P0051 02 SENSOR HEATER CIRCUIT LOW2/1: Possible Harness damage.;Check Fuse #16 in PDC, if it's blown and perform power train test for the code looking for a short to ground. A production change was preformed on vehicles built after 6/2/03 to take care of erroneous codes, a software fix is needed to correct vehicles built before 6/2/03 this will be in the form of a software flash
Check for excessive heat from exhaust melting the harness by the 02 sensor
Ignition on, engine not running.
With the scan tool, read DTCs
NOTE: If P0136 is set with the P0031 or P0051, inspect the related fused and
repair as necessary.
With the scan tool, actuate the O2 Heater test.
Monitor the O2 Heater Voltage for 5 minutes.
Did the voltage drop down close to zero during the Heater test?
Yes The conditions to set this code are not currently present
No Go To 2NOTE: Stop the actuation before continuing.
Turn the ignition off.
Disconnect the O2 Sensor harness connector.
Measure the resistance of the O2 Heater Element at the O2 Sensor connector
The resistance value for a 4.0L O2 Heater element is 4.0 to 5.0 ohms at 70°F
NOTE: The resistance value will increase with warmer temperatures.
Is the resistance within the listed specifications?
Yes Go To 3
No Replace the O2 Sensor.
Ignition on, engine not running, and the Sensor harness connector still disconnected.
With the scan tool, actuate the O2 Heater Test.
Using a 12-volt test light connected to ground, check for voltage on the Fused
ASD Relay Output in the O2 Sensor harness connector.
Does the test light illuminate brightly?
Yes Go To 4
No Repair the open or short to ground in the Fused ASD
Relay/O2 Heater Supply circuit. Inspect the related fuse and repair as necessary.
NOTE: Stop the actuation before continuing.
Turn the ignition off.
Disconnect the PCM harness connectors.
Measure the resistance of the O2 Heater Control circuit (PWM) from the O2 Sensor
harness connector to the PCM harness connector.
Is the resistance below 5.0 ohms?
Yes Go To 5
No Repair the excessive resistance in the PWM Heater Control circuit.
Measure the resistance between ground and the O2 Heater Control (PWM) circuit at
the O2 Sensor harness connector.
Is the resistance below 100 ohms?
Yes Repair the short to ground in the Heater Control (PWM) circuit.
No Go To 6
NOTE: Before continuing, check the PCM harness connector terminals for
corrosion, damage, or terminal push out. Repair as necessary.
inspect the wire harness and connectors. Pay
particular attention to all Power and Ground circuits.
If there are no possible causes remaining
Replace and program the Power train Control Module
since it is an early build a software update may fix your concern without doing all of this, the normal charge for a software update is 1 hour
P0051-O2 SENSOR 2/1 HEATER CIRCUIT LOW
When Monitored: Battery voltage above 10.6 volts, ASD is powered up, and O2 heater is
Set Condition: Desired state does not equal Actual state.
O2 HEATER TEST
O2 SENSOR HEATER ELEMENT
(F142) FUSED ASD RELAY OUTPUT CIRCUIT OPEN
HEATER CONTROL CIRCUIT OPEN
HEATER CONTROL CIRCUIT SHORTED TO GROUND