PULSCAR ANALYSIS — P0302 (CYLINDER 2 MISFIRE DETECTED) 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/p0302-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 (1,334, all read in full, two readers) First search: every complaint whose narrative names P0302 — matched by regular expression after normalising a letter O for the zero and a space or hyphen after the P, including a two-character suffix (P030200, P0302-00) and a bare 302 or 0302 after the words code, dtc, error, cel, fault or trouble — or names cylinder 2 ("cylinder 2", "cyl #2", "#2 cylinder", "no. 2 cylinder", "second cylinder", "2nd cylinder") together with a misfire word: 1,196 complaints. Completeness audit: before writing, an independent audit searched the same file for wordings the first search missed (see "Pool history" in codebook.txt) and read every candidate; 138 genuine misses were added, 1,334 in all. The found_by column says which search found each complaint and, for audit additions, the pattern that found it. Coding: the codebook (codebook.txt) was written, dated and hashed before any complaint was read. Two independent classification passes coded all 1,334 separately, each from the codebook only, without seeing the other's codes (the two passes ran independently of each other). One category (N not relevant; O passing mention; C coolant; V head or valvetrain; R rings or compression; E engine failed, no cause; X another stated cause; D ignition or injector parts replaced, misfire back; G ignition or injector part, no return stated; U no cause stated) and four flags (cyl2_only, list_only, engine_replaced, stall_or_power_loss). Agreement over all 1,334: category 1,140 (85.5%), Cohen's kappa 0.80 (first search alone: 0.87 on 1,196); cyl2_only kappa 0.81; list_only kappa 0.66 (a rare flag, 9 disagreements); engine_replaced 1,262, kappa 0.89; stall_or_power_loss kappa 0.88. Every disagreement (281) was read in full and resolved under the written adjudication rules R1-R10 (codebook.txt); R10 was written after the second reading and applies to the audit additions. A consistency pass then swept the agreed codes by script for contradictions with the rules; 97 candidates were read in full and 3 corrected. The complaints file carries both passes' original codes (coder1_*, coder2_*), the final code, the resolution and the rule applied. Final: not relevant (N) 16; cylinder 2 only inside a copied list (list_only) 13; of the 1,305 that describe a cylinder 2 misfire on the owner's own vehicle: coolant (C) 643, head or valvetrain (V) 150, no cause stated (U) 122, rings or compression (R) 109, ignition or injector parts replaced and the misfire back (D) 85, engine failed with no cause (E) 83, ignition or injector part with no return stated (G) 58, another stated cause (X) 39, passing mention (O) 16. Cylinder 2 the only cylinder named 1,030; engine replaced, recommended or quoted 523; stall, shut-off, limp mode or power loss 408. 451 of the 1,305 name P0302 by code; the rest describe the misfire in words. Makes among the 1,305: Ford 658, Honda 132, Dodge 99, Hyundai 74, Kia 66, Jeep 59, Chrysler 40, Lincoln 35, Chevrolet 31, Toyota 19, GMC 13, Volkswagen 13, and others. Median model year 2017; median reported mileage 83,900 (465 complaints give one). By year received: 2015 19, 2016 22, 2017 23, 2018 27, 2019 71, 2020 79, 2021 77, 2022 102, 2023 160, 2024 246, 2025 269, 2026 (to 21 September) 210. Figures count complaints, not vehicles. 2. Cylinder-number pattern count (not coded) Separately, a script counted across all 780,071 complaints the narratives that contain a misfire word and name exactly one cylinder number (P030x codes or cylinder wording, with written code ranges removed first), grouped by make, model and wording (coolant, head gasket, 1.5, 2.0). It reads words, not diagnoses. 3. Owner-reported amounts (294 figures from 262 complaints) Dollar figures for cylinder 2 diagnoses, ignition parts, injectors, carbon cleaning, heads and head gaskets, valvetrain, rings and engines, decided under one written inclusion rule, in p0302-owner-reported-amounts.csv, with what each was for and whether the narrative says it was paid (75), quoted (205), billed (4), offered (2) or not stated (8). Vehicle prices, towing, rentals, loan balances, unrelated repairs and duplicates are left out; figures from complaints later coded not relevant or list-only were removed. 4. Manufacturer documents (611 read in full) and recall documents First search: every manufacturer communication whose NHTSA index summary names P0302, a misfire code range covering it, or a cylinder 2 misfire, plus the Ford programs 19B37 and 21N12 and Ford recalls 12V-551 and 17V-209, which complaints cite. Completeness audit: an independent audit re-searched the index; it found 8 more documents (earliest revisions of Honda ring extensions, Hyundai and Kia misfire-logic bulletins, a Kia injector-harness note), all read in full. Of 677 records: 611 distinct documents read in full (including 34 recall filings), 60 byte-identical copies (md5) marked as duplicates, 6 with no PDF on NHTSA. Of the 611: 575 relevant, 36 not relevant; 425 name P0302 in their own text (the rest print a range such as P0301-P0304, P030X, or cylinder wording). 20 documents from 12 bulletin families single out a cylinder group containing cylinder 2 in the cause or trigger, or name cylinder 2 as the affected cylinder (cylinder2_specific column); 41 more (Honda ring extensions, Mazda valve-cleaning procedures and its DENSO computer bulletin pairing the cylinder 2 and 3 injector circuits, Kia's injector-harness note) group cylinder 2 only in a procedure or a circuit pairing. Page images were read where the text layer was empty or scrambled; near-duplicate revisions were read as sentence differences against a representative read in full. 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. Added 28 September 2026, after the study set closed: Chrysler warranty bulletin D-14-12 (NHTSA 10069161, June 2014), read in full for the X56 term (10 years or 150,000 miles from the in-service date). It is cited in the article but not counted in the 611 documents or listed in p0302-documents.csv. Limits: complaints over-represent expensive and frightening events; owners report the diagnosis as they understood it; the words "cylinder 2" in a narrative do not prove which cylinder failed; searches of NHTSA's index cannot see bulletins whose summary is blank or whose codes appear only inside the PDF. Nothing here is a failure rate.