Fault code P0033 – a step-by-step guide to diagnosing and fixing it

Error code P0033 is displayed and the check engine light is on - what does this mean?

The OBD system detects a fault in the turbocharger bypass valve control circuit when DTC P0033 is stored. This trouble code indicates that the control unit has detected a problem with the electrical supply or the signal of the turbocharger bypass valve. For various manufacturers, this fault code may also be referred to as "Turbocharger Bypass Valve Control Circuit".

What causes can this fault code have?

• Defective turbocharger bypass valve
• Damaged wiring to the bypass valve
• Corroded or loose plug connections
• Defective engine control unit (ECU)
• Short circuit in the control line
• Interrupted ground connection
• Faulty power supply to the valve
• Mechanical blockage of the bypass valve

What symptoms occur in parallel with fault code P0033?

• Loss of power: The engine develops less power, especially at higher engine speeds
• Poor acceleration: The vehicle reacts sluggishly when accelerating
• Uneven idling: The engine runs unevenly at idle speed
• Increased fuel consumption: Consumption increases noticeably
• Whistling noises: Unusual noises from the engine compartment
• Black smoke: Dark exhaust fumes when accelerating
• Check engine light: The warning light is permanently illuminated

How to fix the problem of error code P0033?

• The repair requires a systematic approach to identify the exact source of the fault.
• Complete replacement of the turbocharger bypass valve including seals and fastening material, followed by a test drive to check the function
• Replacement of the entire wiring from the control unit to the bypass valve with OEM-specified cables and professional insulation of all connection points
• Cleaning and renewal of all electrical contacts on the bypass valve connector with contact spray and subsequent application of corrosion protection
• Replacement of the engine control unit after prior diagnosis with professional diagnostic equipment and subsequent programming to vehicle-specific parameters
• Mechanical cleaning of the bypass valve mechanism with special cleaning agents and checking the mobility of all mechanical components
• Complete check and repair of the power supply including fuses, relays and ground connections in the entire turbocharger control circuit