Fault code P0154 – a step-by-step guide to diagnosing and fixing it

Error code P0154 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has detected that lambda sensor 1 in bank 2 (the cylinder bank opposite cylinder 1) is showing no activity or is not responding properly. This DTC P0154 affects the oxygen sensor before the catalytic converter and can occur with different manufacturers, whereby the exact position can vary depending on the engine design.

What causes can this error code have?

• Defective lambda sensor 1 bank 2
• Damaged or corroded cable connections to the lambda sensor
• Interrupted heating circuit of the oxygen sensor
• Defective fuse for the lambda sensor heater
• Dirty or oily lambda sensor
• Faulty engine control unit (ECU)
• Vacuum leak in the intake tract
• Defective ground wire of the lambda sensor
• Short circuit in the wiring

What symptoms occur in parallel with fault code P0154?

• Increased fuel consumption: The vehicle consumes significantly more fuel than usual because the mixture control is not functioning optimally.
• Uneven idling: The engine runs unevenly at idle or fluctuates in speed.
• Loss of power: Noticeable reduction in engine power, especially when accelerating.
• Black smoke: Dark exhaust fumes due to an excessively rich fuel/air mixture.
• Starting problems: Difficult engine starts, especially when the engine is cold.

How can the problem with fault code P0154 be rectified?

• Repairing fault code P0154 requires a systematic approach to identify the exact cause.
• Replace the lambda sensor: Replace the faulty oxygen sensor bank 2 sensor 1 with an original part or high quality replacement part, including correct calibration via the diagnostic tool.
• Repair wiring: Check and repair all wiring connections to the oxygen sensor, replace damaged wiring and ensure proper ground connection.
• Check the lambda sensor heater fuse: Check the corresponding fuse in the fuse box and replace it if necessary, then check the heater function with a multimeter.
• ECU reset and reprogramming: Carry out a complete reset of the engine control unit and reprogram the lambda sensor values to ensure that the system recognizes the new sensor correctly.
• Check intake tract for leaks: Locate and fix vacuum leaks in the intake system, as these can affect the lambda sensor response, and replace defective hoses or gaskets.