Camshaft Timing Over-Advanced or System Performance (Bank 2)
P0021 indicates that the Engine Control Module (ECM) has detected that the camshaft timing on Bank 2 (the side opposite cylinder #1) is over-advanced or the variable valve timing (VVT) system is not performing within specifications. This can be caused by a faulty VVT solenoid, oil flow issues (low oil pressure, dirty oil, or clogged passages), a stretched timing chain, or a defective camshaft phaser. The ECM compares actual camshaft position to desired position and sets this code when the deviation exceeds a threshold.
01. Most Common Causes
- Faulty VVT solenoid on Bank 2
- Low engine oil level or pressure
- Contaminated or degraded engine oil
- Clogged oil passages to the VVT phaser
- Stretched or slipped timing chain/belt
- Defective camshaft phaser/actuator
02. 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
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data. Check for additional codes like P0010-P0014 or P0020-P0024.
Step 2: Inspect engine oil level and condition. Low or dirty oil is a common cause.
Step 3: Test the Bank 2 VVT solenoid resistance and operation using a multimeter and scan tool.
Step 4: Perform a mechanical timing check to verify timing chain/belt alignment.
Step 5: Check oil pressure at the VVT solenoid port; low pressure indicates oil pump or passage issues.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances. Over-advanced timing can cause engine knocking, overheating, or internal damage. Have it diagnosed promptly.
How much does it cost to fix?▼
Costs vary: VVT solenoid replacement $150-$300; oil change and cleaning $50-$100; timing chain repair $500-$1500. Average diagnostic fee $100-$150.