P3490Cylinder 12 Deactivation/Intake 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
- P3490 concerns the mechanical result on cylinder 12: the actuator circuit passes its electrical checks, but the cylinder does not deactivate or reactivate as intended. No manufacturer documents this code publicly; J2012 reserves the codes for cylinders 9 to 12 for engines with more than eight cylinders. In a V12 up to six cylinders can be stopped, and on a valve-switching design the commanded state depends on oil pressure reaching the switching parts; Mercedes' M137 suffered exactly there, with failures of its solenoid pack and oil pressure tubes. Lamborghini's and Bentley's twelve-cylinder engines shut whole banks and publish no valve monitoring. NHTSA's GM lifter description explains what can stick: spring-loaded locking pins moved by oil. Electrical faults on cylinder 12: P3489, P3491, P3492.
- What you may notice
- Check engine lamp on
- Misfire on cylinder 12 (P0312)
- Vibration at light load
- Likely causes
- LikelyOil pressure or quality inadequate to switch cylinder 12
- PossibleLeak in the oil supply to the cylinder 12 actuator
- PossibleLocking pins at cylinder 12 sticking
- RareActuator valve mechanically 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.