Low, dirty or degraded engine oil, or the wrong grade for the engine; Faulty or sticking camshaft phaser actuator (oil control solenoid) on bank 2; Blocked oil control valve screen or restricted oil passages to the phaser; Wiring or connector fault on the bank 2 solenoid or camshaft position sensor circuit; Worn or faulty camshaft phaser, or a stretched or jumped timing chain or belt; Faulty camshaft or crankshaft position sensor, or damaged reluctor wheel; Outdated engine control unit software where the manufacturer has issued an update for this fault.

P0021

A Camshaft Position - Timing Over-Advanced or System Performance Bank 2.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
0: AreaFuel and air metering, auxiliary emission controls
21: FaultThe specific fault in that area

What it means

P0021 is the generic code for the bank 2 intake camshaft timing being over-advanced, or the variable valve timing system not performing as commanded. The engine control unit compares the actual camshaft position, from the camshaft and crankshaft position sensors, with the target position it has requested. If the cam is further advanced than commanded, or does not follow the command within a set tolerance, the code is stored.

Symptoms

Engine warning light on
Rough or unstable idle
Reduced power or hesitation under load
Poor fuel economy
Rattling or ticking noise from the top of the engine on start-up
Occasional stalling or hard starting

Possible causes

Low, dirty or degraded engine oil, or the wrong grade for the enginelikely
Faulty or sticking camshaft phaser actuator (oil control solenoid) on bank 2likely
Blocked oil control valve screen or restricted oil passages to the phaserpossible
Wiring or connector fault on the bank 2 solenoid or camshaft position sensor circuitpossible
Worn or faulty camshaft phaser, or a stretched or jumped timing chain or beltpossible
Faulty camshaft or crankshaft position sensor, or damaged reluctor wheelrare
Outdated engine control unit software where the manufacturer has issued an update for this faultrare

How to diagnose

Read the stored codes and freeze frame data, noting engine temperature, load and speed when the fault set, and check for other timing or sensor codes
Check the engine oil level, condition and specification, and the service history
Inspect the bank 2 solenoid and camshaft sensor wiring and connectors for damage, oil contamination, corrosion or loose pins
Using live data, compare commanded and actual bank 2 camshaft position at idle and under load
Test the solenoid's resistance and its operation by commanded activation, following the manufacturer's procedure for the engine
Remove and inspect the solenoid and its filter screen for debris, sludge or sticking
Check the timing chain or belt condition and correlation between cam and crank, using live data or by inspection as the model requires
Check whether a software update or technical bulletin exists for the vehicle and engine

How to fix

Change the oil and filter to the correct specification, and correct the oil level
Replace the faulty bank 2 camshaft solenoid, or clean or replace its screen if blocked
Repair or replace damaged wiring and connectors in the solenoid or sensor circuit
Replace a faulty camshaft or crankshaft position sensor
Replace the camshaft phaser and, where worn or stretched, the timing chain or belt components
Update the engine control unit software if an update is available for this known fault

Can I keep driving?

Medium severity

Short, gentle driving is usually possible, but get it checked soon because poor oil supply or worn timing parts can cause engine damage. Avoid heavy loads and high revs, and stop if there is loud rattling or a loss of power.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.