P0051

P0051-O2 SENSOR 2/1 HEATER CIRCUIT LOW





For a complete wiring diagram refer to Diagrams/Electrical.

- When Monitored:

Battery voltage above 10.6 volts, ASD is powered up, and O2 heater is on.

- Set Condition:

Desired state does not match Actual state. One Trip Fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test

1. O2 SENSOR HEATER OPERATION

Turn the ignition off.

NOTE: Wait a minimum of 8 minutes to allow the O2 Sensor to cool down before continuing the test. Allow the O2 Sensor voltage to stabilize at 5.0 volts.

Ignition on, engine not running.

With a scan tool, actuate the O2 Heater Test.

NOTE: The DTC needs to be cleared before actuating the Heater Test, if the DTC is not cleared, the Heater Test may not be allowed to actuate.

With a scan tool, monitor 2/1 O2 Sensor voltage for at least 2 minutes.

Does the O2 Sensor voltage stay above 4.5 volts?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

2. O2 HEATER ELEMENT

Turn the ignition off.

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

Disconnect the 2/1 O2 Sensor harness connector.

Measure the resistance across the O2 Sensor Heater element, between the Heater Control terminal and the Heater ground terminal at the component.

NOTE: O2 Heater Element resistance values should be measured at 21.10 C (700 F). The resistance value will vary with different temperature values.

Is the O2 Sensor Heater Element resistance between 2.0 and 30.0 ohms?

Yes

- Go To 3

No

- Replace the O2 Sensor.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

3. O2 SENSOR





Ignition on, engine not running.

With a scan tool, actuate the O2 Heater Test with the O2 Sensor harness connector still disconnected.

NOTE: The DTC needs to be cleared before actuating the Heater Test, if the DTC is not cleared, the Heater Test may not be allowed to actuate.

Using a 12-volt test light connected to ground, probe the (K199) O2 2/1 Heater Control circuit in the O2 Sensor harness connector.

Does the test light illuminate brightly and flash on and off during the actuation?

Yes

- Replace the O2 Sensor.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 4

4. (K199) O2 2/1 HEATER CONTROL CIRCUIT SHORTED TO GROUND





Turn the ignition off.

Disconnect the C2 PCM harness connector.

Measure the resistance between ground and the (K199) O2 2/1 Heater Control circuit in the O2 Sensor harness connector.

Is the resistance below 5.0 ohms?

Yes

- Repair the short to ground in the (K199) O2 2/1 Sensor Heater Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 5

5. PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

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.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test