PULSCAR ANALYSIS - P0351 AND P0352 (IGNITION COIL A AND COIL B PRIMARY/SECONDARY CIRCUIT) AND IGNITION COIL COMPLAINTS IN NHTSA'S PUBLIC FILES PulsCar analysis of NHTSA public data, October 2026. License: CC BY 4.0 Attribution: "PulsCar analysis of NHTSA public data, October 2026." Published alongside https://www.pulscar.io/blog/p0352-code ------------------------------------------------------------------------------ Prepared October 2026. Source data: NHTSA public flat files (complaints received 1 January 2015 to 4 October 2026, the latest received date in the files, with the latest complaint we sorted received on 1 October 2026; the index of manufacturer communications; the recalls table) and documents downloaded one at a time from static.nhtsa.gov. The NHTSA complaint file is public: anyone can download it from NHTSA and check any number here against it. 1. Complaints (3,122) Scope: the codes P0351 ("ignition coil A primary/secondary circuit") and P0352 ("coil B"), with the series P0353 to P0358 (coils C to H); ignition coil, coil pack, coil-on-plug, coil boot, and coil connector, wiring or ground complaints described in the owner's words; and ignition-coil recalls and bulletins. First search (2,455): every complaint whose narrative (a) names a code from P0351 to P0358 by any spelling we searched (a letter O for zero, a space, hyphen or period after the P, the suffix 00, or a bare number after "code", "DTC", "error", "CEL" or "fault"), or (b) names the part as a whole (ignition coil, spark coil, coil pack, coil-on-plug, coil boot, "coil and plug", "plugs and coils"), or (c) uses the bare word coil with a misfire word, the word cylinder or a P0xxx code within 70 characters (not when the words nearby show another meaning: coil spring, coil-over, air conditioning, heater, battery, starter, fan, suspension, window, seat). The exact search wording is in codebook.txt. Left out on purpose: the bare word coil with no misfire word, cylinder or code within 70 characters; ignition wires or spark plug wires with no coil named; ignition switch and key complaints. Other misfire codes (P0300 to P0308) are counted here only when the complaint also names a coil or the coil circuit. Independent check (667): a separate search of the whole complaint file for what the first one missed, run after the first batch was sorted. About 4,400 narratives were found by wider wording and about 1,500 passages were read against the same relevance rule; 667 complaints were added (a coil or coils replaced or blamed with the misfire word, cylinder or code farther than 70 characters away; odd spellings such as "ign coil", "ignition.coil", "igniton", "coli pack", "coild"; "COP" and "plug boot"; "ignition pack"; "ignition module" or "ignitor" used in the misfire sense). The search was not stopped by a limit. Of the 667, the sorting counted 647 as relevant. found_by in the complaints file says which search found each complaint ("first search" or "independent check"). Sorting: the sorting rules (codebook.txt) were written, dated and fingerprinted before any complaint was sorted. Every complaint was sorted twice, independently, by the same written rules, each time from the rules alone, without sight of the other sorting (columns first_sorting_ and second_sorting_). One category (C ignition coil; P spark plugs; L leak or contamination at the coil (oil in the plug wells, oil-soaked coil or boot, coolant or water); W circuit (wiring, connector, ground, fuse, module, driver); I injector or fuel; A air, vacuum or sensor; M engine mechanical; F software or campaign only; O another cause; K checked and cleared by a shop; U no diagnosis or repair stated; N not an ignition-coil event of the kind studied) and five flags (stall; flash: a flashing check engine light; recall; returned: the same fault came back after a repair or the repair did not fix it; burn: smoke, a burning smell, a melted or burnt part, arcing or fire tied to the fault). Where the complaint gave the sorting only an excerpt around the matching words, the complete text was used when the excerpt did not decide the question. Agreement of the two sortings over all 3,122: category 90.3% (2,818 of 3,122); stall 96.8%; flash 99.7%; recall 96.0%; returned 94.5%; burn 98.6%. Settling: every complaint on which the two sortings differed in any of the six fields (641 complaints) was settled by one of the written rules listed in codebook.txt; the rule applied is in the rule_applied column. A final check then changed 97 rows under the same rules (the resolution column says "changed in consistency pass"): long narratives were re-read in full where the first sorting was uncertain, and the mark was changed where the whole text says so. Result: 3,010 relevant (2,363 from the first search, 647 from the independent check), 112 not relevant. Counts are counts of complaints, not cars. A complaint is evidence that an owner wrote to NHTSA; nothing here is a failure rate. 2. Documents NHTSA's index of manufacturer communications lists 175 bulletins whose summary names a code from P0351 to P0358 (18 do) or an ignition coil, coil pack, coil-on-plug, coil boot or spark coil. Not all of them could be read. Chosen: 153 (all that are about cars, light trucks and vans; 22 bulletins about heavy trucks, buses, engine makers or motorcycles were set aside and are listed in p0352-documents.csv without a file). The independent check added 40 more bulletins whose summary does not carry the coil wording but whose component tag or text does (plug wire, plug well, "coil - ignition", ignition circuit). Index entries not chosen are not evidence of anything. Files: 193 bulletin files for 193 bulletin numbers in the index (one file each); 94 recall filing files for 6 recall campaigns; 287 files in all (250 distinct documents once the 37 exact copies are set aside). No chosen bulletin lacked a file. Reading: the files fall into groups of near-identical documents (revisions, copies, look-alikes). One representative of each group was read in full; the other files of the group were compared with their representative line by line (171 read in full, 116 compared; 37 of the compared files are exact copies, with the same text as another file, and the rest differ only in details such as a revision date, a model list or a part number, which the comparison recorded). 