Diagnostic Test

1) O2 SENSOR BELOW 1.5 VOLTS
Start the engine.

Allow the engine to reach normal operating temperature.

With a scan tool, read the 1/1 O2 Sensor voltage.

Is the voltage below 1.5 volts?

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) (K41) O2 SENSOR 1/1 SIGNAL CIRCUIT
Turn the ignition off.

Disconnect the 1/1 O2 Sensor harness connector.

Ignition on, engine not running.

With a scan tool, monitor the 1/1 O2 Sensor voltage.

Is the 1/1 O2 Sensor voltage above 4.8 volts?

Yes
1. Go To 3).
No
1. Go To 5).
3) O2 SENSOR

Fig 1: MEASURING FOR VOLTAGE ON THE O2 RETURN UPSTREAM CIRCUIT
Courtesy of DAIMLERCHRYSLER CORP.

Measure the voltage on the (K902) O2 Return Upstream circuit in the O2 Sensor harness connector.

Is the voltage at 2.5 volts?

Yes
1. Replace the O2 Sensor.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Go To 4).
4) (K902) O2 RETURN UPSTREAM CIRCUIT SHORTED TO GROUND

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

Turn the ignition off.

Disconnect the PCM harness connectors.

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

Is the resistance below 100 ohms?

Yes
1. Repair the short to ground in the (K902) O2 Return Upstream circuit.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Go To 8).
5) (K41) O2 SENSOR 1/1 SIGNAL CIRCUIT SHORTED TO GROUND

Fig 3: MEASURING RESISTANCE BETWEEN GROUND AND THE O2 SENSOR 1/1 SIGNAL CIRCUIT
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the PCM harness connectors.

Measure the resistance between ground and the (K41) O2 Sensor 1/1 Signal circuit in the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes
1. Repair the short to ground in the (K41) O2 Sensor 1/1 Signal circuit.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Go To 6).
6) (K41) O2 SENSOR 1/1 SIGNAL CIRCUIT SHORTED TO (K902) O2 RETURN UPSTREAM CIRCUIT

Fig 4: MEASURING RESISTANCE BETWEEN THE O2 SENSOR 1/1 SIGNAL CIRCUIT AND O2 RETURN UPSTREAM CIRCUIT
Courtesy of DAIMLERCHRYSLER CORP.

Measure the resistance between the (K41) O2 Sensor 1/1 Signal circuit and the (K902) O2 Return Upstream circuit in the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes
1. Repair the short between the (K902) O2 Return Upstream circuit and the (K41) O2 Sensor 1/1 Signal circuit.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Go To 7).
7) (K41) O2 SENSOR 1/1 SIGNAL CIRCUIT SHORTED TO THE (Z902) O2 1/1 HEATER GROUND CIRCUIT

Fig 5: MEASURING RESISTANCE BETWEEN THE O2 SENSOR 1/1 SIGNAL CIRCUIT AND O2 1/1 HEATER GROUND CIRCUIT
Courtesy of DAIMLERCHRYSLER CORP.

Measure the resistance between the (K41) O2 Sensor 1/1 Signal circuit and the (Z902) O2 1/1 Heater ground circuit in the O2 Sensor harness connector.

Is the resistance below 100 ohms?

Yes
1. Repair the short between the (Z902) O2 1/1 Heater ground circuit and the (K41) O2 Sensor 1/1 Signal circuit.
2. Perform (NGC) POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - NGC POWERTRAIN VERIFICATION TEST VER - 1) .
No
1. Go To 8).
8) 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
1. Repair as necessary.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Replace and program the Powertrain Control Module per Service Information. Refer to MODULE-POWERTRAIN CONTROL and STANDARD PROCEDURE - PCM/ECM/SKREEM PROGRAMMING .
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .