Fault code P0051 – a step-by-step guide to diagnosing and fixing it

Error code P0051 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 1 (sensor after the catalytic converter). This DTC P0051 indicates a low resistance or short circuit in the heating element circuit. The exact designation may vary slightly for different manufacturers, but the basic problem remains the same.

What can cause this error code?

• Defective heating element of lambda sensor 2 bank 1
• Damaged or corroded cable to the lambda sensor
• Loose or corroded plug connections
• Short circuit in the wiring to the lambda sensor
• Defective fuse in the lambda sensor heating circuit
• Faulty engine control unit (ECM/PCM)
• Short circuit to earth in the heating circuit wiring

What symptoms occur in parallel with fault code P0051?

• Increased fuel consumption: The vehicle consumes more fuel than usual because the lambda sensor is not working optimally.
• Poor exhaust values: The emissions deteriorate significantly, which can lead to problems at the next general inspection.
• Uneven idling: The engine runs unevenly or jerks noticeably when idling.
• Reduced engine power: A loss of power is particularly noticeable when the engine is cold.
• Extended warm-up phase: The engine takes longer to reach its optimum operating temperature.

How can the problem with error code P0051 be rectified?

• The repair requires a systematic approach to identify the exact source of the fault.
• Replace lambda sensor 2 bank 1 completely: Replace the defective sensor including heating element with a new original part or high-quality spare part, as the internal heating element is usually irreparably damaged.
• Check and repair wiring and plug connections: Check all cables to the lambda sensor for damage, corrosion or loose connections and repair or replace defective cables completely.
• Check and replace the fuse in the heating circuit: Locate the corresponding fuse for the lambda sensor heating circuit in the fuse box and replace it with a new one of identical amperage if necessary.
• Diagnose the engine control unit and replace if necessary: Have the ECM/PCM professionally tested, as an internal fault can affect the heater circuit activation, and replace if confirmed faulty.
• Clean and reattach earth connections: Check all lambda sensor ground connections, thoroughly clean corroded contacts and make tight, clean connections.