Repair procedures (plant/service)

This malfunction automatically triggers an active test (collateral fault stored in the control module's fault memory!).

1. Read out results of active test (are other faults still stored in the control module's fault memory)? => Then continue at this point!)
2. Initiate system test for reversed O2 sensors. Follow instructions for system test.
3. If the system test fails to produce a result then
4. Visual inspection of wiring and plugs
5. Electrical check of wiring
6. Replace wiring or plugs as indicated
7. Check exhaust system forward of downstream (post-cat) O2 sensor for leaks
8. Replace upstream (pre-cat) O2 sensor