P0051
P0051-O2 SENSOR 2/1 HEATER CIRCUIT LOWP0051-O2 Sensor 2/1 Heater Circuit Low:
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.
POSSIBLE CAUSES
- (K199) O2 2/1 heater control circuit shorted to ground
- O2 sensor
- PCM
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.
With a scan tool, monitor 2/1 O2 Sensor voltage for at least 2 minutes.
Q: Does the O2 Sensor voltage stay above 4.5 volts?
YES: Go To 2
NO: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Component Tests and General Diagnostics
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 70° F (21.1° C). The resistance value will vary with different temperature values.
Q: 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.
Using a 12-volt test light connected to ground, probe the (K199) O2 2/1 Heater Control circuit in the O2 Sensor harness connector.
Q: 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.
Q: 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.
Q: 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