When the rear oxygen sensor and the front oxygen sensor fail, the following repair steps are usually required:

1. Fault diagnosis: First of all, it is necessary to use automobile diagnostic tools to diagnose the fault of the vehicle to determine whether there is a problem with the front oxygen sensor or the rear oxygen sensor. Diagnostic tools can read the fault code of the vehicle and help to determine the specific cause of the fault.

2. Replace the sensor: Once it is determined that the oxygen sensor is faulty, it is necessary to replace the faulty sensor with a new one that works normally. Sensor replacement usually requires removing related components, such as exhaust pipe, and then installing a new sensor, and ensuring a firm connection.

3. Recalibration: After replacing the sensor, some vehicles may need to recalibrate or learn the sensor. This usually requires the use of professional diagnostic tools to ensure that the sensor can work normally and communicate correctly with the control system of the vehicle.

4. Clear the fault code: After replacing the sensor and recalibrating, it is necessary to use diagnostic tools to clear the fault code of the vehicle. This can reset the fault indicator light of the vehicle and ensure the normal operation of the vehicle.

5. Testing and debugging: Finally, it is necessary to carry out a road test or test in the working state of the vehicle to ensure that everything is normal after the sensor is replaced. If the problem still exists, further inspection and debugging may be needed.

Generally speaking, repairing the faults of automobile rear oxygen sensor and front oxygen sensor requires fault diagnosis, sensor replacement, recalibration, fault code clearing and testing. For some complicated faults, it is suggested to seek professional automobile maintenance technicians to repair them to ensure the accuracy and reliability of the repair work.