# Sorting rules - cylinder 6 / cylinder 5 misfire complaints (P0306 / P0305 study)

Written before any complaint in the set was sorted.

## 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). A complaint is in the pool if its narrative matches either of the following case-insensitive text searches:

1. R1 - the code by any spelling (letter O for zero, a space, hyphen or period after the P, suffix 00): P0305 or P0306, or a bare number after a code word:
   `(?<![A-Z0-9])P\s?[-.]?\s?[0O]\s?3\s?[0O]\s?[56](?:\s?[-:]?\s?[0O]{2})?(?![0-9])`
   `\b(?:code|codes|dtc|dtcs|error|cel|coded|fault)\W{0,6}#?\s?[0O]?30[56]\b`
2. R2 - cylinder 5 or 6 named in owners' words (cylinder 5, cyl #6, 5th cylinder, number six cylinder, no. 5 cylinder ...) together with a misfire word (misfire, mis-fire, missing, misses, firing):
   `(?:(?:cyl(?:inder)?|cly?n?d?r?|cyl\.)\s*(?:#|no\.?|number|num)?\s*[-:]?\s*(?:5|6|five|six|fifth|sixth)\b)|(?:\b(?:5th|6th|fifth|sixth)\s+cyl)|(?:#\s?[56]\s+cyl)|(?:\b[56]\s*(?:cylinder|cyl)\b)`
   with `misfir|mis-fir|miss(?:es|ing|ed)\b|fir(?:e|ing|es)\b` somewhere in the same narrative.

Background for the reader (not a sorting rule): P0305 means "cylinder 5 misfire detected" and P0306 means "cylinder 6
misfire detected". Cylinder numbers 5 and 6 exist on V6, V8 and straight-six engines (not on four-cylinder engines);
the number is a position in the maker's firing-order numbering and differs by maker and by engine. P0300 is the general
"random/multiple cylinder misfire" code and P0301-P0304, P0307, P0308 are the single-cylinder codes for the other
positions; they are treated in separate PulsCar articles. Owners say "cylinder 6 misfire", "misfire on 6", "number 5
cylinder", "5th cylinder".

For each complaint record exactly one CATEGORY, one CYL value and five 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 a cylinder-5 or cylinder-6 misfire event on THIS vehicle. Use N when:
    - the match is false (cylinder 5/6 appears in a different context: 5th gear, "5 cylinder" engine size, "6 cylinder
      engine" as a model description, a coil code for another cylinder such as P0355/P0356 with no misfire, an exhaust
      manifold bolt, a valve seat with no misfire statement);
    - the narrative only lists the code/words among many complaints with no statement that this vehicle had a cylinder 5
      or 6 misfire, warning, code, symptom or repair;
    - the words come from another vehicle, a news story or advice, not this vehicle;
    - only other cylinders are named (P0301, P0302 ... P0304, P0307, P0308) or only the general P0300, and cylinder 5 or 6
      is not named for this vehicle;
    - a mention of cylinder 5/6 comes only from a damage description with no misfire (e.g. a bearing, a bolt).
    NOT N (relevant) when, on this vehicle: P0305 or P0306 is named; OR a misfire (or missing/not firing) is stated for
    cylinder 5 or 6 (or both with others); OR cylinder 5/6 is stated to be the cylinder with the failed part that caused a
    misfire.

## CYL (which cylinder the complaint names, one value)
5 - cylinder 5 only (P0305 or words).   6 - cylinder 6 only (P0306 or words).   B - both 5 and 6 named, or 5 or 6 named
together with other cylinders as misfiring.   X - relevant to the pool but no specific number is stated (rare for pool
members; also for N rows put X).   For N rows always put X.

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

C - Ignition coil. A coil, coil pack or coil boot/connector on the cylinder was named by a shop, dealer or mechanic as
    the cause, or was replaced and that is the repair stated.
P - Spark plug. A spark plug (worn, fouled, wrong gap, cracked, oil in the plug well/tube) was named as the cause or was
    replaced and that is the repair stated.
I - Fuel injector. An injector was named as the cause, cleaned or replaced.
V - Valvetrain. Lifter, rocker arm, camshaft, pushrod, valve (burnt, bent, stuck), valve spring, cylinder-deactivation
    lifter/AFM/DOD/MDS component, or cam follower was named as the cause or replaced.
H - Head gasket or coolant in the cylinder. A head gasket, warped/cracked head or block, coolant or hydro-lock in the cylinder was named.
E - Engine failure, other. The engine was named as failed, damaged, seized, with low compression, a bad piston/ring/bore/
    bearing/crank, or was replaced/rebuilt/quoted for replacement, and no more specific category V or H is named.
F - Software or campaign only. A reflash/recalibration, recall, TSB, special-coverage, extended warranty or maker
    program was the only repair stated (no part named as cause).
O - Another cause. A cause outside C P I V H E was named (vacuum/intake leak, fuel quality or pump, wiring/harness/
    connector, sensor, carbon build-up, oil consumption, EGR, exhaust, ECM, transmission, hybrid system) or the misfire
    was traced to something else.
K - 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; also an owner's own guess, a forum, a code reader or scan with no shop/dealer/mechanic named; also parts replaced
    by the owner/shop that did not fix it with no later cause named.