17 files whose PDF had no readable text were read from images of their pages. Every verbatim quotation was checked against the text of the named document, with the page number. The document list says, for each file, whether it was read in full or compared, which of the codes P0351 and P0352 its own text names (19 files do), whether it names any of P0353 to P0358 (19 files do), and its relevance (DIRECT: about an ignition coil fault or a code of the family; LISTED: a target code is one of many in a list; RELATED: a neighbouring fault, a coil wiring or connector fault, or the same symptom from another cause; NOT RELEVANT). Recalls: 6 recall campaigns were chosen by searching the text of the recalls table (15,291 campaigns) for ignition coil, coil pack, spark plug, plug boot, misfire and igniter wording (the recalls table has no entry that names P0351 or P0352): 11V-004, 15V-559, 19V-743, 21V-264, 23V-564, 26V-493. All 94 filings that NHTSA's recall listing gives for them were downloaded and read. A seventh, 21V-124 (spark plugs, no coil defect named), was set aside. Years and models are as printed in the papers, never from NHTSA's index. Vehicle years, engines, build dates and coverage terms are as printed in the documents. Coverage status "as of October 2026" is our computation from printed terms. duplicate_of marks exact copies (same text as another file). pdf_url is the NHTSA file address on static.nhtsa.gov. 3. Owner-reported amounts (532 figures in 423 complaints) One written inclusion rule (fixed before the figures were decided): a dollar figure is included when the owner states it as a price, charge, bill, quote, estimate or part price for diagnosing or repairing an ignition-coil problem or the misfire, stall or warning light it caused on that vehicle: ignition (coils, coil packs, spark plugs, boots, tune-up); wiring, connectors, grounds, a module, the computer or software tied to the coil circuit; engine work tied to the same misfire (cylinder head, head gasket, coolant leak into a cylinder, short block, long block, engine replacement, valves, an oil leak into the plug wells, valve cover gasket); fuel work tied to it; or a diagnostic fee. Excluded: mileage written as "NNk"; vehicle price, value, payments, trade-in, buyback, refund or reimbursement demands, settlement and lemon-law sums; repairs of other systems (transmission, brakes, A/C, suspension, body) unless the owner ties them to the coil or misfire event; towing and rental-car costs; totals that mix the coil or misfire repair with unrelated work unless the owner attributes the figure to the coil or misfire repair; restatements of a figure already counted in the same narrative; other owners' costs; figures not tied to the coil or misfire event. Status comes from the owner's own words (paid, billed, quoted, not stated); group is coil, tuneup (coils and plugs together, or plugs alone), circuit, engine, mixed (several of these in one price), other or diag (diagnostic fee). 958 candidate figures were found in the 573 relevant complaints that contain a dollar figure and 426 were excluded, each with its reason (p0352-excluded-figures.csv). Figures are what owners wrote, not audited invoices. 4. Limits The complaint file holds the cases where an owner wrote to NHTSA, in the owner's words, with no verification; owners whose trouble ended are mostly not in it. The shares reported describe the complaints, not all cars, and no rate of failure can be computed from them. Only 23 relevant narratives print one of P0351 to P0358 (P0351 in 9, P0352 in 10, P0353 in 9, P0354 in 9, P0355 in 5, P0356 in 4; P0357 and P0358 in none); the rest describe the same coil fault in words, which is why the set is built on wording as well as on codes. The first search did not take the bare word coil without a misfire word, cylinder or code within 70 characters; the independent check read those and added the ones that tie a coil to an engine fault, so a narrative that is not found by either search is not in the set. Complaints that say only "misfire", "rough running" or "ignition system" without naming a coil were left out by rule, and some of them may be the same fault in plainer words. Long narratives were re-read in full where the first sorting was uncertain; a long narrative the first sorting was not uncertain about was not re-read. Category agreement between the two sortings (90.3%) is lower than for the yes/no questions; that is why every disagreement was settled by a written rule and why the article reports the share of complaints where no cause was stated. A part named as the cause is what the owner reports a shop, dealer or mechanic said or did; it is not verified. The document set holds what NHTSA's index lists and what could be read; a maker paper that is not in the index is not in it. Investigation summaries were not part of this set.