Fault code P0142 – a step-by-step guide to diagnosing and fixing it

Error code P0142 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system detects a fault in the heating circuit of lambda sensor 2 in bank 1. This DTC P0142 indicates a fault in the heating function of the downstream oxygen sensor, which is required for correct exhaust gas purification and catalytic converter monitoring.

What can cause this error code?

• Defective heating of lambda sensor 2 bank 1
• Damaged or corroded cable to the oxygen sensor
• Loose or corroded plug connections
• Blown fuse in the heating circuit
• Defective engine control unit (ECU)
• Short circuit or interruption in the wiring
• Faulty ground wire of the lambda sensor

What symptoms occur in parallel with fault code P0142?

• Check engine light: The check engine light is permanently illuminated on the dashboard
• Increased fuel consumption: The vehicle consumes more fuel than usual
• Poor exhaust values: Increased emissions during the emissions test
• Uneven engine running: The engine runs unevenly or jerks when idling
• Starting problems: Prolonged starting process, especially when the engine is cold
• Loss of power: Reduced engine power and poorer acceleration

How can the problem with fault code P0142 be rectified?

• Repairing fault code P0142 requires a systematic diagnosis of the lambda sensor heating circuit.
• Replace the lambda sensor: Replace defective oxygen sensor 2 bank 1 completely, including heating element and sensor part (cost: €80-200 plus labor)
• Repair wiring: Locate damaged cables to the oxygen sensor and replace with new cables or have professionally repaired
• Clean plug connections: Remove corroded or loose plugs to the lambda sensor, clean with contact spray and connect firmly
• Check and replace the fuse: Identify blown fuse in the fuse box and replace with a new fuse of the same amperage
• Check engine control unit: Have ECU diagnostics carried out and, if defective, repair or replace the control unit (costs: €500-1500)
• Replace the entire wiring: In the event of multiple cable damage, have the entire wiring harness to the lambda sensor replaced by a specialist workshop