PULSCAR ANALYSIS — P0138 (O2 SENSOR CIRCUIT HIGH VOLTAGE, BANK 1 SENSOR 2) 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/p0138-code

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Prepared 27 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 about the downstream oxygen sensor (72, all read in full, two coders)
   Every complaint whose narrative names a downstream-sensor code (P0136 to P0140, P013A to P013F, P0157, P0158, P2270, P2271, with or without a two-character suffix) or contains "downstream" or "rear" followed by O2, 02 or oxygen, "post-cat" or "post catalyst", "bank 1 sensor 2" or "B1S2" (one complaint writes "P136" for P0136 and was matched that way; it turned out to be a knock-sensor code; codes written with a letter O, such as "PO138", are matched the same way). 72 complaints; 11 of them name P0138. The first search did not match codes written with a suffix; one complaint found that way (11585828, "P013A00") was added after the first fact-check as no. 71, and one written with a letter O (11091993, "PO138") after the third as no. 72; both were coded blind by both readers. Two complaints write "P01400" and "P01401", which may be P0140 with a suffix or typing errors; they are not included. Several complaints were matched only through the post-catalyst fuel trim codes P2096/P2097 ("post catalyst fuel trim"); two of them were coded as trim-only (T). Each was read in full and coded by one reader to a written codebook (codebook.txt: one primary category from S, W, M, C, E, T, R, U, N). A second reader coded all 72 independently without seeing the first coding. Agreement on the category: 59 of 72 (81.9%), Cohen's kappa 0.78. The 13 disagreements were resolved by the codebook rules; p0138-72-complaints-read.csv publishes the final category and both coders' original categories (coder1_category, coder2_category) for every complaint, and the resolution column marks the 13.
   Final categories: code named with no diagnosis, or among many codes for another problem (U) 25; the sensor itself (S) 10; the engine computer (M) 8; exhaust or engine behind the reading (C) 7; wiring, connector, harness or contamination (W) 6; recall or coverage program central (R) 6; major engine failure (E) 6; post-catalyst fuel trim codes only (T) 2; not about an oxygen sensor (N) 2.
   Codes named: P0138 11, P0137 9, P0136 4, P2271 3, P2270 2, P0139 2, P013A 2, P0140 1, P0158 1, P0157 1, P013C 1, P013E 1 (one complaint writes "P136" for a knock-sensor code and is not counted as P0136).
   By maker: Chevrolet 20, Kia 10, Toyota 7, Hyundai 5, Nissan 4, three each Ford, Honda, Jeep, Subaru; two each BMW, Chrysler, Dodge, GMC; one each Acura, Audi, Mazda, Mini, Mitsubishi, Suzuki. By year received: 2015 5, 2016 2, 2017 3, 2018 5, 2019 10, 2020 10, 2021 5, 2022 5, 2023 5, 2024 7, 2025 5, 2026 (to 21 September) 10.

2. Owner-reported amounts (20)
   Every dollar figure in the 72 complaints, with what it paid for or was quoted for, in p0138-owner-reported-amounts.csv. Several are not oxygen-sensor repairs (engines, harnesses, an EGR valve); the article groups them by what they paid for.

3. Manufacturer documents (84; 82 read in full)
   Service bulletins, emission recalls, warranty extensions, campaign bulletins, engineering requests and tech tips found through NHTSA's manufacturer-communication index by downstream-sensor codes and descriptions. 82 were downloaded and read in full, including page images where the PDF has no usable text layer (Ford 15-0078, Ford 21-2090, Mazda SA288, Nissan P1A25 and PC857/PM997 announcements); two (Ford 16-0144, Subaru 11-160-15) have no published PDF and are known from NHTSA's summaries. Two pairs are byte-identical copies. 38 name P0138 in their own text (checked by text search, and by page image where there is no text layer). p0138-documents.csv lists every document with its vehicles, what it says, read status and whether it names P0138.
   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 frightening failures, and many of these complaints concern a different, larger problem with an oxygen-sensor code among others; owners report the dealer's diagnosis as they understood it; two coders reduce reading error but do not verify repairs. Nothing here is a failure rate.