P0021
A Camshaft Position - Timing Over-Advanced or System Performance (Bank 2)
When a vehicle powertrain module registers the fault code P0021, it points directly to an internal system malfunction identified as "A Camshaft Position - Timing Over-Advanced or System Performance (Bank 2)". Operating your engine under this condition may degrade long-term fuel maps.
Driver's Summary
Storing code P0021 is your car's way of telling you something is wrong with the a camshaft position - timing over-advanced or system performance (bank 2). Typical symptoms include engine stalling, hard starting, rattling noise from the engine. The vehicle is usually drivable, but the root cause needs attention soon to avoid more expensive repairs down the road.
Symptoms
Engine stalling, hard starting, rattling noise from the engine
Common Causes
- Faulty VVT control solenoid on Bank 2
- Clogged engine oil passages
- Worn timing chain
- Defective camshaft phaser
How to Fix
- 1 Replace Bank 2 VVT solenoid
- 2 Perform oil and filter change
- 3 Clean oil control valve filter
- 4 Replace camshaft phaser sprocket
Technical Explanation
Code P0021 is confirmed when the ECM's diagnostic algorithm detects a parameter deviation that persists across a defined number of consecutive drive cycles. The diagnostic runs during closed-loop operation only, ensuring the engine is at full operating temperature and the PCM's fuel trim feedback loop is active before confirming any out-of-range condition. The fault remains stored in memory even after the MIL is cleared; it becomes a confirmed DTC after failing two consecutive drive cycles, and the PCM logs a freeze frame record of the engine's exact operating state at the moment of detection.
Is It Safe to Drive?
You can drive short distances, but the symptoms — engine stalling, hard starting, rattling noise from the engine — indicate the affected system is compromised. Leaving this unresolved will lead to progressively worse fuel economy and potential damage to components beyond the original fault.
Mechanic's Pro Tip
With P0021, always change the engine oil with the correct factory viscosity as the absolute first step before any electrical testing — dirty or wrong-viscosity oil prevents VVT actuators from responding properly regardless of solenoid condition. After the oil change, warm the engine fully and monitor camshaft advance angle live on a scan tool; if it still won't advance to the commanded target, then test the VVT solenoid. Cleaning the solenoid's internal filter screen (often packed with sludge) resolves a large percentage of these codes without replacing the solenoid.
VVT Solenoid: $150 - $300; Phaser: $400 - $1,200