PulsCar P0496 / P0443 study: codebook, hashes, interpretation rules and pool history
Published October 2026. Licence CC BY 4.0.

=== HASHES (UTC time of hashing, sha256 of the file shown below) ===
codebook.md   : 2026-10-07T09:55:49Z c0ad81b3beb4ff9fb021041bfbf6b39daf0199da9b0aa875812221baf245c3e2  codebook.md 
addendum      : 2026-10-07T10:47:20Z a4312fdd689b9881317ed170d4003ec314c48d23a1a0e23d176a24b0c15e3074  codebook_addendum.md 
Both files were hashed before any complaint they govern was coded: the codebook before the first of the 200 calibration complaints, the addendum after the completeness audit and before the 985 audit complaints were read.

=== CODEBOOK (as hashed) ===
# Codebook — P0496 / P0443 and the EVAP purge valve, complaints (P0496 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. P0496 or P0443 by any spelling — `(?<![A-Z0-9])P\s?[-.]?\s?[0O]\s?4\s?(?:4\s?3|9\s?6)(?:\s?[-:]?\s?[0O]{2})?(?![0-9])`
   (a space, hyphen or period after the P, a letter O for the zero, a scan-tool suffix 00), or a bare
   496 / 443 after a code word: `\b(?:code|codes|dtc|dtcs|error|cel|coded|fault)\W{0,6}#?\s?0?(?:496|443)\b`.
2. The purge component in owners' words, any make —
   `purge\s*(?:valve|solenoid|control)|canister\s*(?:purge|close|vent)|\bC\.?P\.?V\.?\b|\bPCSV\b|\bCPS\b|purge\s*(?:flow|line|hose)`
   (purge valve, purge solenoid, purge control, canister purge / close / vent valve, CPV, PCSV,
   CPS, purge flow / line / hose).
3. A fuel tank described as collapsed, deformed, crushed or under vacuum AND any tie word in the same
   narrative (`vapor|vacuum|evap|recall|purge|canister|\bvent\b|\bCPV\b`) — tank:
   `(?:fuel|gas)\s*tank\W+(?:\w+\W+){0,6}(?:collaps|implod|crush|deform|caved|vacuum)|(?:collaps|implod|crush|deform|caved)\w*\W+(?:\w+\W+){0,6}(?:fuel|gas)\s*tank`.

Background for the reader (not a coding rule): P0496 means the engine computer sees fuel-vapour flow
through the EVAP purge valve when it has commanded the valve closed (a valve leaking or stuck open).
P0443 means the purge valve's electrical circuit is faulty. The purge valve (also "canister purge
valve", CPV, "purge solenoid") sits between the charcoal canister and the intake; a valve stuck open
can pull engine vacuum into the fuel tank.

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

## RELEVANCE

N — Not about an EVAP purge, vapour-flow or purge-circuit fault on THIS vehicle. Use N when:
    - the match is false: "purge" meaning brake, clutch, coolant, air-conditioning, oil, fuel-line
      or exhaust/DPF purging; "CPS"/"CPV" meaning something else (crank position sensor, a diesel
      part); a crankcase vent valve; a different code;
    - the complaint is about another failure (an engine, a transmission, a recall for another part)
      and a purge part, an EVAP code or the word "purge" appears only inside a list of codes, parts
      or recalls, or as a passing remark, with nothing tying the described event to the purge valve,
      its circuit, purge flow or fuel-vapour vacuum;
    - a fuel tank is described as deformed or collapsed with nothing tying it to the EVAP system,
      vapour, vacuum, purge, a canister or a purge-valve recall/campaign.
    NOT N (relevant) when, on this vehicle: P0496 or P0443 (or an obvious misspelling) was read; the
    purge valve / solenoid / canister vent valve / purge flow was named as the cause, the repair or
    the part to be replaced; a purge-valve recall, campaign, special coverage or bulletin was
    performed, offered, missing, refused, unavailable or blamed; or the tank was deformed/collapsed
    or the engine stalled/would not start after refuelling AND the narrative ties it to the EVAP
    system, vapour, vacuum, purge, canister or such a recall.