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. Most specific
mechanical cause first: H, V, then E (E only when no H or V is named); then C, P, I. If several parts were replaced
together and no single one is named as the cause, use C if coils were replaced, otherwise P, otherwise I. Among F, O, K,
U: F before O before K before U. A cause the owner merely guesses at ("probably the coil") does not count unless a
shop or dealer said it or the part was replaced by someone.

## FLAGS (yes/no)

stall - the complaint states that while driving or at a stop the engine stalled, shut off, lost power, went into
    limp/reduced power, or lost power or shook badly because of this fault.
flash - the complaint states the check-engine light was flashing or blinking.
engine - the complaint states an engine replacement, rebuild, new long block or major internal engine repair was done,
    quoted or told to be required.
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.
returned - the complaint states that after a repair or a reset the same light, code or symptom came back, or the repair
    did not fix it.

## OUTPUT

One CSV line per complaint, in the order given, no header line:
`odino,category,cyl,stall,flash,engine,recall,returned,note`
category is one letter (N C P I V H E F O K U); cyl is one of 5 6 B X; flags are yes or no (for N, cyl is X and all five
flags are no); note is at most 15 words, no commas, saying what decided the category.


## FINGERPRINT
The text above was written and dated before any complaint was sorted. Date (UTC) and fingerprint of the file:
2026-10-14T08:25:32Z
27553430dcb34390268abbc809997049213d4d32e2d117e0a35b05c317f6edbe  codebook.md

## RULES USED TO SETTLE DISAGREEMENTS (written after the first sortings, applied to every disagreement)
R1 parts replaced that the owner says did not fix it, with no cause named by a shop or dealer -> U (returned=yes).
R2 the final repair that fixed it (or the cause the shop named last) decides the category; an owner's own guess (likely, suspected, seems) does not count -> U.
R3 engine failure is E only when no head or valvetrain cause is named; a cylinder head that had to be shaved/machined/replaced is H; lifters, cam, rocker, valve spring are V.
R4 cyl = B when 5 or 6 is named together with another cylinder as misfiring (any codes P0305/P0306 together, or 5/6 with 3, 4, 7 ...); 5 or 6 when only that one is named. A code list that contains P0306 but says "cylinder 6" in words is 6.
R5 N when the narrative states a part failure on cylinder 5 or 6 but no misfire anywhere in it (rod bearing with no misfire stated).
R6 stall = yes only when the narrative says stalled, shut off, died, lost power, limp mode, would not accelerate or engine stopped; shaking, shuddering, jerking, sputtering or rough running alone is not stall.
R7 engine = yes when the narrative says the engine was replaced, rebuilt, taken apart, or that camshaft, lifters or cylinder heads were replaced/machined, or such repair was quoted or told to be required; a part named as the cause with no repair statement is no.
R8 recall = yes also when the dealer calls it a known problem, or the owner cites a bulletin or recall number, or says no recall exists/should exist for it.
R9 returned = yes only when the same light, code or symptom came back after a repair or reset, or parts replaced did not fix it.
R10 flash = flashing check-engine light only; a flashing stability/traction light is not flash.
R11 codes cleared by a service department with nothing else done -> K.
R12 a timing chain, phaser or CVVT fault is O (another cause), not V.

## HOW THE SET GREW
First search: 426 complaints (the two text searches above), sorted twice. Second search: an independent search of the same file for what the first one missed (other spellings, cylinder wording, part-fault wording); 175 complaints were added, 170 of them relevant, and sorted twice by the same unchanged rules. In the complaints file, found_by says which search found each complaint. Category letters: N not relevant; C ignition coil; P spark plug; I fuel injector; V valvetrain (lifter, rocker, camshaft, valve); H head gasket or coolant in the cylinder; E engine failure or replacement, other; F software or a program only; O another cause; K checked and cleared; U nothing found or done yet, or parts that did not help.