PULSCAR CODEBOOK — P1326 AND THE HYUNDAI/KIA KNOCK SENSOR DETECTION SYSTEM (NHTSA COMPLAINTS, 2015 TO 4 OCTOBER 2026)
Published alongside https://www.pulscar.io/blog/p1326-code . License: CC BY 4.0.

The codebook below was written before any complaint was coded, dated and hashed:
2026-10-07T04:24:35Z  (UTC time of hashing)
e22e729933a273611703a496331a36b564b76634d9bcd233ed7eff26ecf64615  codebook.md

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# Codebook — P1326 / Knock Sensor Detection System complaints (P1326 study)

Written before any complaint in the set was coded.

## Pool (how the complaints were found)
NHTSA complaints received 2015-01-01 to 2026-10-04 (782,908 narratives; 2026-10-04 is the latest
received date in the flat files downloaded 2026-10-07). A complaint is in the pool if its narrative
matches any of these case-insensitive regular expressions:

1. P1326 by any spelling — `(?<![A-Z0-9])P\s?[-.]?\s?[1lI]\s?3\s?2\s?6(?:\s?[-:]?\s?[0O]{2})?(?![0-9])`
   (a space, hyphen or period after the P, a letter l or I for the 1, the Hyundai suffix 00 as
   P132600), or a bare 1326 after a code word:
   `\b(?:code|codes|dtc|dtcs|error|cel|coded|fault)\W{0,6}#?\s?1326\b`.
2. The system's own names, any make — `\bK\.?S\.?D\.?S\b|knock[\s-]*sens[oe]r[\s-]*detect|engine\s+protect(?:ion|ive)\s+mode`
   ("KSDS", "knock sensor detection system/software", "engine protection mode").
3. On a Hyundai, Kia or Genesis: the knock sensor in owners' spellings —
   `kn?ock[\s-]*(?:sens[oe]r|censor|senser|sensing)` — because owners call the KSDS campaign "the
   knock sensor recall/update".
4. On a Hyundai, Kia or Genesis: the KSDS warning described in words — a blinking or flashing
   check-engine light (`(?:blink|flash)\w*\W+(?:\w+\W+){0,4}?(?:check\s+engine|engine\s+light|cel\b|mil\b|engine\s+warning)|(?:check\s+engine|engine)\s+light\W+(?:\w+\W+){0,4}?(?:blink|flash)`)
   together with limp mode or a held engine speed
   (`limp|reduced\s+power|protect\w*\s+mode|safe\s+mode|(?:rpm|rpms)\W+(?:\w+\W+){0,6}?(?:2,?000|1,?800|2k)|(?:2,?000|1,?800|2k)\s*rpm|(?:not|n.t|unable to|wouldn.t|would not|wont|won.t)\s+(?:\w+\s+){0,3}?(?:go|accelerate|exceed|rev)\w*\s+(?:\w+\s+){0,3}?(?:over|above|past|faster|beyond)`).

Background for the reader (not a coding rule): P1326 is a Hyundai and Kia code set by the Knock
Sensor Detection System (KSDS), software that uses the engine's knock sensor to listen for the
vibration of connecting-rod bearing wear. When it triggers, the check-engine light blinks and the
engine is held at a low engine speed ("limp mode", "engine protection mode"). The software was
installed by recalls, product improvement campaigns and service campaigns; owners call it "the
knock sensor update", "knock sensor recall", "knock sensor software" or "KSDS".

For each complaint record exactly one CATEGORY and four yes/no FLAGS.

## RELEVANCE

N — Not about the Knock Sensor Detection System or P1326 on THIS vehicle. Use N when:
    - the match is false ("1326" that is not a code, a different code, a different make's code);
    - the complaint is about an ordinary knock sensor circuit fault (P0325-P0334, a steady light,
      a sensor or wire replaced) with NO mention of P1326, KSDS, the knock-sensor software,
      update, recall or campaign, and NO blinking light with limp mode / held engine speed;
    - a blinking light with limp mode is described but nothing in the complaint ties it to the
      knock sensor, P1326, KSDS, the knock-sensor software/recall/campaign, or to connecting-rod /
      bearing damage, engine knocking or an engine failure;
    - the knock sensor software or campaign is mentioned only in general terms (news, other
      people's cars, a class action in general) with nothing about this vehicle.
    NOT N (relevant) when, on this vehicle: P1326 (or an obvious misspelling of it named as the
    knock-sensor code) was read; KSDS / the knock sensor detection system was named; the
    knock-sensor software update, recall or campaign was performed, offered, missing, refused,
    unavailable or blamed; or the KSDS warning (blinking light + limp mode or held engine speed)
    occurred and is tied to the knock sensor, KSDS, bearings, rods, engine knocking or engine
    failure.

