PDF. Nothing here is a failure rate.