OBD-II Fault Code

P0312: Cylinder 12 Misfire Detected

Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P0312.

System family

Powertrain

Generic/SAE

Repair category

Engine misfire

Use this category to narrow your checks before replacing parts.

Severity

High

Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.

What P0312 usually means

Cylinder 12 Misfire Detected.

Common symptoms

Check Engine light, rough idle, hesitation, flashing MIL if severe

Likely causes

Worn spark plug; Faulty ignition coil; Injector or fuel issue; Vacuum leak; Low compression

Diagnostic checks

Scan all modules and record freeze-frame data before clearing codes; Check battery voltage and related fuses; Identify affected cylinder(s), inspect plugs/coils, check fuel trims and compression if needed

Repair guidance

Swap-test coil/injector where practical, replace worn ignition parts, repair vacuum/fuel/compression cause

Verification after repair

Clear code, road-test through the same drive condition, then rescan; Confirm misfire counters remain at zero during road test

Note: Confirm vehicle make/model/year because manufacturer-specific codes can vary. A DTC identifies a circuit or system condition, not always the failed part.