Fault code P0021 – a step-by-step guide to diagnosing and fixing it

Error code P0021 is displayed and the check engine light is on - what does this mean?

DTC P0021 is triggered by the OBD/EOBD system when a deviation is detected in the camshaft position on the intake side. This trouble code indicates a problem with the variable valve timing (VVT) or the camshaft phasing. This fault code may have slightly different names for different manufacturers, but always refers to the intake camshaft position.

What causes can this error code have?

• Defective VVT actuator (camshaft phasing unit)
• Blocked or defective VVT solenoid valve
• Contaminated or incorrect engine oil
• Defective camshaft position sensor
• Damaged timing chain or timing belt
• Loose or damaged cable connections
• Mechanical problems on the camshaft phaser
• Blocked oil ducts in the VVT system

What symptoms occur in parallel with fault code P0021?

• Loss of engine power: Noticeable reduction in engine power, especially at low engine speeds
• Uneven idling: Engine runs unevenly at idle speed
• Starting problems: Difficult to start, especially when the engine is cold
• Increased fuel consumption: Significantly higher consumption due to inefficient combustion
• Knocking noises: Metallic noises from the engine compartment
• Exhaust problems: Increased emission values during the emissions test

How can the P0021 fault code problem be rectified?

• Repairing the P0021 fault code requires a systematic approach to identify the cause.
• Change the engine oil and filter: Use the correct viscosity oil recommended by the manufacturer and replace the oil filter, as contaminated oil is often the cause of VVT problems
• Clean or replace the VVT solenoid valve: Remove the solenoid valve, clean it thoroughly with brake cleaner or replace it completely if it is defective
• Check and replace camshaft position sensor: Test the sensor with a multimeter for correct resistance values and replace it if there are any deviations
• Inspect the timing chain or timing belt: Check the tension and condition of the drive elements and replace if worn or incorrectly tensioned
• Check wiring harness and plug connections: Check all electrical connections to the VVT system for corrosion, breaks or loose contacts and repair them
• Replace VVT actuator: Replace the complete camshaft actuator if there are mechanical defects or other repairs have been unsuccessful