Signal Missing. Permanent Fault

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

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

If reading is incorrect:
^ Proceed to: Checking ECM Connector section below.





Checking ECM 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 4 (engine control module side) and ground.
- The ohmmeter should read approx. 50 K ohms.

If reading is OK:
^ The cause of the diagnostic trouble code (DTC) has been loose connections in the engine control module connector.
^ 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.
^ 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 (engine control module side) and ground.
- The ohmmeter should read approx. 140 ohms.

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

If reading is incorrect:
^ Proceed to: Checking ECM Connector section below.





Checking ECM 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 (engine control module side) and ground.
- The ohmmeter should read approx. 140 ohms.

If reading is OK:
^ The diagnostic trouble code was caused by loose connections in the engine control module connector.
^ Proceed to: Verification section below.

If reading is incorrect:
^ Check cable between rear heated oxygen sensor terminal 3 and engine control module # A19 for an open-circuit.
^ 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 values.
- Read off rear heated oxygen sensor value.
- The signal should rise above its mean value, (0.47 Volts), and settle between 0. 1 - 0.9 Volts within approx. 10 minutes.

If reading is OK:
^ The cause of the diagnostic trouble code has been loose connections 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.
^ Proceed to: Verification section below.

If reading is incorrect:
^ Try a new rear heated oxygen sensor.
^ 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 diagnostic test menu.
- Watch EFI-153, wait until the status of EFI-153 switches to tested. This can take up to 15 minutes after the engine has been started.
- Read diagnostic trouble codes. If EFI-153 is stored it should have intermittent fault status.

If reading is OK:
^ Fault corrected.

If reading is incorrect:
^ Proceed to: Fault-tracing Information section below.

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

- Do you want to exit fault-tracing?

Yes:
^ Fault not corrected.

No:
^ Proceed to: Checking Signal Cable (+), Rear Heated Oxygen Sensor section above.