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P0021: "A" Camshaft Position - Timing Over-Advanced or System Performance (Bank 2)
Severity: Medium Arrange diagnosis promptly and avoid heavy loads. Stop the engine for timing-chain rattle, an oil-pressure warning, severe roughness, or a flashing check engine light; towing is safer than risking a timing failure.
What does P0021 mean?
The computer requested a camshaft position but cam A on bank 2 remained too far advanced. This is an actual timing/performance problem, unlike an actuator circuit code. The phaser depends on the correct engine oil, working oil-control hardware, and properly set mechanical timing.
Generic OBD-II definition: "A" Camshaft Position - Timing Over-Advanced or System Performance (Bank 2). Confirm applicability in your vehicle service information.
Common causes
- Low, contaminated, or incorrect-viscosity engine oil
- Sticking VVT oil-control valve or cam phaser
- Incorrect belt/chain timing or worn timing components
Symptoms
- Uneven idle
- Poor acceleration
- Check engine light and reduced fuel economy
Diagnostic focus
An intake cam that remains advanced even when the command returns toward its base position points toward a sticking oil-control valve or phaser. Compare the opposite bank to separate local trouble from an oil-supply issue.
Can I keep driving with P0021?
Severity: Medium Arrange diagnosis promptly and avoid heavy loads. Stop the engine for timing-chain rattle, an oil-pressure warning, severe roughness, or a flashing check engine light; towing is safer than risking a timing failure.
If the check engine light is flashing or the car runs badly, stop driving and have it checked.
Typical fixes
- Verify oil level and the required viscosity
- Check commanded versus actual cam angle with a capable scan tool
- Test the oil-control valve and check mechanical timing if the mismatch remains
Related codes
"A" Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)P0012
"A" Camshaft Position - Timing Over-Retarded (Bank 1)P0014
"B" Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)P0015
"B" Camshaft Position - Timing Over-Retarded (Bank 1)P0020
"A" Camshaft Position Actuator Circuit (Bank 2)P0022
"A" Camshaft Position - Timing Over-Retarded (Bank 2)
Sources & review
Definitions and diagnostic background checked 2026-11-06. Generic guidance, not a substitute for the service procedure for your exact year, engine, and transmission.