P03EF: A Camshaft Profile Actuator C Control Performance/Stuck Off Bank 1

With a sliding camshaft, the intake camshaft (camshaft A) carries movable cam pieces with several lift profiles; solenoid actuators shoot a pin into a groove in the piece and shift it axially. Actuator C is the third of these actuators – not a profile position. The only known user is GM's 2.7-litre turbo four (L3B, three-step sliding cam, from model year 2019). P03EF is the function check: in the standard's wording the actuator does not do what is commanded. A Hall sensor in the actuator reports the pin position. GM uses this code for a pin that extends without being commanded (4 of 5 cylinder events, MIL on the first trip); a pin that does not extend on command shows up there through the cam piece position sensors (GM-specific codes P30BE ff). GM bulletins name swapped actuator connectors and actuators fitted to the wrong camshaft after repairs.

Medium severity. Can I keep driving?Drive little and gently. If you hear timing chain noise or the oil light comes on, shut off the engine.

Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank.

Symptoms

Check engine light on
Ticking or rattling at the camshaft carrier
Misfire, rough idle or less power in the wrong lift profile
Lift switching and cylinder deactivation out of service

Most likely causes

Actuator faulty inside: pin extends uncommanded (weak return spring)
Actuator connectors swapped, or intake and exhaust actuators fitted to the wrong camshaft
Interference in the Hall feedback signal (ground, connector)
Cam piece sticking or shift groove worn

What to check, in order

Start with the simplest. You can tick off each step.

Check the oil level and condition before anything else
Compare the reading with other engine data while varying the engine speed.
Check the solenoid valve's connector
Compare commanded and actual angles in live data
Test the solenoid valve and its filter, if it has one
Check the engine timing if there is chain noise

Good to know

Repair difficulty: medium
It can trigger limp mode.
It affects emissions.

What each character of P03EF means

P: Powertrain: engine and transmission
0: Generic code: same on every make
3: Ignition and misfires
EF: Specific fault in that system

Frequently asked questions

Can I keep driving with code P03EF?

Drive little and gently. If you hear timing chain noise or the oil light comes on, shut off the engine.

What causes code P03EF?

The most common causes are: actuator faulty inside: pin extends uncommanded (weak return spring); actuator connectors swapped, or intake and exhaust actuators fitted to the wrong camshaft; interference in the Hall feedback signal (ground, connector).

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.