P3494Cylinder 12 Exhaust Valve Control Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P3494 is set when the exhaust valve of cylinder 12 does not follow its command although the actuator circuit is electrically intact. No manufacturer documents this code publicly; J2012 reserves the codes for cylinders 9 to 12 for engines with more than eight cylinders. Valve-based shut-off traps a charge in the cylinder; if the exhaust valve keeps opening, that cushion leaks away, which a Ford patent proposes to detect through exhaust pressure, and if it sticks shut on reactivation, compressed gas loads the valve train. The Aventador V12 and Bentley W12 sidestep this by bank shut-off without published valve switching, and for the Mercedes M137 with its hydraulic solenoid pack no public code assignment is known. Electrical faults of this actuator: P3493, P3495, P3496; intake function: P3490.
- What you may notice
- Check engine lamp on
- Jolt or knock on reactivation of cylinder 12
- Misfire on cylinder 12 (P0312)
- Likely causes
- PossibleExhaust switching element at cylinder 12 sticking
- PossibleOil pressure or quality insufficient for the exhaust switch
- RareExhaust actuator sluggish
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €3,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.