P0031-O2 SENSOR 1/1 HEATER CIRCUIT LOW





For a complete wiring diagram Refer to Section 8W.



Possible Causes
(K99) O2 SENSOR 1/1 HEATER CONTROL CIRCUIT SHORTED TO GROUND
O2 SENSOR
PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).



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

Does the O2 Sensor voltage stay above 4.5 volts?

Yes


No

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 degrees C (70 degrees 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


No

3. O2 SENSOR



Ignition on, engine not running.
Using a 12-volt test light connected to ground, probe the (K99) O2 1/1 Heater Control circuit in the O2 Sensor harness connector.

NOTE: Make sure the test light is probing the circuit before actuating the Heater Test or a DTC may set and not allow the actuation.


With a scan tool, actuate the O2 1/1 Heater Test with the O2 Sensor harness connector still disconnected.

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

Yes


No

4. (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


No

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


No