Diagnostic Test

1) O2 SENSOR BELOW 2.52 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 2.52 volts?

Yes
1. Go To 2).
No
1. Refer to INTERMITTENT CONDITION .
2. Perform 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 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: Checking O2 Sensor Return Upstream Circuit Voltage
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 POWERTRAIN VERIFICATION TEST .
No
1. Go To 4).
4) (K902) O2 RETURN UPSTREAM CIRCUIT SHORTED TO GROUND

Fig 2: Checking O2 Sensor Return Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the C1 PCM harness connector.

Measure the resistance between ground and the (K902) O2 Return Upstream 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 POWERTRAIN VERIFICATION TEST .
No
1. Go To 8).
5) (K41) O2 SENSOR 1/1 SIGNAL CIRCUIT SHORTED TO GROUND

Fig 3: Checking O2 Sensor Signal Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off.

Disconnect the C1 and C2 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 POWERTRAIN VERIFICATION TEST .
No
1. Go To 6).
6) (K41) O2 SENSOR 1/1 SIGNAL CIRCUIT SHORTED TO THE (K902) O2 RETURN UPSTREAM CIRCUIT

Fig 4: Checking O2 Sensor Signal Circuit & Return 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 POWERTRAIN VERIFICATION TEST .
No
1. Go To 7).
7) (K41) O2 SENSOR 1/1 SIGNAL CIRCUIT SHORTED TO THE (Z42) O2 1/1 HEATER GROUND CIRCUIT

Fig 5: Checking O2 Sensor Signal Circuit & Heater Ground Circuit
Courtesy of DAIMLERCHRYSLER CORP.

Measure the resistance between the (K41) O2 Sensor 1/1 Signal circuit and the (Z42) 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 (Z42) O2 1/1 Heater ground circuit and the (K41) O2 Sensor 1/1 Signal circuit.
2. Perform POWERTRAIN VERIFICATION TEST .
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 POWERTRAIN VERIFICATION TEST .
No
1. Replace and program the Powertrain Control Module per Service Information.
2. Perform POWERTRAIN VERIFICATION TEST .