## CATEGORY (one letter) — what was found or done after the P1326 / KSDS event on this vehicle

E — Engine replaced or rebuilt. An engine assembly, long block, short block or sub-engine was
    replaced (new, remanufactured or used), or the engine was rebuilt, or the maker/dealer
    approved, ordered or began the replacement. Whoever paid.
D — Engine damage or engine failure, not (yet) replaced. A dealer, shop or the maker diagnosed
    rod-bearing wear or damage, a failed bearing clearance test, a spun or thrown rod, a seized
    or locked engine, a hole in the block, or said the engine needs replacing (including a quote
    for an engine); OR the engine itself failed on the road (seized, locked up, threw a rod, will
    no longer run because of internal damage, caught fire). An owner's own guess about bearings,
    without a failure or a shop's diagnosis, does not count.
S — Knock sensor or its circuit. The knock sensor, its connector or wiring, or a knock-sensor
    harness extension was replaced or repaired as the repair for the event, without E or D.
O — Another cause. The dealer or shop named and repaired something else as the cause (oil level
    or an oil change, spark plugs, ignition coils, a misfire, fuel, injectors, another sensor, the
    transmission, a vacuum leak), without E, D or S.
M — Software only. An ECU/ECM software update, reflash, KSDS installation or KSDS re-installation
    was the only repair stated, without E, D, S or O.
C — Checked and cleared. The dealer or shop inspected or tested (including a passed bearing
    clearance test) and found no fault, or only cleared the code, with no repair, without E, D, S,
    O or M.
U — No diagnosis or repair stated. The event or the campaign is reported, but nothing was found
    or done yet, or the complaint does not say (pending, not taken in, dealer refused to look,
    waiting for parts, outcome unknown).

Precedence when more than one fits: E, then D, then S, then O, then M, then C, then U.
A finding counts when a dealer, shop, the maker or a test states it, or when the event itself is
unambiguous (an engine that seized or threw a rod). A cause the owner merely guesses at does not
count. Use the final state the complaint reports (if a sensor was replaced and later the engine,
the category is E).

## FLAGS (yes/no)

activation — this vehicle showed P1326 (or an obvious misspelling of it named as the knock-sensor
    code) OR the KSDS warning: a blinking/flashing check-engine light with limp mode, reduced
    power, engine speed held near 1,800-2,000 rpm or speed limited, OR the owner or dealer says
    the knock sensor detection system / "engine protection mode" triggered. A steady light alone,
    or engine knocking alone, is no.

ksds_done — the complaint states that the KSDS / knock-sensor software update (or the campaign or
    recall that installs it) was performed on this vehicle at some point, before or after the
    event. "The update was never done", "dealer could not do it", or silence → no.

covered — the complaint states that Hyundai/Kia or the dealer paid, or agreed to pay, the whole
    repair of the event (engine, sensor, software, other repair) under a warranty, recall,
    campaign, extension, settlement or goodwill, or that the repair was done free. Partial payment
    (owner pays a share) → no. Unknown → no.

denied — the complaint states that Hyundai/Kia or the dealer refused, denied or declined coverage,
    said the repair is not covered, or asked the owner to pay any part of it (including a share
    under partial goodwill), or that the owner paid for the repair of the event themselves.
    (covered and denied can both be yes, e.g. denied first and approved on appeal.)

## OUTPUT

One CSV line per complaint, in the order given, no header line:
`odino,category,activation,ksds_done,covered,denied,note`
category is one letter (N E D S O M C U); flags are yes or no (for N, all four flags are no);
note is at most 15 words, no commas, saying what decided the category.

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ADDENDUM for the second batch (309 complaints added by the completeness audit), written and hashed before that batch was read:
2026-10-07T06:06:27Z  (UTC time of hashing)
678e7aefcebf308e4cca29012d67319c5aa4eea5b44f2d7cc5b7a4192ba2dab9  codebook_addendum.md

# Codebook addendum — second batch (completeness audit), written and hashed before the batch was read

The codebook in codebook.md applies unchanged. This addendum records (1) how the second batch was found and
(2) the written decision rules R1-R17 that were used to resolve disagreements in the first batch. They
clarify the codebook; they do not change a category or a flag.

