PULSCAR CODEBOOK - P0449 AND P0457 (EVAP VENT VALVE CIRCUIT, LEAK DETECTED / FUEL CAP) IN NHTSA COMPLAINTS, 2015 TO 4 OCTOBER 2026
Published alongside https://www.pulscar.io/blog/p0449-code . License: CC BY 4.0.

The codebook below was written before any complaint was coded, dated and hashed:
2026-10-07T09:55:05Z  11708cfaf470a06aa09eea856d789b45ade678abda0b791b29dba852d6ea7c8d  codebook.md  (UTC time of hashing, sha-256, file codebook.md)

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# Codebook — P0449 / P0457 (EVAP vent circuit, leak detected / fuel cap) complaints (P0449 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 the
following case-insensitive regular expressions (R3, R4 and R6 also need their context expression somewhere in the same narrative):

1. R1 - P0449 or P0457 by any spelling (letter O for zero, a space, hyphen or period after the P, suffix 00), or a bare number after a code word:
   `(?<![A-Z0-9])P\s?[-.]?\s?[0O]\s?4\s?(?:49|57)(?:\s?[-:]?\s?[0O]{2})?(?![0-9])`
   `\b(?:code|codes|dtc|dtcs|error|cel|coded|fault)\W{0,6}#?\s?[0O]?4(?:49|57)\b`
2. R2 - the vent valve in owners' words: `(?:vent|venting|ventilation)[\s-]*(?:valve|solenoid)|canister[\s-]*vent|evap\w*[\s-]*vent|\bCVS\b|vent[\s-]*control`
3. R3 - the gas cap or filler neck: `(?:gas|fuel)[\s-]*(?:tank\s+|filler\s+)?cap\b|filler\s+cap|fuel\s+fill(?:er)?\s+(?:inlet|neck|pipe|tube)|filler\s+(?:neck|pipe|tube)|fill\s+(?:neck|inlet)`
   together with a warning/inspection context: `check\s+engine|engine\s+light|\bcel\b|\bmil\b|\bcode|\bdtc|evap|emission|smog|inspection|service\s+engine|warning\s+light|indicator|message|\bloose\b`
4. R4 - the EVAP system: `\bevap(?:orative)?\b|vapor\s+(?:canister|leak|line|recovery)|(?:charcoal|carbon)\s+canister`
   together with a leak/code/light/inspection context: `leak|\bcode|\bdtc|check\s+engine|engine\s+light|\bcel\b|\bmil\b|smog|emission\s+test|inspection|smoke\s+test|\bP0[0-9]{3}|vent|\bcap\b|spider|web\b`
5. R5 - a sibling EVAP code (P0440 P0441 P0442 P0443 P0446 P0447 P0448 P0455 P0456 P0498 P0499): `(?<![A-Z0-9])P\s?[-.]?\s?[0O]\s?(?:440|441|442|443|446|447|448|455|456|498|499)(?:\s?[-:]?\s?[0O]{2})?(?![0-9])`
6. R6 - the spider-web campaigns (`spider`) together with `evap|vent|canister|check engine|fuel`.

Background for the reader (not a coding rule): P0449 is "Evaporative Emission System Vent Valve/Solenoid Circuit
Malfunction"; P0457 is "Evaporative Emission System Leak Detected (Fuel Cap Loose/Off)". The EVAP system traps fuel
vapour in a charcoal canister; a vent valve lets air in and a purge valve lets vapour out to the engine. The gas cap is
the cheapest seal in that system. Owners call these events "check fuel cap", "check fuel fill inlet", "gas cap light",
"EVAP code", "EVAP leak", "emissions light". Companion codes (P0455, P0442, P0456, P0446, P0440, P0496) belong to other
articles but their complaints are in the pool because the owner's question is the same: cap, valve, or something else.

For each complaint record exactly one CATEGORY and four yes/no FLAGS. You see an excerpt around the matching words
(and the whole narrative when nothing matched). Code what the excerpt supports; if it is cut off at a point that
matters, code what is stated.

## RELEVANCE
N - Not an evaporative-system warning event on THIS vehicle. Use N when:
    - the match is false (the words appear in a list of unrelated parts, a different code, a different make);
    - the narrative is only about fuel leaking, spilling or smelling with no check-engine light, EVAP/fuel-cap
      message, code, or failed inspection tied to the EVAP system, cap, filler neck or vent (a cracked tank,
      a fuel-line leak or a cap seal that drips fuel is N unless a warning/code/inspection is tied to it);
    - the narrative is about a purge valve, canister or fuel-pump-module problem (hard start after refuelling, rough
      running) with no EVAP warning, leak code, cap or vent part and no failed inspection;
    - the EVAP words come from another vehicle, a news story or advice, not this vehicle.
    NOT N (relevant) when, on this vehicle: a check-engine light, a "check fuel cap / fuel fill inlet / gas cap"
    message or light, an EVAP or leak code (P0440-P0457 family, P0496-P0499), or a failed emissions test or
    inspection is reported and is tied to the EVAP system, the gas cap, the filler neck, the vent valve or the EVAP
    lines; OR a vent valve, vent solenoid, canister vent line or vent hose defect is described (including the
    spider-web / dust-blocked vent campaigns and fuel spitting back or the pump clicking off because of a blocked
    vent), whether or not a light came on.

