Fault code P0161 – a step-by-step guide to diagnosing and fixing it

Error code P0161 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has detected a defect in the heating circuit of lambda sensor 2 (bank 2). This DTC P0161 trouble code indicates problems with the heating of the downstream oxygen sensor, which is required for proper exhaust gas purification and catalytic converter monitoring.

What can cause this fault 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
• Interruption in the sensor heater circuit

What symptoms occur in parallel with fault code P0161?

• Increased fuel consumption: The vehicle consumes more fuel than usual because the mixture control is not functioning optimally.
• Poor engine performance: The engine runs unevenly or has less power, especially when starting cold.
• Exhaust problems: Increased emission values and possible failure of the emissions test.
• Jerking at idle: The engine runs unevenly or stutters when idling.
• Delayed heat-up phase: The lambda sensor does not reach its operating temperature quickly enough.

How can the problem with fault code P0161 be rectified?

• Repairing fault code P0161 requires a systematic diagnosis of the lambda sensor heater.
• Check and replace the fuse: Check the lambda sensor heater fuse in the fuse box and replace it if necessary.
• Replace the lambda sensor completely: Replace the defective lambda sensor 2 (bank 2) with a new, original compatible sensor including heating element.
• Repair wiring: Check all cables to the lambda sensor for damage, breaks or chafing and repair or replace defective cables.
• Clean plug connections: Clean the lambda sensor plugs with contact spray and ensure that they are firmly seated to eliminate corrosion and loose contacts.
• Diagnose the engine control unit: Have the ECU tested at a specialist workshop and replaced or repaired if defective.