## Second batch (309 complaints)
An independent audit searched the same complaint file for what the first search missed: P1326 written with a
glued prefix or a letter O ("OBDP1326", "PO1326"), a bare 1326 after other wording, the transposed P1236;
"knock" misspellings and system wording ("knock detection", "knock system", "anti-knock", "knocking sensor");
the KSDS campaigns named in words or numbers together with software or engine wording (campaigns 953, 966, 982,
T3G, T6G, PI1802-PI1806, PI2002, PI2101-PI2108, "product improvement campaign" with an ECU update); "engine
protection mode" and limp mode tied to an update, the knock sensor or bearings; a blinking light with held speed
and knocking. 309 complaints were added. A further 503 that cite only a recall, campaign or extension number
(20V746, 20V750, 21V727, 21V844, 23V877, SC200, SC218, SC291, recall 198, TXXI, TXXM) with no knock-sensor,
software or P1326 wording were NOT added: under the RELEVANCE section a reader cannot tell from such a narrative
that the knock-sensor system is involved.

## Decision rules (from the first batch's adjudication)
R1 activation — limp mode, reduced power, or a held road or engine speed counts as the KSDS warning when the complaint (owner, dealer, scan tool or a maker message) ties it to the knock sensor, P1326, KSDS or the knock-sensor software/update/recall, even if no blinking light is mentioned. Engine knocking or a flashing light alone does not.
R2 covered — an engine (or repair) that the complaint says the maker or dealer replaced or approved under a recall, campaign or warranty, with nothing saying the owner paid any of it, counts as covered.
R3 a repair the dealer ordered or scheduled (a harness, a sensor, software) counts as that repair (S/M/O), as an ordered engine counts as E.
R4 a campaign or recall named only by its number (953, 966, 162, T3G, "ECM recall", "service campaigns") is not identified as the knock-sensor software unless the narrative says so; it does not make ksds_done yes, and a repair "under the campaign" with no description is U.
R5 relevance by the warning — without P1326, KSDS, or knock-sensor software/update/recall/campaign wording, a complaint is relevant only if limp mode, reduced power or a held speed is described AND tied to the knock sensor (a knock-sensor code, diagnosis or replacement), or a blinking light with limp mode is tied to bearings, rods, knocking or engine failure. A blinking light without limp mode, or a knock-sensor diagnosis without limp mode, is N (an ordinary knock-sensor or misfire story). "Weak acceleration", hesitation, stalling or "undrivable" are not limp mode; a car that "decelerated", "slowed down" or "would not go faster than X" on its own is. Also relevant: a complaint in which the knock sensor or its code is named as the reason the engine was condemned or replaced (the sensor acting as the bearing detector).
R6 a code that is not P1326 (P126, P3126, P1236 not named as the knock-sensor code, etc.) is not P1326.
R7 general mentions of recalls, lawsuits or the knock-sensor system that are not about this vehicle do not make a complaint relevant (codebook N, fourth bullet).
R8 "installed a knock sensor" / "installed the knock sensor device" without software, update or program wording is a sensor (S), not the software (ksds_done no).
R9 C (checked and cleared) only when the clearing or the no-fault finding is the last thing reported; if the warning returned and the car is pending with no new finding, the category is U. A repair that was done (S/M/O/E) stays that category even if the problem came back.
R10 denied includes a maker or dealer refusing to inspect, act on or repair the event, a statement that the VIN is not eligible or not in the recall, and "no help" from the maker after a failure.
R11 an owner's own statement or implication that the engine is failing or must be replaced, without a shop's diagnosis or a stated failure (seized, thrown rod, will not run), is not D.
R12 an owner's own reading of program terms ("my engine is not covered by the campaign") without a statement attributed to the maker or dealer, and without the owner paying, does not make denied yes.
R13 a diagnostic fee, or a refused tow or rental reimbursement, does not by itself make denied yes (denied is about the repair of the event).
R14 an ECU/PCM/"system"/"computer" software update done in response to P1326 or to a warning the complaint ties to the knock sensor counts as ksds_done yes.
R15 a repair the owner had done at an independent shop counts as owner-paid (denied yes) unless the complaint says someone else paid.
R16 a maker or dealer approval of an engine replacement that was later withdrawn is D (the final state); an approval with a partial share for the owner is E with denied yes.
R17 a maker's or dealer's refusal of an engine replacement, without a shop's diagnosis of engine damage or a stated failure (seized, thrown rod, will not run or restart), is U, not D.

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DECISION RULES used to resolve disagreements (R1-R17 written during the first batch, R18-R20 during the second; the rule_applied column of the complaints file names the rule for each decision). Text as kept in the working file:

