Fault code P0056 – a step-by-step guide to diagnosing and fixing it

Error code P0056 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has detected a fault in the heating circuit of lambda sensor 2 (bank 2). This DTC P0056 indicates problems with the heating of the downstream oxygen sensor, which is important for the proper functioning of the catalytic converter. With various manufacturers, this trouble code can also be referred to as "O2 Sensor Heater Circuit Malfunction".

What causes can this error code have?

• Defective lambda sensor 2 (bank 2)
• Damaged or corroded cable to the oxygen sensor
• Loose or corroded plug connections
• Faulty fuse in the heating circuit of the lambda sensor
• Faulty engine control unit (ECU)
• Short circuit or interruption in the wiring
• Defective relay for the sensor heater

What symptoms occur in parallel with fault code P0056?

• Increased fuel consumption: The vehicle consumes more fuel than usual because the mixture control is impaired.
• Poor engine performance: The engine runs unevenly or has less power, especially when starting cold.
• Exhaust problems: Increased emission values and possible failure of the emissions test.
• Jerking when idling: The engine runs unevenly or stutters when idling.
• Delayed response: The vehicle reacts sluggishly to accelerator pedal operation.

How can the problem with fault code P0056 be rectified?

• Repairing fault code P0056 requires a systematic approach to identify and rectify the cause.
• Replace lambda sensor 2 (bank 2) completely: Replace the defective oxygen sensor with a new original part or high-quality spare part and reprogram the control unit.
• Check and repair wiring and plug connections: Check all cables to the oxygen sensor for damage, corrosion or loose connections and replace defective cables completely.
• Replace the fuse and relay of the sensor heating circuit: Check the corresponding fuse in the fuse box and the relay for the lambda sensor heating and replace defective components.
• Diagnose the engine control unit and replace if necessary: Have the ECU checked for defects by a specialist and repaired or replaced if necessary.
• Carry out a complete electrical diagnosis: Use a professional diagnostic device to measure the voltage values and resistances in the entire heating circuit of the lambda sensor.