P0161
P0161-O2 SENSOR 2/2 HEATER PERFORMANCE
Theory of Operation
This diagnostic provides a continuous check of the O2 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:
Continuously during O2 sensor heater operation with battery voltage between 10.4 and 15.75 volts and no O2 sensor circuit DTCs present.
- Set Condition:
The Powertrain Control Module (PCM) detects no temperature change in the O2 sensor heater element when the heater circuit is active. The heater temperature is obtained by measuring the heater resistance and calculating the heater temperature. 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. 2/2 OXYGEN SENSOR HEATER CONTROL OPERATION
NOTE: Allow the sensor to cool to ambient temperature before continuing. The voltage should stabilize between 4.6 and 5.0 volts.
1. Turn the ignition on.
2. With a scan tool, actuate the 2/2 Oxygen Sensor heater control.
3. With the scan tool, monitor the 2/2 Oxygen Sensor voltage for at least two minutes.
Does the voltage stay above 4.5 volts?
Yes
- Go To 2
No
- Perform the CHECKING FOR AN INTERMITTENT DTC diagnostic procedure. Checking for an Intermittent DTC.
2. 2/2 OXYGEN SENSOR
1. Turn the ignition off.
NOTE: Allow the sensor to cool to ambient temperature before continuing. The voltage should stabilize between 4.6 and 5.0 volts.
2. Disconnect the 2/2 Oxygen Sensor harness connector.
3. Measure the resistance of the O2 sensor heater element across the 2/2 Oxygen Sensor connector between the heater control terminal and the ground terminal.
NOTE: O2 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 between 2.0 and 30.0 Ohms?
Yes
- Go To 3
No
- Replace the 2/2 Oxygen Sensor.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.
3. (K399) O2 2/2 HEATER CONTROL CIRCUIT OPEN OR HIGH RESISTANCE
1. Disconnect the C3 Powertrain Control Module (PCM) harness connector.
CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals, resulting in poor terminal to pin connection. Install PCM Pinout Box 8815 to perform diagnosis.
2. Measure the resistance of the (K399) O2 2/2 Heater Control circuit between the 2/2 Oxygen Sensor harness connector and the appropriate terminal of PCM Pinout Box 8815.
Is the resistance below 0.5 of an Ohm?
Yes
- Go To 4
No
- Repair the (K399) O2 2/2 Heater Control circuit for an open circuit or high resistance.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.
4. (Z931) GROUND CIRCUIT OPEN OR HIGH RESISTANCE
1. Using a 12-volt test light connected to 12 volts, check the (Z931) Ground circuit in the 2/2 Oxygen Sensor harness connector.
NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.
Is the test light illuminated and bright?
Yes
- Go To 5
No
- Repair the (Z931) Ground circuit for an open circuit or high resistance.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.
5. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the 2/2 Oxygen Sensor 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.
4. Verify that there is good pin to terminal contact in the 2/2 Oxygen Sensor and Powertrain Control Module connectors.
5. Perform any Technical Service Bulletins that may apply.
Were any problems found?
Yes
- Repair as necessary.
- Perform the PCM VERIFICATION TEST. PCM Verification Test.
No
- Replace and program the Powertrain Control Module (PCM).
- Perform the PCM VERIFICATION TEST. PCM Verification Test.