# Adjudication rules (written while reading every disagreement; published in codebook.txt)

R1 activation — limp mode, reduced power, or a held road or engine speed counts as the KSDS warning when the complaint (owner, dealer, scan tool or a maker message) ties it to the knock sensor, P1326, KSDS or the knock-sensor software/update/recall, even if no blinking light is mentioned. Engine knocking or a flashing light alone does not.
R2 covered — an engine (or repair) that the complaint says the maker or dealer replaced or approved under a recall, campaign or warranty, with nothing saying the owner paid any of it, counts as covered.
R3 a repair the dealer ordered or scheduled (a harness, a sensor, software) counts as that repair (S/M/O), as an ordered engine counts as E.
R4 a campaign or recall named only by its number (953, 966, 162, T3G, "ECM recall", "service campaigns") is not identified as the knock-sensor software unless the narrative says so; it does not make ksds_done yes, and a repair "under the campaign" with no description is U.
R5 relevance by the warning — without P1326, KSDS, or knock-sensor software/update/recall/campaign wording, a complaint is relevant only if limp mode, reduced power or a held speed is described AND tied to the knock sensor (a knock-sensor code, diagnosis or replacement), or a blinking light with limp mode is tied to bearings, rods, knocking or engine failure. A blinking light without limp mode, or a knock-sensor diagnosis without limp mode, is N (an ordinary knock-sensor or misfire story). "Weak acceleration", hesitation, stalling or "undrivable" are not limp mode; a car that "decelerated", "slowed down" or "would not go faster than X" on its own is. Also relevant: a complaint in which the knock sensor or its code is named as the reason the engine was condemned or replaced (the sensor acting as the bearing detector).
R6 a code that is not P1326 (P126, P3126, P1236 not named as the knock-sensor code, etc.) is not P1326.
R7 general mentions of recalls, lawsuits or the knock-sensor system that are not about this vehicle do not make a complaint relevant (codebook N, fourth bullet).
R8 "installed a knock sensor" / "installed the knock sensor device" without software, update or program wording is a sensor (S), not the software (ksds_done no).
R9 C (checked and cleared) only when the clearing or the no-fault finding is the last thing reported; if the warning returned and the car is pending with no new finding, the category is U. A repair that was done (S/M/O/E) stays that category even if the problem came back.
R10 denied includes a maker or dealer refusing to inspect, act on or repair the event, a statement that the VIN is not eligible or not in the recall, and "no help" from the maker after a failure.
R11 an owner's own statement or implication that the engine is failing or must be replaced, without a shop's diagnosis or a stated failure (seized, thrown rod, will not run), is not D.
R12 an owner's own reading of program terms ("my engine is not covered by the campaign") without a statement attributed to the maker or dealer, and without the owner paying, does not make denied yes.
R13 a diagnostic fee, or a refused tow or rental reimbursement, does not by itself make denied yes (denied is about the repair of the event).
R14 an ECU/PCM/"system"/"computer" software update done in response to P1326 or to a warning the complaint ties to the knock sensor counts as ksds_done yes.
R15 a repair the owner had done at an independent shop counts as owner-paid (denied yes) unless the complaint says someone else paid.
R16 a maker or dealer approval of an engine replacement that was later withdrawn is D (the final state); an approval with a partial share for the owner is E with denied yes.
R17 a maker's or dealer's refusal of an engine replacement, without a shop's diagnosis of engine damage or a stated failure (seized, thrown rod, will not run or restart), is U, not D.
R18 (second batch) a software, ECU/ECM, "logic" or "engine monitoring" update — named or given only a campaign number — that the narrative ties to the engine (bearing wear, engine failure, engine monitoring or protection, a warning or limp mode, or eligibility for an engine replacement or warranty) identifies the knock-sensor software for relevance and for ksds_done. A campaign or recall number with no update/software wording stays under R4.
R19 the category describes what was found or done after the event. When the knock-sensor software was installed in response to the event, or the complaint reports no event at all, and it is the only repair, the category is M. When it was installed earlier (as a campaign) and nothing has been found or done since the warning or failure, the category is U.
R20 an update the narrative names as an emissions, transmission or other non-engine-protection campaign is not the knock-sensor software under R18.

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POOL HISTORY
- First search (regexes above): 1,457 complaints (466 by the P1326 pattern, 13 by a bare 1326 after a code word, 429 by KSDS wording, 924 by Hyundai/Kia knock-sensor wording, 223 by the Hyundai/Kia blinking-light-plus-limp pattern; a complaint can match several).
- Independent completeness audit (a separate search with no access to the coding): 812 further candidates; 309 whose narratives name the system in words (software or ECU update wording with a campaign, "knock detection", "anti-knock", misspellings, P1326 glued to other text such as OBDP1326 or PO1326, the transposed P1236) were added and coded by two new blind, independent classification passes; 503 that cite only a recall, campaign or extension number (20V746, 20V750, 21V727, 21V844, 23V877, SC200, SC218, SC291, recall 198, TXXI, TXXM) with no knock-sensor, software or P1326 wording were not added, because under the RELEVANCE section a reader cannot tell from such a narrative that the knock-sensor system is involved.
- Final: 1,766 complaints; 1,429 relevant, 337 not relevant.