Fault code P0157 – a step-by-step guide to diagnosing and fixing it

Error code P0157 is displayed and the check engine light is on - what does this mean?

The DTC P0157 indicates that the OBD system has detected a low voltage at lambda sensor 2 in bank 2 (after the catalytic converter). This EOBD fault code indicates problems with the exhaust gas monitoring system and the oxygen sensor in the exhaust tract. The exact designation may vary for different manufacturers, but the basic function of the O2 sensor remains the same.

What causes can this error code have?

• Defective lambda sensor 2 in bank 2
• Damaged wiring to the oxygen sensor
• Corroded or loose plug connections
• Defective catalytic converter
• Exhaust gas leakage upstream of the sensor
• Faulty engine control unit (ECU)
• Dirty or clogged air filter
• Problems with the fuel supply

What symptoms occur in parallel with fault code P0157?

• Increased fuel consumption: The vehicle requires more fuel than usual due to the faulty mixture control.
• Uneven idling: The engine runs unevenly or fluctuates in speed when stationary.
• Reduced engine power: Noticeable loss of power, especially at higher engine speeds.
• Exhaust odor: Unusual smell from the exhaust due to incomplete combustion.
• Jerking when accelerating: The vehicle reacts delayed or unevenly to accelerator pedal operation.

How can the problem with fault code P0157 be rectified?

• Repairing trouble code P0157 requires a systematic approach to identify the root cause.
• Replace the lambda sensor: Replace the defective oxygen sensor 2 in bank 2 with a new OEM or high-quality aftermarket part and perform a test drive.
• Repair wiring: Check all wiring to the O2 sensor for damage, breaks or chafing and repair or replace defective wiring completely.
• Clean plug connections: Disconnect the sensor connectors, clean contacts with contact spray, check for corrosion and restore tight connections.
• Replace the catalytic converter: If the catalytic converter is defective, replace it with a new one, as a damaged catalytic converter causes incorrect readings on the downstream sensor.
• Seal the exhaust system: Locate leaks in the exhaust system upstream of the sensor using a smoke test and seal them with suitable repair pastes or replace the components.
• Check engine control unit: Have the ECU checked for software errors and have it updated or reprogrammed if necessary.