P0161

P0161-O2 SENSOR 2/2 HEATER PERFORMANCE





For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

This diagnostic provides a continuous check of the O2 Sensor Heater circuit during operation. The heater circuit is momentarily disabled to allow a resistance measurement to be taken to infer heater temperature. The current delivery to the heater is duty cycled to maintain a specific target temperature. The error from the target temperature is continuously monitored to assess heater performance.

- When Monitored:
Engine running and heater duty cycle greater than 0%. Battery voltage greater than 11.0 Volts.

- Set Condition:
No sensor output is received when the PCM powers up the O2 Sensor Heater. Two trip fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. O2 SENSOR HEATER OPERATION
1. Turn the ignition off.

NOTE: Wait a minimum of eight minutes to allow the O2 Sensor to cool down before continuing the test. Allow the O2 Sensor voltage to stabilize between 4.6 and 5.0 Volts.

2. Ignition on, engine not running.
3. With the scan tool, actuate the O2 Heater Test.
4. With the scan tool, monitor O2 Sensor 2/2 voltage for at least two minutes.

Does the voltage stay above 4.5 Volts?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test

2. O2 SENSOR 2/2 HEATER ELEMENT
1. Turn the ignition off.

NOTE: Allow the O2 sensor to cool down to room temperature.

2. Disconnect the O2 Sensor 2/2 harness connector.
3. Measure the resistance of the O2 Sensor Heater Element across the O2 Sensor, between the O2 Heater Control terminal and the O2 Heater ground terminal.

NOTE: O2 Sensor 2/2 Heater Element resistance values should be measured at 21.1° C (70° F). The resistance value will vary with different temperature values.

Is the resistance of the O2 Sensor 2/2 Heater Element between 2.0 and 30.0 Ohms?

Yes

- Go To 3

No

- Verify that there is good pin to terminal contact in the O2 Sensor 2/2 and Powertrain Control Module connectors. If OK, replace the O2 Sensor 2/2. Oxygen Sensor - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

3. (K399) O2 SENSOR 2/2 HEATER CONTROL CIRCUIT OPEN




1. Disconnect the PCM C2 harness connector.
2. Measure the resistance of the (K399) O2 Sensor 2/2 Heater Control circuit from the O2 Sensor 2/2 connector to the PCM C2 harness connector.

Is the resistance below 0.5 Ohm?

Yes

- Go To 4

No

- Repair the excessive resistance in the (K399) O2 Sensor 2/2 Heater Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

4. O2 SENSOR 2/2 HEATER GROUND CIRCUIT OPEN




1. Measure the resistance between ground and the O2 Sensor 2/2 Heater ground circuit in the O2 Sensor 2/2 harness connector.

Is the resistance below 0.5 Ohm?

Yes

- Go To 5

No

- Repair the excessive resistance in the O2 Sensor 2/2 Heater ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Oxygen Sensor 2/2 and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Oxygen Sensor 2/2 and Powertrain Control Module connectors.
4. Perform any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module. Powertrain Control Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.