Signal Too High. Permanent Fault

Checking Signal Cable
- Ignition off.
- Disconnect heated oxygen sensor (HO2S) (front heated oxygen sensor: black connector, rear heated oxygen sensor: gray connector).
- Ignition on.
- Connect a voltmeter between the heated oxygen sensor connector terminal 2 (engine control module (ECM) side) and ground.
- The voltmeter should read approx. 0 Volts.

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

If reading is incorrect:
^ Check cable between heated oxygen sensor terminal 2 and engine control module # A14 (for diagnostic trouble code (DTC) EFI-521)/ # A29 (for diagnostic trouble code EFI-522) for a short-circuit to supply voltage.
^ Then proceed to Verification section below.





Verification
- After carrying out the repair, check that the fault has been remedied as follows.
- Ignition off.
- Front and rear heated oxygen sensors connected.
- Engine control module connected.
- Start the engine and idle it.
- Go into verification menu.
- Watch the diagnostic trouble code to be verified.
- Wait until its status goes over to tested.
- This can take up to 5 minutes for the EFI-521.
- This can take up to 15 minutes for the EFI-522.
- Read diagnostic trouble codes.
- If EFI-521 or EFI-522 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:
^ Return to Checking Signal Cable section above.