## CATEGORY (one letter) - what was found or done, on this vehicle, for the EVAP event

G - Gas cap. The cap was tightened, replaced or reseated and that was stated to be the cause or the fix, or a shop
    or the dealer named the cap (or its seal) as the cause. A cap that was replaced and did NOT fix it is not G.
V - Vent valve / vent solenoid / canister vent line or hose. The vent valve or solenoid, its wiring or connector,
    or the vent line/hose (blocked by spider web, dust, a kinked or disconnected hose) was named as the cause or replaced
    or cleaned as the repair.
F - Filler neck / filler pipe / fuel fill inlet / fuel tank. The filler neck, filler pipe, fuel door/inlet seal, or
    the fuel tank itself (corroded neck, leaking tank, tank seam) was named as the cause or replaced.
H - Other EVAP hardware. Purge valve, charcoal canister, EVAP hoses/lines/pipes, leak-detection pump, fuel tank
    pressure sensor, fuel pump module/flange seal, or "EVAP system" parts in general (the shop replaced "EVAP parts"
    without saying which) were named as the cause or replaced.
S - Software or campaign only. A reflash/recalibration, recall inspection, TSB or special-coverage procedure was
    the only repair stated (no part named as cause).
O - Another cause. A non-EVAP repair was named as the cause (misdiagnosis, a different system), or the light/code was
    traced to something outside the EVAP system.
C - Checked and cleared. The shop or dealer inspected or tested and found no fault, or only cleared the code, with no
    repair; or the light went out by itself and nothing was done.
U - No diagnosis or repair stated. The event is reported but nothing was found or done yet, or the complaint does not say.

Precedence when more than one fits: use the FINAL repair the complaint reports as having fixed it (or, if it never got
fixed, the cause the shop named last). A part replaced that the owner says did not help does not count. If several
parts were replaced together and no single one is named, use the most specific named part in the order F, V, H, G.
Among S, O, C, U: S before O before C before U. A cause the owner merely guesses at does not count (an owner's "probably
the cap" is U unless the cap fix is reported).

## FLAGS (yes/no)

cap_tried - the complaint says the gas cap was tightened, replaced, checked or reseated at some point (by anyone,
    whether or not it helped).
recall - the complaint states that a recall, special coverage, service campaign, extension, TSB or "known issue"
    notice for this vehicle was performed, offered, missing, refused, asked about, or is blamed or credited for this event.
inspection - the complaint states that the vehicle failed, could not take, or could not pass an emissions test, smog
    check or inspection (or was refused a sticker/registration) because of the light or code.
returned - the complaint states that after a repair or a reset the same light, code or message came back, or the
    repair did not fix it.

## OUTPUT

One CSV line per complaint, in the order given, no header line:
`odino,category,cap_tried,recall,inspection,returned,note`
category is one letter (N G V F H S O 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 1 (written after the independent completeness audit and before any audit complaint was coded), dated and hashed:
2026-10-07T11:31:16Z  12d35d2b6d4db7aba8b90cfb8ebd9f2ed4fbed38876c91b73283a732f23610fc  codebook_addendum.md  (file codebook_addendum.md)

# Codebook addendum 1 (completeness audit) - P0449 study

Written after the independent completeness audit (audit/audit_report.md, 2026-10-07) and BEFORE any audit-found complaint was coded. The RELEVANCE rule, the CATEGORY letters, the FLAGS, the precedence rule and the output format of codebook.md are UNCHANGED (including rule revisions R1-R13 decided during adjudication of the first batch, which apply to this batch too).

The audit read about 3,500 narratives outside the first pool and found 937 that meet the unchanged RELEVANCE rule but were not matched by the first-search regular expressions. Reasons it recorded: the EVAP regex needed the literal word "evap" (owners write purge valve, CPV, canister purge, vapor management); the sibling-code list omitted P0444 P0445 P0450-P0454 P0496 P0497 and Ford P1450/P144A and suffix forms such as P045100; the cap regex only knew "fuel fill inlet" and had no lamp/light/icon context; "evaporation", "EVP", "e-vap" are not `\bevap\b`; vent wording covered only vent valve/solenoid, not vent line/pipe/tube/hose, "fuel vent", "tank vent", "venting system", "canister close valve"; failed-inspection wording near a filler tube or canister was missed.

Pool extension (what is added, in plain words): (R7) a purge valve / canister purge / CPV / purge solenoid / vapor management narrative that also reports a check-engine light or a code; (R8) Ford P1450 / P144A / "unable to bleed up fuel tank vacuum" and the EVAP code range P0444 P0445 P0450-P0454 P0496 P0497 P2401-P2422 P04F0 with spelling variants; (R9) "check fuel inlet", gas cap lamp/icon/warning wording, "tighten fuel cap" messages, capless-filler warnings; (R10) "evaporation", "evaporated emissions", "EVP", "e-vap"; (R11) vent line/pipe/tube/hose, fuel vent, tank vent, venting system, tank ventilation, canister close valve; (R12) failed emissions or inspection near filler tube, canister or leak-pump words; (R13) leak-detection pump / NVLD / DMTL and tank collapse or deformation with a check-engine light.

The audit scope decisions are adopted as stated by the audit and recorded here: rollover-valve and liquid/vapor-separator complaints without vent, EVAP or a warning are excluded; recall-notification-only complaints without a warning, code or vent defect are excluded; a purge valve narrative WITHOUT a light or code is excluded. Every audit-found complaint is coded under the same codebook by two blind coders, disagreements decided by the same written rules, found_by = "audit" in the published CSV.

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DECISION RULES used to resolve disagreements (written during adjudication of the first batch and applied unchanged to the audit batch; the rule_applied column of the complaints file names the rule for each decision; R11 was not used)

R1 recall flag - asking the maker or dealer whether a recall exists, a dealer or owner saying the VIN is not in a recall, or an owner crediting or blaming a recall for the event counts as yes; a recall or campaign plainly about another system does not.
R2 other cause - when a dealer, shop or other person (or an EVAP-type message) raised the cap or EVAP as the suspect and a non-EVAP cause was then found, the category is O; the owner's own unprompted cap check or a passing mention of the cap or EVAP is N.
R3 a cause cited only from a recall or bulletin text, from an owner's guess, or as "might be", with no repair or finding on this vehicle, is U (recall yes when the notice is tied to the event).
R4 (revised after the first consistency scan, applied to every batch) the category records what a shop, dealer or campaign NAMED or REPLACED; a repair that did not hold keeps its category and is flagged returned = yes. Parts swapped only by the owner on a guess, and a code reader's or parts store's text, do not count (U).
R5 returned = yes needs a statement that the same light, code or message came back or the repair did not hold; "intermittent" alone, a failed first try before the final fix, or a different failure later, is no.
R6 a light that went out by itself or was only cleared, with nothing found or done, is C.
R7 a vent valve, vent solenoid, canister vent or vent line defect that is named or plainly described is V, even when the part is integral to the tank; a vent solenoid with no EVAP link is N.
R8 a capless filler or fuel inlet problem, a filler neck, filler pipe, tank seal or tank named as the cause is F; the tank counts as the named part only when a shop or dealer named it.
R9 for N all four flags are no; flags the excerpt does not state are no.
R10 a generic fuel-system lamp or fuel smell, fuel in the canister from a pump failure, a purge valve swapped for a misfire or stall, or an inspection failure with no EVAP tie, with NO check-engine light, EVAP message or EVAP code on this vehicle, is N.
R12 a stated EVAP-leak diagnosis (small or gross EVAP leak, leak code) counts as the EVAP warning event.
R13 a code description or test line that merely names a circuit (vent circuit, purge line, fuel neck) is U unless a shop or dealer names a part as faulty or replaces it.

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POOL HISTORY
- First search (regexes above): 2,564 complaints (matches by component, overlapping: P0449/P0457 any spelling 32; vent valve wording 392; gas cap or filler neck with a warning context 966; EVAP wording with a leak/code/light context 1,265; sibling EVAP codes 301; spider campaigns 63).
- Independent completeness audit (a separate search with no access to the coding): about 3,500 narratives read outside the pool, 937 candidates that meet the unchanged relevance rule added (460 purge valve or CPV with a light or code and no "evap" word, 126 Ford P1450/P144A, about 350 cap, fuel-inlet, filler, vent-line, evaporation-wording, leak-pump or tank-collapse cases). Addendum hashed before they were coded.
- Calibration: before the first batch a random 200 (seed 20261007) was coded by two independent passes; their codes for those 200 are kept in the published file (rule_applied = calibration set).
- Final: 3,501 complaints; 2,503 relevant, 998 not relevant.