Fault code P0140 – a step-by-step guide to diagnosing and fixing it

Error code P0140 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has detected that the rear lambda sensor (bank 1, sensor 2) after the catalytic converter is showing no activity or is not working properly. This DTC P0140 indicates problems with the oxygen sensor, which is responsible for monitoring the catalytic converter efficiency.

What can cause this fault code?

• Defective rear lambda sensor (bank 1, sensor 2)
• Damaged or corroded cable connections to the oxygen sensor
• Loose or defective plug connections
• Interrupted heating circuit of the lambda sensor
• Defective fuse in the lambda sensor heating circuit
• Damaged exhaust pipe or leaks upstream of the sensor
• Engine control unit malfunction
• Contamination of the sensor by oil or coolant

What symptoms occur in parallel with fault code P0140?

• Check engine light: The warning light lights up continuously or flashes
• Increased fuel consumption: The vehicle consumes more fuel than usual
• Unsteady idling: The engine runs unevenly at idle speed
• Reduced engine power: Noticeable loss of power when accelerating
• Exhaust problems: Increased emission values during the emissions test
• Jerking: The vehicle may jerk or stutter while driving

How can the problem with error code P0140 be rectified?

• Repairing trouble code P0140 requires a systematic approach to identifying and eliminating the cause.
• Replace the lambda sensor: Replace the defective rear oxygen sensor (bank 1, sensor 2) with a new OEM-compliant sensor and install it properly
• Repair cable connections: Locate damaged or corroded cables to the lambda sensor, repair or replace completely
• Clean plug connections: Clean all electrical connections to the sensor, treat with contact spray and connect firmly
• Check and replace the fuse: Check the fuse of the lambda sensor heating circuit and replace with a new one if necessary
• Seal the exhaust system: Detect leaks in the exhaust pipe upstream of the sensor and have them professionally welded or sealed
• Diagnose the engine control unit: Check the control unit for defects and have it repaired or replaced if necessary