What does the P0021 fault code mean?
The P0021 fault code, applicable to all car manufacturers, means “A Camshaft Position – Timing Over-Advanced or System Performance (Bank 2)“.
Background Information: The camshaft controls the opening and closing of the valves. In a variable valve timing system, the electronic camshaft adjusting valve (or oil control valve, OCV) adjusts the camshaft angle by changing the oil pressure to the camshaft adjuster (mechanical) according to instructions from the engine control module (ECM), ensuring the valves open and close at the optimal time. Causes of the P0021 fault include incorrect timing of the intake/left/front camshaft, mechanical jamming of the camshaft due to over-timing, or the actuator valve being stuck in the open position. In short, it’s either timing too early or system performance issues. “A” camshaft must refer to the “intake,” “left,” or “front” camshaft. Determine left/right and front/rear from the driver’s position with a forward view. The first group refers to the bank of cylinders including cylinder 1, and the second group is the group opposite the first group.
Symptoms of P0021 Error Code
- Loss of engine power
- Engine instability
- Increased fuel consumption
- Difficulty starting the engine or prolonged starting time
- “Check Engine” light illuminates
- Engine makes metallic knocking sounds or noises
Main Causes of P0021 Error Code
- Low or dirty engine oil
- Faulty variable valve timing (VVT) solenoid
- Worn or stretched timing chain
- Faulty camshaft position sensor
- Interrupted electrical connection in the VVT system
- Mechanical problems in the valve train
P0021 Error Code in Different Vehicles
P0021 in Nissan: It is most common in Altima, Murano, and Maxima models. The most common cause is a faulty VVT solenoid or contaminated old engine oil.
P0021 in Subaru: Popular in Legacy and Outback models. It is usually associated with abnormal operation of the phase shifter and is sensitive to oil quality.
P0021 in Infiniti: Affects G35, G37, and FX35 models. The error may be caused by timing synchronization violations or wiring problems.
P0021 in Mazda: It appears on Mazda 6 and CX-7 models. The cause may be a sensor malfunction or contamination of the VVT system.
P0021 in BMW: Most likely to occur in models equipped with the VANOS system. This error occurs when components are worn or the oil quality is poor.
How to Diagnose P0021 Error Code?
Step 1: Read the error code with an OBD2 scanner.
Step 2: Check the engine oil level and condition.
Step 3: Perform a visual inspection of the VVT solenoid and connectors.
Step 4: Check the camshaft position sensor.
Step 5: Analyze the ignition timing and perform a mechanical inspection if necessary.
| Possible Causes | How to Check？ |
|---|---|
| Low or dirty oil level | Check engine oil level and condition |
| Faulty VVT solenoid valve | Test power supply and resistance |
| Timing chain failure | Check tension and wear marks |
| Defective camshaft position sensor | Check sensor signal with an OBD scanner |
| Damaged wiring or connector | Visual inspection and continuity check |
Tools needed: OBD2 diagnostic scanner, multimeter, mechanical oil pressure gauge, engine disassembly tool kit
How to fix P0021 error code? (Solutions to the problem)
Simple fixes
- Engine oil and filter replacement
- Clean or replace VVT solenoid valve
- Clean connectors and check power supply
In-depth diagnostic and repair solutions
- Replace stretched timing chain
- Replace faulty camshaft position sensor
- Restore phase shifter hydraulic system
- Comprehensive diagnosis of engine ECU
Troubleshooting by symptoms
| Symptom | Possible solution |
|---|---|
| Power loss | Check phase shifter and engine oil |
| Increased fuel consumption | Diagnosis of VVT and ignition system |
| Difficulty starting the engine | Check camshaft sensor and timing chain |
| Engine noise | Check mechanical components of the timing system |
P0021 Error Frequently Asked Questions
Can you drive a car with a P0021 error?
Not recommended. Error P0021 can lead to serious mechanical damage to the engine, including timing chain stretching and incorrect valve timing.
Can the P0021 error be caused by oil?
Yes, low or dirty oil is one of the most common causes of this error. Engine oil affects the operation of the phase shifter and VVT solenoid valve.
How to reset the P0021 error code without a scanner?
You can disconnect the battery for 10-15 minutes, but if the fault is not resolved, the error will reappear after the next engine start.
The P0021 error disappeared on its own. Do I need to do anything?
Even if the error disappears, a diagnosis is recommended. It may disappear temporarily, but the underlying cause may still exist and could lead to more serious problems in the future.
Can I replace the VVT solenoid valve myself?
Yes, if you have basic skills and tools. However, be sure to follow the instructions carefully and avoid damaging the connector or the valve itself.
Related OBD2 Errors:
P0011 – A Camshaft Position – Timing Over-Advanced or System Performance (Bank 1)
P0022 – A Camshaft Position – Timing Over-Retarded (Bank 2)
P0340 – Camshaft Position Sensor A Circuit (Bank 1 or Single Sensor)
Important! If the P0021 error is accompanied by unusual noises from the engine compartment, this could be a sign of severe wear on the camshaft or timing chain. Driving the vehicle in this condition is highly inadvisable. Pay attention to the quality and level of the engine oil and change it regularly, especially if your vehicle uses a VVT system. If an error occurs, it should be diagnosed as soon as possible to avoid serious consequences.