Fault code P0155 – a step-by-step guide to diagnosing and fixing it

Error code P0155 is displayed and the check engine light is on - what does this mean?

DTC P0155 is triggered by the OBD system when a defect is detected in the heater of lambda sensor 2 (bank 2). This fault code refers to the oxygen sensor located downstream of the catalytic converter, which is responsible for monitoring exhaust gas purification. The designation may vary slightly for different manufacturers, but the basic problem remains the same.

What can cause this error code?

• Defective lambda sensor 2 (bank 2)
• Blown fuse in the lambda sensor heater
• Damaged wiring to the lambda sensor
• Corroded or loose plug connections
• Defective engine control unit (ECU)
• Short circuit in the heater circuit
• Broken ground wire of the lambda sensor

What symptoms occur in parallel with fault code P0155?

• Increased fuel consumption: The vehicle consumes more fuel than usual due to inaccurate mixture control.
• Unsteady idling: The engine runs unevenly or rough at idle.
• Loss of power: Noticeable reduction in engine performance, especially when accelerating.
• Exhaust problems: Increased emission values and possible failure of the emissions test.
• Starting problems: Delayed starting of the engine, especially in cold temperatures.

How can the problem with error code P0155 be rectified?

• Repairing error code P0155 requires a systematic approach to identifying and eliminating the cause.
• Replace the lambda sensor: Replacing the defective lambda sensor 2 (bank 2) including heater with an original or high-quality replacement part, costs between 80-200 euros plus labor.
• Check and replace fuse: Check the relevant fuse in the fuse box and replace if defective, usually an inexpensive 5-10 euro repair.
• Repair wiring: Check and repair damaged wiring between ECU and lambda sensor, including insulation and soldered connections.
• Clean plug connections: Thoroughly clean corroded contacts with contact spray and ensure all connectors are firmly connected.
• Check ground wire: Check and restore the ground connection of the lambda sensor to the vehicle chassis or engine block.
• Carry out ECU diagnostics: Professional check of the engine control unit for internal defects and repair or replace if necessary.