Diagnostic Tests

1) O2 SENSOR BELOW 0.5 VOLT
Start the engine.

Allow the engine to idle.

With the scan tool, read the O2 Sensor voltage.

Is the voltage below 0.05?

Yes
1. Go To 2).
No
1. Refer to the INTERMITTENT CONDITION diagnostic procedure.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
2) O2 SENSOR OPERATION
WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.

Start the engine.

Disconnect the O2 Sensor harness connector.

With the scan tool, monitor the O2 Sensor voltage.

Is the O2 Sensor voltage above 0.05?

Yes
1. Replace the O2 Sensor
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Go To 3).
3) (K41) O2 SENSOR SIGNAL CIRCUIT SHORTED TO GROUND

Fig 1: MEASURING RESISTANCE OF THE O2 SENSOR SIGNAL CIRCUIT
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the O2 Sensor harness connector.

Disconnect the PCM harness connector.

Measure the resistance of the (K41) O2 Sensor Signal circuit in the O2 Sensor harness connector to ground.

Is the resistance below 100 ohms?

Yes
1. Repair the (K41) O2 Sensor Signal circuit for a short to ground.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Go To 4).
4) (K41) O2 SENSOR SIGNAL CIRCUIT SHORTED TO (K902) SENSOR GROUND CIRCUIT

Fig 2: MEASURING RESISTANCE BETWEEN THE O2 SENSOR SIGNAL CIRCUIT AND THE O2 SENSOR GROUND CIRCUIT
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the O2 Sensor harness connector.

Disconnect the PCM harness connector.

Measure the resistance between the (K41) O2 Sensor Signal circuit and the (K902) O2 Sensor ground circuit in the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes
1. Repair the (K41) O2 Sensor Signal circuit for a short to the (K902) O2 Sensor ground circuit.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Go To 5).
5) (K41) O2 SENSOR SIGNAL CIRCUIT SHORTED TO (K99) HEATER CONTROL CIRCUIT

Fig 3: MEASURING RESISTANCE BETWEEN THE O2 SENSOR SIGNAL CIRCUIT AND THE O2 SENSOR HEATER CONTROL CIRCUIT
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the O2 Sensor harness connector.

Disconnect the PCM harness connector.

Measure the resistance between the (K41) O2 Sensor Signal circuit and the (K99) O2 Sensor Heater control circuit in the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes
1. Repair the (K41) O2 Sensor Signal circuit for a short to the (K99) O2 Sensor Heater control circuit.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Go To 6).
6) PCM
NOTE: Before Continuing: Disconnect the PCM harness connector and check the related wiring 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.

If there are no possible causes remaining, view repair.

Repair
1. Replace and program the Powertrain Control Module in accordance with the Service Information. (Refer to STANDARD PROCEDURE - PCM/ECM/SKREEM PROGRAMMING) .
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .