P0051

SYMPTOM
P0051-02 SENSOR 2/1 HEATER CIRCUIT LOW

WHEN MONITORED
Battery voltage above 10.6 volts, ASD is powered up, and 02 heater is on.

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

POSSIBLE CAUSES
- (K199) 02 2/1 HEATER CONTROL CIRCUIT SHORTED TO GROUND
- 02 SENSOR
- PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Scan Tool Testing and Procedures

DIAGNOSTIC TEST
1. 02 SENSOR HEATER OPERATION





Turn the ignition off.

Note: Wait a minimum of 8 minutes to allow the 02 Sensor to cool down before continuing the test. Allow the 02 Sensor voltage to stabilize at 5.0 volts.

Ignition on, engine not running. With a scan tool, actuate the 02 Heater Test. With a scan tool, monitor 2/1 02 Sensor voltage for at least 2 minutes.
Does the 02 Sensor voltage stay above 4.5 volts?
Yes>> Go To 2
No>> Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5. Powertrain Verification Test - Ver 5

2. 02 HEATER ELEMENT Turn the ignition off.

Note: Allow the 02 Sensor to cool down to room temperature.

Disconnect the 2/1 02 Sensor harness connector.
Measure the resistance across the 02 Sensor Heater element, between the Heater Control terminal and the Heater ground terminal at the component.

Note: 02 Heater Element resistance values should be measured at 70 °F (21.1 °C). The resistance value will vary with different temperature values.

Is the 02 Sensor Heater Element resistance between 2.0 and 30.0 ohms?
Yes>> Go To 3
No>> Replace the 02 Sensor. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.

3. 02 SENSOR





Ignition on, engine not running.
With a scan tool, actuate the 02 Heater Test with the 02 Sensor harness connector still disconnected.
Using a 12-volt test light connected to ground, probe the (K199) 02 2/1 Heater Control circuit in the 02 Sensor harness connector.
Does the test light illuminate brightly and flash on and off during the actuation?
Yes>> Replace the 02 Sensor. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Go To 4

4. (K199) 02 2/1 HEATER CONTROL CIRCUIT SHORTED TO GROUND





Turn the ignition off.
Disconnect the PCM harness connectors.
Measure the resistance between ground and the (K199) 02 2/1 Heater Control circuit in the 02 Sensor harness connector.
Is the resistance below 5.0 ohms?
Yes>> Repair the short to ground in the (K199) 02 2/1 Sensor Heater Control circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
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 (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Replace and program the Powertrain Control Module per Service Information. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.