Faulty Signal. Permanent Fault

Checking The Rear Heated Oxygen Sensor
- Ignition off.
- Wait for approx. 150 seconds (cars with immobilizer 245 seconds).
- Disconnect rear heated oxygen sensor (HO2S) (gray connector).
- Connect an ohmmeter between heated oxygen sensor connector terminals 3 and 4 (heated oxygen sensor side).
- The ohmmeter should read 50 ohms to infinite resistance.

If reading is OK:
^ Check cable between rear heated oxygen sensor terminal 4 and control module # A34 for a short-circuit to the cable between rear heated oxygen sensor terminal 3 and engine control module (ECM) # A19.
^ Then proceed to Verification section below.

If reading is incorrect:
^ Try a new rear heated oxygen sensor.
^ Then proceed to Verification section below.





Verification
- After carrying out the repair, check that the fault has been remedied as follows.
- Ignition of.
- Front and rear heated oxygen sensors connected.
- Engine control module connected.
- Start the engine and idle it.
- Go into diagnostic test menu.
- Watch EFI-153 and EFI-212, wait until the status of EFI-153 and EFI-212 goes over to tested. This can take up to 15 minutes after the engine has been started.
- Read diagnostic trouble codes. If EFI-153 or EFI-212 are stored they should have the status of intermittent faults.

If reading is OK:
^ Fault corrected.

If reading is incorrect:
^ Proceed to test step below.

Fault-tracing information
The verification result shows that the fault persists.

- Do you want to exit fault-tracing?

Yes:
^ Fault not corrected.

No:
^ Re4turn to Checking The Rear Heated Oxygen Sensor section above.