P0031

P0031-O2 SENSOR 1/1 HEATER CIRCUIT LOW





For complete wiring diagrams refer to Diagrams/Electrical.


- When Monitored:

Continuously during O2 heater operation with battery voltage between 10.4 and 15.75 volts.

- Set Condition:

The PCM detects that the O2 sensor heater element input is below the minimum acceptable voltage. One trip fault. Three good trips to turn off the MIL.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test


1. DTC IS ACTIVE

Start the engine and allow it to idle for at least 60 seconds.


WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

With a scan tool, select View DTCs.

Is the DTC Active at this time?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition


2. O2 HEATER ELEMENT

Turn the ignition off.


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

Disconnect the 1/1 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 21.1° C (70° 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 POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

3. (K99) O2 1/1 HEATER CONTROL CIRCUIT SHORTED TO GROUND





Turn the ignition off.

Disconnect the C2 PCM harness connector.

Measure the resistance between ground and the (K99) O2 1/1 Heater Control circuit in the O2 Sensor harness connector.

Is the resistance below 5.0 ohms?

Yes

- Repair the short to ground in the (K99) O2 1/1 Heater Control circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 4

4. EXCESSIVE RESISTANCE IN THE (K99) O2 1/1 HEATER CONTROL CIRCUIT





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 Miller Special Tool #8815 to perform diagnosis.

Measure the resistance of the (K99) O2 1/1 Heater Control circuit between the 1/1 Oxygen Sensor harness connector and the appropriate terminal of special tool #8815.

Is the resistance below 0.5 ohms?

Yes

- Go To 5

No

- Repair the excessive resistance in the (K99) O2 1/1 Heater Control circuit.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

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 POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

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