Fault code P0156 – a step-by-step guide to diagnosing and fixing it

Error code P0156 is displayed and the check engine light is on - what does this mean?

The DTC P0156 indicates that the OBD system has detected a fault in the lambda sensor 2 (downstream oxygen sensor) of cylinder bank 2. This sensor monitors the exhaust gas values after the catalytic converter and is crucial for emission control. This EOBD code may have slightly different names for different manufacturers, but always refers to the same component.

What causes can this error code have?

• Defective lambda sensor 2 in cylinder bank 2
• Damaged or corroded cable connections to the oxygen sensor
• Loose or dirty plug connections
• Defective catalytic converter
• Exhaust gas leak upstream of the lambda sensor
• Faulty engine control unit (ECU)
• Contamination of the sensor by oil or coolant
• Electrical short circuits in the sensor circuit

What symptoms occur in parallel with fault code P0156?

• Increased fuel consumption: The vehicle requires more fuel than usual
• Uneven idling: The engine runs unevenly when stationary
• Exhaust odor: Increased or unusual odor from the exhaust
• Power loss: Reduced engine power, especially at higher engine speeds
• Failed emissions test: The vehicle does not pass the emissions test
• Jerking when accelerating: Uneven power transmission

How can the problem with error code P0156 be rectified?

• The repair requires a systematic diagnosis to identify the exact cause.
• Replacement of the defective lambda sensor 2 in cylinder bank 2 with an original part or equivalent quality component
• Repair or replace damaged cables and plug connections in the sensor circuit with subsequent insulation
• Cleaning of dirty contacts and ensuring tight connections of all electrical connections
• Catalytic converter replacement if a defect is detected, followed by system calibration
• Sealing of exhaust leaks by replacing defective seals or pipe sections
• Engine control unit update or replacement in the event of electronic faults according to manufacturer specifications