Fault code P0029 – a step-by-step guide to diagnosing and fixing it

Error code P0029 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has detected a fault in the exhaust valve control circuit A, which indicates a problem with the variable valve timing. This DTC P0029 mainly affects the exhaust valve control system and can occur with different manufacturers, although the exact designation may vary slightly.

What causes can this error code have?

• Defective exhaust valve control valve (VVT valve)
• Dirty or clogged oil control valve
• Low engine oil level or low-quality engine oil
• Damaged wiring to the VVT control valve
• Corroded or loose plug connections
• Defective camshaft sensor
• Mechanical problems on the camshaft phasing unit
• Blocked oil ducts in the cylinder head
• Faulty engine control unit (ECU)

What symptoms occur in parallel with fault code P0029?

• Starting problems: The vehicle is difficult to start or starts irregularly
• Idling problems: Unsteady or fluctuating idling
• Power loss: Reduced engine power, especially at low engine speeds
• Increased fuel consumption: Significantly higher fuel consumption than usual
• Engine knocking: Knocking noises from the engine compartment, especially when accelerating
• Exhaust problems: Increased exhaust emissions and possible failure of the emissions test

How can the problem with error code P0029 be rectified?

• Repairing this trouble code requires a systematic approach to identify the exact cause.
• Check and change the engine oil: Check the oil level and fill with high-quality engine oil of the correct viscosity, as contaminated or low-quality oil is the most common cause
• Replace VVT control valve: Remove the defective exhaust valve control valve and replace it with a new original part, replacing the seals in the process
• Check electrical connections: Check all cables and connectors to the VVT system for damage, corrosion or loose connections and repair them
• Replace camshaft sensor: If the sensor is defective, remove it and replace it with a new one, ensuring correct alignment
• Clean the oil ducts: Clear blocked oil passages in the cylinder head by professional engine flushing or mechanical cleaning
• Reprogram the engine control unit: After repairs, reset the ECU and have it reprogrammed if necessary