Cylinder 12 Misfire Detected
The engine control module has detected a misfire in cylinder 12, meaning that cylinder is not combusting fuel properly. This causes incomplete power delivery and can damage the catalytic converter if not repaired promptly.
What You Might Notice
- Engine hesitation or stumbling during acceleration
- Rough idle or difficulty starting
- Check engine light illuminated
- Reduced engine power or performance
- Possible increase in fuel consumption
Most Common Causes
- 1
Faulty spark plug or ignition wire
Worn, fouled, or gapped spark plugs or damaged spark plug wires prevent proper ignition in cylinder 12. This is the most common cause of misfires.
- 2
Faulty ignition coil pack
A defective coil pack fails to generate sufficient voltage to fire the spark plug in cylinder 12. Coil packs commonly fail due to heat or age.
- 3
Clogged or faulty fuel injector
A fuel injector that is clogged or electrically faulty prevents proper fuel delivery to cylinder 12, causing lean misfire conditions.
- 4
Poor cylinder compression or burnt valve
Low compression in cylinder 12 due to worn piston rings, a burnt exhaust valve, or valve timing issues prevents proper combustion.
How to Diagnose It
- 1
Check Faulty spark plug or ignition wire — Worn, fouled, or gapped spark plugs or damaged spark plug wires prevent proper ignition in cylinder 12. This is the most common cause of misfires.
- 2
Check Faulty ignition coil pack — A defective coil pack fails to generate sufficient voltage to fire the spark plug in cylinder 12. Coil packs commonly fail due to heat or age.
- 3
Check Clogged or faulty fuel injector — A fuel injector that is clogged or electrically faulty prevents proper fuel delivery to cylinder 12, causing lean misfire conditions.
- 4
Check Poor cylinder compression or burnt valve — Low compression in cylinder 12 due to worn piston rings, a burnt exhaust valve, or valve timing issues prevents proper combustion.
How to Fix It
- 1
Inspect and replace spark plugs
Remove and inspect the spark plug in cylinder 12 for wear, fouling, or improper gap. Replace with OEM or equivalent specification plugs if damaged or worn.
- 2
Test and replace ignition coil
Use a multimeter to test the coil pack resistance for cylinder 12, or swap with a known-good coil to isolate the fault. Replace the faulty coil pack if resistance is out of specification.
- 3
Clean or replace fuel injector
Have the fuel injector for cylinder 12 tested and cleaned using ultrasonic cleaning equipment. If cleaning does not restore function, replace the injector with a new unit.
- 4
Perform cylinder compression test
Perform a wet and dry compression test on cylinder 12 to diagnose internal engine issues like burnt valves or worn piston rings. Compare results to manufacturer specifications and repair or rebuild as needed.
Need a deeper diagnosis?
Search for related repair guides or browse by system.