Powertrain, shared range

P3490 Cylinder 12 Deactivation/Intake Valve Control Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Oil pressure or quality inadequate to switch cylinder 12
Leak in the oil supply to the cylinder 12 actuator
Locking pins at cylinder 12 sticking
Actuator valve mechanically sluggish

Symptoms

  • Check engine lamp on
  • Misfire on cylinder 12 (P0312)
  • Vibration at light load

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–3,500
Time0–12 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

cylinder deactivation solenoidlifterengine oil

Related codes

P3489P3491P3492P3494P0312P3497

References: law.cornell.edu, en.wikipedia.org, en.wikipedia.org, static.nhtsa.gov.