Fault code P0025 – a step-by-step guide to diagnosing and fixing it

Error code P0025 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system uses DTC P0025 to detect a malfunction in the camshaft phasing on the exhaust side (bank 2). This trouble code indicates problems with the variable valve timing system, which is responsible for optimum engine performance and emission control.

What can cause this trouble code?

• Defective camshaft phaser (VVT actuator)
• Clogged or defective solenoid valve for the camshaft phasing unit
• Contaminated or incorrect engine oil
• Oil pressure in the system too low
• Damaged or stretched timing chain
• Defective camshaft position sensor
• Loose or corroded plug connections
• Blocked oil ducts in the cylinder head
• Defective engine control unit (ECU)

What symptoms occur in parallel with fault code P0025?

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

How can the problem with fault code P0025 be rectified?

• Repairing fault code P0025 requires a systematic approach to identify the exact cause.
• Carry out a complete oil change with the viscosity specified by the manufacturer and replace the oil filter, as contaminated oil is often the main cause
• Remove the solenoid valve of the camshaft phasing unit, clean thoroughly or replace completely if defective
• Check the camshaft phasing unit (VVT actuator) for mechanical damage and replace if worn or blocked
• Check timing chain and chain tensioner for correct tension and wear, replace if necessary
• Test the camshaft position sensor and replace if the signal values are incorrect
• Check all electrical connections and wiring harnesses for corrosion or damage and repair them
• Diagnose oil pressure system and repair oil pump or clogged lines if pressure is low
• Check engine control unit for software errors and update firmware if necessary