## CATEGORY (one letter) — what was found or done about the event on this vehicle

E — Engine harmed. A dealer, shop or the maker states that the purge/vapour fault damaged the engine
    (for example fuel in the cylinders, hydraulic lock, a bent rod), or the engine was repaired or
    replaced and the complaint ties that to the purge/vapour fault. An owner's own guess about
    engine damage, without a shop or maker statement, does not count.
T — Tank, pump, module or canister replaced. A fuel tank, fuel pump, fuel delivery module / sender
    unit or EVAP charcoal canister was replaced, repaired or quoted as the repair for the event
    (including a tank deformed by vacuum that was replaced), without E. Whoever paid; a quote that
    was refused still counts.
V — Purge valve (or its own hose, connector, wiring or fuse) replaced, repaired or quoted/recommended
    by a dealer or shop — also the canister vent solenoid — as the repair for the event, without E or T. A purge-valve recall repair
    that replaces the valve is V.
W — Another EVAP part. A gas cap, filler neck, EVAP hose or line, vent valve, pressure sensor or
    EVAP leak repair was the repair (done or quoted), without E, T or V.
O — Another cause. The dealer or shop named and repaired something that is not part of the EVAP
    system (spark plugs, ignition, a throttle body, a battery, another sensor, a fuel injector,
    the transmission), without E, T, V or W.
M — Software only. A PCM/ECM reprogram, reflash or software update was the only repair stated,
    without E, T, V, W or O.
C — Checked and cleared. The dealer or shop inspected or tested and found no fault, or only cleared
    the code or reset the light, with no repair, without E, T, V, W, 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 T, then V, then W, then O, then M, then C, then U.
A finding counts when a dealer, shop, the maker or a test states it. An owner who writes that THEY
replaced the purge valve themselves counts as V; a cause the owner merely guesses at ("probably the
purge valve") does not count. Use the final state the complaint reports (a valve replaced and later
a tank replaced is T).

## FLAGS (yes/no)

stall — the engine stalled, died, shut off or lost power (while driving, at a stop, idling or at
    start-up after fuelling) as part of the event. A hard start alone, a rough idle alone or a
    warning light alone is no.

refuel — the narrative ties the fault to refuelling or the fuel filler: hard start, long crank,
    stall, rough idle, no start or a stumble after fuelling, a pump nozzle that keeps clicking off,
    or a slow fill. The word "gas station" alone is no.

covered — the complaint states that the maker or the dealer paid, or agreed to pay, the whole repair
    of the event (valve, tank, pump or anything else) under a warranty, recall, campaign, special
    coverage, extension or goodwill, or that the repair was done free. Partial payment (the owner
    pays a share) is no. Unknown is no.

denied — the complaint states that the maker or the dealer refused, denied or declined coverage,
    said the repair is not covered, or asked the owner to pay any part of it, or that the owner
    paid for the repair of the event themselves. (covered and denied can both be yes, for example
    denied first and approved on appeal.)

## OUTPUT

One CSV line per complaint, in the order given, no header line:
`odino,category,stall,refuel,covered,denied,note`
category is one letter (N E T V W 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.

=== ADDENDUM (as hashed; contains rules R1-R18) ===
# Codebook addendum (written 2026-10-07 after the completeness audit and BEFORE any audit complaint was coded)

## Pool additions
An independent audit re-searched the 782,908 complaints (audit/searches.txt) and returned 1,780 candidates the first regexes had missed (purge in other spellings such as "purge vale", "purge canister valve", GM "purge pump", "vapor canister", "evap solenoid", tank collapsed/expanded without a tie word, P1450 / P144A / P0441 and other EVAP codes, vent solenoids, and complaints that cite only a purge-valve recall number).
Rule applied before reading any of them: a candidate is added to the pool if its narrative names a purge-system part, an EVAP fuel-vapour code, a tank collapse or expansion, or a purge-valve recall or campaign number. The one class NOT added is the 795 "stall or no-start after refuelling" candidates (Chrysler, Jeep, Dodge, Ram, Ford, Lincoln, Mercury) whose narratives name no purge-system part, no EVAP code and no recall: under the codebook they are N, because nothing ties the event to the purge valve (they are listed in audit_t2_excluded.json). 985 candidates were added and coded.

## Campaign numbers that are purge-valve or tank-vacuum recalls (so "recall named" can be recognised)
Ford canister purge valve: 18V-735 / Ford 18S32, 19V-515 / 19S22, 26V-369 / 26S40, customer satisfaction 24N07; Ford Fusion and Milan purge valve and tank: 15V-793 / 15S34. Owners also call 18S32 the "fuel tank deformation recall". Hyundai and Kia tank expansion by a damaged check valve in the purge system: 25V-796, 25V-794, Kia SC288 and SC356. GM special coverages and service updates for a purge valve or solenoid that does not close (for example N192210240, N222369620, N232395300, 18029, 13106). A complaint that cites one of these on this vehicle is relevant (rule R16 and R16b below).

