Cylinder 12 Exhaust Valve Control Performance

Possible causes

• CommonFailed or collapsed deactivation lifter on cylinder 12
• CommonLow, old or wrong-viscosity engine oil
• CommonBlocked oil passage to the cylinder 12 lifter
• CommonWeak or sticking control solenoid
• PossibleLow oil pressure from a worn pump or clogged pickup screen
• PossibleWorn camshaft lobe for cylinder 12

What you might notice

• Misfire on cylinder 12
• Ticking or tapping from the top of the engine
• Shudder as the system switches in and out
• Reduced power
• Check engine light on, sometimes flashing

What to check, in order

1. Check the oil level, condition and viscosity first. A hydraulically actuated lifter cannot work on oil that is low, degraded or too thick, and this is the most common cause by a wide margin.
2. Listen for a tick from the top of the engine. A persistent tick alongside this code points firmly at the cylinder 12 lifter rather than the solenoid.
3. Read all codes. A misfire code for cylinder 12 alongside this one supports a mechanical fault.
4. Check oil pressure against specification.
5. Do not keep driving on a persistent misfire. Unburnt fuel reaching the catalytic converter destroys it, and a collapsing lifter can wear the camshaft lobe - either one turns this into a far more expensive repair.
6. If the engine has done high mileage on extended oil changes, expect the repair to involve lifters rather than a solenoid, and get a proper assessment before spending on parts.