Fault code P0235 – a step-by-step guide to diagnosing and fixing it

Error code P0235 is displayed and the check engine light is on - what does this mean?

DTC P0235 is triggered by the OBD system when a problem is detected with the turbocharger boost pressure control circuit "A". This fault code indicates that the boost pressure is outside the parameters expected by the engine control unit. For various manufacturers, this code may also be referred to as "Turbocharger Boost Control A Circuit".

What causes can this error code have?

• Defective wastegate valve or wastegate actuator
• Damaged or blocked vacuum hoses to the turbocharger
• Defective boost pressure sensor (MAP sensor)
• Leak in the intake tract or intercooler
• Dirty or defective mass air flow sensor
• Defective turbocharger control unit
• Mechanical damage to the turbocharger itself
• Clogged air filter
• Loose or corroded plug connections
• Defective engine control unit

What symptoms occur in parallel with fault code P0235?

• Loss of power: Significantly reduced engine power, especially when accelerating
• Unusual noises: Whistling or hissing noises from the engine compartment
• Black smoke: Dark exhaust emissions, especially under load
• Poor acceleration: Delayed response when accelerating
• Increased fuel consumption: Noticeably higher consumption than usual
• Engine knocking: Irregular combustion noises
• Emergency running program: Engine runs in safety mode with limited power

How to fix trouble code P0235?

• Repairing trouble code P0235 requires a systematic approach to identify the cause.
• Replacing the defective wastegate actuator and checking the vacuum supply, including all hoses and connections to the turbocharger system
• Replacement of all vacuum hoses and connections to the turbocharger if cracks, leaks or hardening are detected
• Replacement of the boost pressure sensor (MAP sensor) after prior inspection of the electrical connections and power supply
• Repair or replacement of the charge air cooler if leaks are detected, including all connecting hoses
• Cleaning or replacement of the mass air flow sensor and simultaneous replacement of the air filter for optimum air supply
• Replacement of the turbocharger unit in the event of mechanical damage or irreparable defects to the compressor or turbine
• Checking and repairing all electrical connections, plugs and cable connections in the turbocharger control circuit
• Complete diagnosis and, if necessary, replacement of the engine control unit in the event of software errors or hardware defects