PULSCAR ANALYSIS - P2138 (THROTTLE/PEDAL POSITION SENSOR D/E VOLTAGE CORRELATION) AND ITS SISTER CODES 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/p2138-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; manufacturer communications; recalls since 2010; investigations) and documents downloaded one at a time from static.nhtsa.gov. 1. Complaints (1,182) First search (971): every complaint whose narrative names P2138 or a sister code (P2135, P2136, P2137, P2139, P2140) 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", "coded" or "fault"), or names the accelerator pedal sensor in owners' words (pedal sensor, pedal assembly, pedal module, accelerator or throttle or gas pedal sensor or assembly, APP sensor, pedal position, pedal potentiometer) together with a word about a fault, a repair or a symptom (reduced power, limp, a code, check engine, wrench, replaced, failed, faulty, defect, no response, stalling, hesitation, correlation, voltage), or names the throttle position sensor (throttle position sensor, TPS, throttle sensor) together with reduced power, limp, correlation, DTC, code or wrench. Second search (211): an independent search of the whole file for what the first one missed, run after the first batch was sorted. It proposed 2,506 more complaints after about 4,300 narratives were read. About 2,080 of them blame a throttle motor or throttle body and name no position sensor, no pedal and no position-signal code; that is a different fault, and an addendum (fixed before the second batch was sorted) left them out. The 211 added were: the accelerator pedal named as the part replaced or blamed, without the word sensor or assembly (110); the throttle position sensor named with a context word the first search did not require (44); the Ford F-150 loss-of-throttle-response group that matches Ford's bulletin SSM 46829 (27); a pedal or throttle sensor circuit code (P2122, P2123, P2127, P2128, P0120 to P0124, P0220 to P0224, P2135 to P2140) in a spelling the first search missed (30). found_by in the complaints file says which search found each complaint. Sorting: the sorting rules (codebook.txt) were written, dated and fingerprinted before any complaint was sorted; an addendum for the second batch was fingerprinted before that batch 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 sorting1 and sorting2). One category (P pedal sensor or assembly; T throttle body or throttle position sensor; W wiring or connector; C computer or software; O another cause; K checked and cleared; U no diagnosis or repair stated; N not a position-signal fault on this vehicle) and four flags (limp, stall, recall, returned). Where the complaint gave the sorter only an excerpt around the matching words, the complete text was used when the excerpt did not decide the question. Agreement over all 1,182: category 1,097 (92.8%); limp 1,137 (96.2%); stall 1,171 (99.1%); recall 1,159 (98.1%); returned 1,139 (96.4%). Settling: every disagreement (179 complaints) was read and settled by one of the written rules R1 to R20, R40 or R41 (listed in codebook.txt); the rule applied is in the rule_applied column. A consistency check then changed 81 rows under the same rules, 57 of them rows on which both sortings had agreed (resolution says "agreed; changed in consistency pass"): one row where a parts-store reading had been counted as a shop diagnosis, and 80 rows where the reduced-power or stall mark was missing although the whole complaint states it (the sorters had seen only a window around the matching words; the check read the whole text of every complaint whose wording pointed to such an event, about 230 complaints). Result: 915 relevant, 267 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 (231 candidate documents, 180 files read, 158 distinct texts) First search: NHTSA's index of manufacturer communications, entries whose summary names P2138 or P2135 to P2140, or names the accelerator pedal sensor, the throttle position sensor, the throttle body or electronic throttle together with a word about a fault, a code, a repair or a software update. 409 index entries matched; 192 were kept. Second search: 39 more documents found by the independent search (pedal and throttle position sensor circuit papers; papers about the throttle motor codes P2101, P2111, P2118 or P2176 alone were left out as a different fault). Download: 52 of the 231 candidate documents have no PDF on NHTSA; one more (10162333, a bus maker's paper) downloaded only in part and could not be opened, so 53 candidates were not read. The other 178 candidates came as 180 files (two documents come as two files each); 179 files carried readable text and one scanned paper (10114175) had none. Exact copies (the same text under another number) account for 22 of the files, leaving 158 distinct documents. Reading: the 180 files fall into 111 groups of near-identical documents (revisions, copies and look-alikes). One representative of each group, 111 in all, was read in full: 76 with a full entry (type, date, vehicles, codes, condition, cause, repair, coverage terms, quotations) and 35 with a compact entry. The other 69 files were compared with their representative line by line. One scanned paper was read from images of its pages. Every verbatim quotation taken from a document was checked against the text of the named document. The document list says, for each file, what was done (column read), which of the codes P2138, P2135 to P2140 (others) and P2122, P2123, P2127, P2128 its own text names, whether it names a pedal sensor, and its relevance (DIRECT: about the target fault; LISTED: a target code is one of many in a list; RELATED: a companion code or the same family of fault; NOT RELEVANT). The code and sensor columns come from a plain text search of the file's own text; for papers with no PDF they are empty. Vehicle years, engines, build dates and coverage terms are as printed in the documents, never taken from NHTSA's index, which expands years. Coverage status "as of September 2026" is the authors' computation from printed terms. duplicate_of marks exact copies (same text as another file); the two second files of a document are listed as the document number followed by -2. 3. Owner-reported amounts (75 figures in 70 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 or quote for diagnosing, repairing or replacing the accelerator pedal sensor or assembly, the throttle body or throttle position sensor, their connector or wiring, the engine computer for this fault, or a diagnostic fee asked for this reduced-power or P2135-P2140 event, on that vehicle. Excluded: mileage written as "NNk"; vehicle value, payments, trade-ins or refund requests; repairs of other systems; totals that mix this fault with other work unless the owner attributes the figure to the pedal or throttle part; restatements of a figure already counted in the same complaint; hypothetical figures and other owners' costs. Status comes from the owner's own words (paid, billed, quoted, offered, not stated). 112 candidate figures were found and 37 were excluded; each exclusion and its reason was recorded. 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 (for example how many pedal replacements were followed by a return of the problem) describe the complaints, not all cars. The document set holds what NHTSA's index lists; a maker paper that is not in the index is not in it, and 53 candidate documents could not be read because NHTSA has no PDF for them or the file was incomplete. Complaints that blame a throttle motor or throttle body for reduced power, with no sensor or pedal wording and no position-signal code, were not sorted (about 2,080 found by the second search), by the addendum: this study covers the position-signal fault, not every cause of reduced power.