P3490 code meaning
Cylinder 12 Deactivation/Intake Valve Control Performance
Powertrain system Generic code P34xx codes Check engine light
What P3490 means
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.
P3490 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyHard
- Typical labor0.5 to 12 hours
- Clears after repairAfter a drive cycle
Symptoms of P3490
- Check engine lamp on
- Misfire on cylinder 12 (P0312)
- Vibration at light load
Common causes of P3490
- Most 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
- Less likelyActuator valve mechanically sluggish
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Cylinder deactivation solenoidLifterEngine oil
What each part of P3490 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 3 | Mixed range: generic and manufacturer-specific codes. |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 90 | The exact fault in that area. |
What to do next
- Note P3490 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P3490
What does P3490 mean?
P3490 means "Cylinder 12 Deactivation/Intake Valve Control Performance". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P3490?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P3490 fail an emissions test?
Yes, it can. P3490 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P3490 to fix?
Difficulty: hard. A typical repair takes 0.5 to 12 hours of work. This is a job for a workshop.
Will P3490 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.