## Interpretation rules R1-R18 (written while deciding the first 1,472 disagreements; coders of the audit batch code under the codebook AND these rules)
R1  A diagnosis by a dealer, an independent shop, a parts-store scan or the maker that names the purge valve (solenoid, CPV, purge pump) as the failed part counts as "quoted/recommended" in category V even when no repair is stated. A reading by the owner's own scan tool, an owner's own statement, a hedge ("might be", "probably", "suggested") or a bare code description is U.
R2  A fuel pump, tank or module replaced earlier for a stall that nobody tied to the vapour fault is not category T. T needs a replaced or quoted tank, pump, module, sender or canister that the narrative ties to the purge/vapour fault or to the damage it caused (or that is part of a purge-valve recall remedy).
R3  An owner who bought, ordered or fitted the purge valve themselves is V.
R4  Parts the owner bought or fitted themselves count as "owner paid": denied = yes.
R5  A purge-valve recall or campaign (18V-735 / 18S32, 19V-515 / 19S22, 15V-793 / 15S34, 24N07, 26V-369 and the same-fault GM and Hyundai/Kia programs) named together with the valve or a stuck valve is V, whether the repair was performed, pending or unavailable. A bare recall number or "fuel tank deformation recall" with no valve named is U (see R16).
R6  A canister vent or close valve and vent solenoid, a rollover valve, a purge hose or line, a filler neck, a check valve in the purge system are W (another EVAP part) unless the narrative itself calls the part the purge valve. The charcoal canister itself is T.
R7  C (checked and cleared) needs a stated finding of nothing wrong, "could not replicate", "operating as designed", or only a code cleared. "Inspected, code remains", "mechanics could not identify" and "recall inspection only" are U.
R8  A complaint about another failure (engine, transmission, coolant, turbo, brakes, A/C) in which a purge valve, an EVAP code or "purge" appears only as one item in a list of replaced or broken parts, with no statement that the valve failed or was coded for this event, is N. "Purge valve" inside an air-conditioning part list is an A/C part, not EVAP: N. CPS in these files is usually the crankshaft position sensor: N.
R9  O needs a dealer or shop that names and repairs a non-EVAP cause for the same event. An owner's trial-and-error swap of unrelated parts, a replacement made for a different code or a different recall, or an engine replacement for another defect is not O.
R10 stall = yes when the engine died, shut off, or the narrative says power was lost or the car would not accelerate while driving. A stall caused by another failure in the same narrative (alternator, coolant), a recall letter's generic "may stall", and "almost stalled" with no loss of power are no.
R11 denied = yes when the narrative says the maker or dealer refused, said it is not covered / the car is not in the recall (when a party told the owner), charged a diagnostic fee, or the owner could not afford the quoted repair. A price quote alone, or the owner's own lookup that the VIN is not listed, is no.
R12 covered = yes when a recall or campaign repair or inspection was performed free on this vehicle for this fault (earlier or at this visit), including a reprogram-only recall, or when the maker/dealer agreed to pay. A repair that was only quoted is no.
R13 M (software only) is a recall reprogram or reflash as the only repair stated; if the shop also names the valve as failed, V wins by precedence.
R14 A cracked tank or filler neck with a small-leak code and nothing about purge flow or vacuum is N.
R15 "Replaced several times" with no statement of who paid: denied = no.
R16 A reference to Ford's "fuel tank deformation" recall or campaign numbers on this vehicle ties a tank complaint to the purge-valve recall (relevant, U unless a repair is stated); a collapsed tank with no EVAP, vacuum, purge or recall tie is N.
R16b A purge-valve recall letter or a completed purge-valve recall on this vehicle is relevant (U) even when the described event is something else.
R17 A bare purge-flow or tank-vacuum code (P0441, P1450, P144A) read on this vehicle with nothing else is U, not N.
R18 A purge-valve failure or malfunction stated on this vehicle inside a list of several unrelated failures is relevant (U, or V if a repair is stated).

=== POOL HISTORY ===
First search (2026-10-07): 1672 complaints (R1 code 52, R2 purge-component words 1,522, R3 tank-deformed-with-tie 239; some match more than one).
Calibration: 200 complaints (random.Random(20261007).sample, seed fixed before coding) coded by two independent passes under the same hashed codebook. Adjudicated against the final codes on the 33 disagreements: category accuracy 0.960 and 0.930 (kappa between the two passes 0.852).
Completeness audit (independent search, 82 search calls): 1,780 complaint candidates and 338 document candidates not in the first search. Rule applied before reading them: added when the narrative names a purge-system part, an EVAP fuel-vapour code, a tank collapse or expansion, or a purge-valve recall or campaign number (985 added); NOT added: 795 narratives about a stall or no-start after refuelling that name no purge part, no EVAP code and no recall (listed by the search as one class; under the codebook they are N).
Final pool: 2657 complaints; relevant (not N): 2409.

