P0312
Cylinder 12 Misfire Detected
Encountering the engine check light code P0312 signifies an explicit mechanical or electrical operational breakdown categorized as "Cylinder 12 Misfire Detected". Professional scanner tools usually flag this subsystem loop early on.
Driver's Summary
A P0312 fault code points directly to a problem with cylinder 12 misfire detected that the ECM has confirmed over multiple drive cycles. Typical symptoms include noticeable power loss, engine vibration, check engine light. This condition is classified as high severity. Prompt diagnosis is essential to prevent cascading damage to related components.
Symptoms
Noticeable power loss, engine vibration, check engine light
Common Causes
- Faulty ignition coil or spark plug
- Clogged fuel injector
- Carbon buildup on intake valves
- Internal engine damage
How to Fix
- 1 Replace coil and spark plug
- 2 Clean or replace fuel injector
- 3 Perform intake valve cleaning
- 4 Test engine compression
Technical Explanation
Code P0312 is confirmed when the ECM's diagnostic algorithm detects a parameter deviation that persists across a defined number of consecutive drive cycles. For injector-specific codes, the ECM monitors the injector control circuit voltage drop during each pulse; a shorted or open injector presents a characteristic resistance signature that differs measurably from a healthy unit. The MIL illuminates after the fault is confirmed on two consecutive drive cycles, and the freeze frame data captured at first detection is stored in the PCM's memory for diagnostic reference.
Is It Safe to Drive?
With P0312 active, your engine or transmission is not operating within design parameters. Short-term driving may seem fine, but internal damage is accumulating — particularly to faulty ignition coil or spark plug.
Mechanic's Pro Tip
The fastest isolation technique for P0312 is the coil swap test: move the ignition coil from the affected cylinder to a neighboring cylinder and clear the code. If the misfire follows the coil, it's the coil. If it stays on the same cylinder, focus on the spark plug, injector, or compression. Never replace coils without also replacing the spark plug in that cylinder — a fouled plug will kill a new coil within weeks.
Ignition repair: 150 - 400; Engine work: 1,500+