P0021: Camshaft Timing Over-Advanced (Bank 2)
The P0021 code indicates that the engine control module (ECM) has detected that the camshaft timing on bank 2 (the side opposite cylinder #1) is more advanced than the commanded value. This is typically caused by a faulty variable valve timing (VVT) solenoid, oil flow issues (low oil pressure, dirty oil, or clogged passages), or a stretched timing chain. The ECM monitors the camshaft position sensor signals to verify timing; if the actual timing deviates beyond a threshold, the code sets.
1. Most Common Causes
- Faulty or stuck VVT solenoid/actuator (phaser control valve)
- Oil control valve (OCV) clogged with sludge or mechanically failed
- Low engine oil pressure or degraded/contaminated engine oil
- Clogged VVT solenoid oil strainer/filter
- Worn, stretched, or improperly tensioned timing chain
- Mechanically damaged or excessively worn camshaft phaser gear
- Erratic or misaligned camshaft position sensor (CMP) signal
- Wiring or connector issues in the VVT solenoid circuit (short to ground, short to power, or open circuit)
- Internal PCM failure (less common)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Rough idle or engine misfire
- Reduced engine power and acceleration
- Poor fuel economy
- Engine may stall or hesitate
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Check engine oil level and condition; top up or change if necessary.
Step 3: Inspect VVT solenoid on bank 2 for debris or damage; test resistance and operation.
Step 4: Verify camshaft and crankshaft timing alignment using a scan tool or timing light.
Step 5: Check for oil pressure issues; perform a mechanical oil pressure test.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as advanced timing can cause engine knocking, overheating, or internal damage. Have it diagnosed promptly.
How much does it cost to fix?▼
Repair costs vary: replacing a VVT solenoid is $150-$300; timing chain replacement can be $500-$1500. Diagnosis typically runs $100-$150.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.