Signal Missing. Permanent Fault

Checking Signal Cable (+), Rear Heated Oxygen Sensor
- Ignition off.
- Wait approx. 150 seconds.
- Disconnect rear heated oxygen sensor (HO2S) (gray connector).
- Connect an ohmmeter between heated oxygen sensor connector at terminal 4 (towards control module) and ground.
- The ohmmeter should read approx. 50K ohms.

If reading is OK:
^ Proceed to Checking Signal Cable (-), Rear Heated Oxygen Sensor section below.

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





Checking The Engine Control Module Connector
- Ignition off.
- Rear heated oxygen sensor disconnected.
- Check engine control module (ECM) connector for contact resistance and oxidation and remedy.
- Engine control module connected.
- Connect an ohmmeter between heated oxygen sensor connector terminal 4 (control module side) and ground.
- The ohmmeter should read approx. 50K ohms.

If reading is OK:
^ The diagnostic trouble code (DTC) was caused by poor contact in the engine control module connector.
^ Then proceed to Verification section below.

If reading is incorrect:
^ Check cable between rear heated oxygen sensor terminal 4 and engine control module # A34 for an open-circuit.
^ Then proceed to Verification section below.





Checking Signal Cable (-), Rear Heated Oxygen Sensor
- Ignition off.
- Rear heated oxygen sensor disconnected.
- Connect an ohmmeter between heated oxygen sensor connector terminal 3 (control module side) and ground.
- The ohmmeter should read approx. 200 ohms.

If reading is OK:
^ Proceed to Checking Rear Heated Oxygen Sensor Signal section below.

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





Checking The Engine Control Module Connector
- Ignition off.
- Rear heated oxygen sensor disconnected.
- Check engine control module connector for contact resistance and oxidation and remedy.
- Engine control module connected.
- Connect an ohmmeter between heated oxygen sensor connector terminal 3 (control module side) and ground.
- The ohmmeter should read approx. 200 ohms.

If reading is OK:
^ The diagnostic trouble code was caused by poor contact in the engine control module connector.
^ Then proceed to Verification section below.

If reading is incorrect:
^ Check cable between rear heated oxygen sensor terminal 3 and engine control module terminal # A19 for an open-circuit.
^ Then proceed to Verification section below.





Checking Rear Heated Oxygen Sensor Signal
- Ignition off.
- Connect the rear heated oxygen sensor.
- Start the engine and idle it.
- Go into scrolling value list.
- Read off rear heated oxygen sensor value.
- The signal should rise above its middle value, (0.47 Volts), and settle between 0.1 - 0.9 Volts within approx. 10 minutes.

If reading is OK:
^ The diagnostic trouble code has been caused by poor contact in the rear heated oxygen sensor connector. Check that the pins in the connector are intact. Do not apply rust solvent spray or grease to the heated oxygen sensor connector.
^ 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:
^ Return to Checking Signal Cable (+), Rear Heated Oxygen Sensor section above.