=== INTERPRETATION RULES USED IN ADJUDICATION (R1-R18) ===
Adjudication rules (written while deciding coder disagreements; the codebook itself was not changed after hashing)

R1  A diagnosis by a dealer, an independent shop, a parts-store scan or the maker that names the purge valve (solenoid, CPV, purge pump) as the failed part counts as "quoted/recommended" in category V even when no repair is stated. A reading by the owner's own scan tool, an owner's own statement, a hedge ("might be", "probably", "suggested") or a bare code description is U.
R2  A fuel pump, tank or module replaced earlier for a stall that nobody tied to the vapour fault is not category T. T needs a replaced or quoted tank, pump, module, sender or canister that the narrative ties to the purge/vapour fault or to the damage it caused (or that is part of a purge-valve recall remedy).
R3  An owner who bought, ordered or fitted the purge valve themselves is V.
R4  Parts the owner bought or fitted themselves count as "owner paid": denied = yes.
R5  A purge-valve recall or campaign (18V-735 / 18S32, 19V-515 / 19S22, 15V-793 / 15S34, 24N07, 26V-369 and the same-fault GM and Hyundai/Kia programs) named together with the valve or a stuck valve is V, whether the repair was performed, pending or unavailable. A bare recall number or "fuel tank deformation recall" with no valve named is U (see R16).
R6  A canister vent or close valve and vent solenoid, a rollover valve, a purge hose or line, a filler neck, a check valve in the purge system are W (another EVAP part) unless the narrative itself calls the part the purge valve. The charcoal canister itself is T.
R7  C (checked and cleared) needs a stated finding of nothing wrong, "could not replicate", "operating as designed", or only a code cleared. "Inspected, code remains", "mechanics could not identify" and "recall inspection only" are U.
R8  A complaint about another failure (engine, transmission, coolant, turbo, brakes, A/C) in which a purge valve, an EVAP code or "purge" appears only as one item in a list of replaced or broken parts, with no statement that the valve failed or was coded for this event, is N. "Purge valve" inside an air-conditioning part list is an A/C part, not EVAP: N. CPS in these files is usually the crankshaft position sensor: N.
R9  O needs a dealer or shop that names and repairs a non-EVAP cause for the same event. An owner's trial-and-error swap of unrelated parts, a replacement made for a different code or a different recall, or an engine replacement for another defect is not O.
R10 stall = yes when the engine died, shut off, or the narrative says power was lost or the car would not accelerate while driving. A stall caused by another failure in the same narrative (alternator, coolant), a recall letter's generic "may stall", and "almost stalled" with no loss of power are no.
R11 denied = yes when the narrative says the maker or dealer refused, said it is not covered / the car is not in the recall (when a party told the owner), charged a diagnostic fee, or the owner could not afford the quoted repair. A price quote alone, or the owner's own lookup that the VIN is not listed, is no.
R12 covered = yes when a recall or campaign repair or inspection was performed free on this vehicle for this fault (earlier or at this visit), including a reprogram-only recall, or when the maker/dealer agreed to pay. A repair that was only quoted is no.
R13 M (software only) is a recall reprogram or reflash as the only repair stated; if the shop also names the valve as failed, V wins by precedence.
R14 A cracked tank or filler neck with a small-leak code and nothing about purge flow or vacuum is N.
R15 "Replaced several times" with no statement of who paid: denied = no.
R16 A reference to Ford's "fuel tank deformation" recall or campaign numbers on this vehicle ties a tank complaint to the purge-valve recall (relevant, U unless a repair is stated); a collapsed tank with no EVAP, vacuum, purge or recall tie is N.
R16b A purge-valve recall letter or a completed purge-valve recall on this vehicle is relevant (U) even when the described event is something else.
R17 A bare purge-flow or tank-vacuum code (P0441, P1450, P144A) read on this vehicle with nothing else is U, not N.
R18 A purge-valve failure or malfunction stated on this vehicle inside a list of several unrelated failures is relevant (U, or V if a repair is stated).

Consistency pass (after both coders and the adjudication): the agreed codes were swept with scripted candidate lists (cons_scan.py, cons_covered.py), each candidate read, and changed under the rules above. 73 category changes (mostly R1 applied to rows where both coders had written U for a dealer or shop diagnosis), covered set to yes on 67 more rows (R12), 8 flag corrections. Every change is listed in adjudication.py (CONS_CAT, COVERED_YES, CONS_FLAGS).