Problem

The engine is running unevenly, fuel consumption has increased and the ‘check engine’ warning lamp is illuminated.Fault code P0141 - O2 sensor heater circuit (bank 1, sensor 2) malfunction is stored in the engine control unit (ECU).The fault re-appears after a new oxygen sensor has been fitted.

Cause
The wiring harness that is connected from the oxygen sensor to the ECU has a high electrical resistance value, causing the issues listed above.

Solution
Before replacing the oxygen sensor, a test of the wiring harness that connects the oxygen sensor to the ECU should be completed. This is due to an intermittent out-of-tolerance electrical resistance reading, causing the P0141 fault code. If the fault is detected in the wiring harness, either a replacement harness will be required, or a repair on the existing harness will have be carried out. When  the  necessary work  has  been  completed,  clear  the  fault  code  from  the  ECU  using  a  suitable  diagnostic  tester and perform a road test.

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