P03EF
A Camshaft Profile Actuator C Control Performance/Stuck Off (Bank 1)
Cam profile actuator A position C is electrically OK but does not engage when commanded. The cam phaser actuator adjusts intake/exhaust timing under load — a stuck or slow phaser kills mid-rpm torque and can throw correlation codes between cam and crank.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
Symptoms
- Check engine light on
- Power loss especially in mid-rpm range
- Possible rough idle or stalling
- Increased fuel consumption
Common causes
Ordered by how often each turns out to be the cause.
- Lock pin or oil supply restrictedCommon
- Carbon or debris buildup preventing free movementLess likely
- Component wear with age - mechanical playLess likely
Parts involved
- Camshaft Position Actuator
P03EF is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.