Diagnostic Test

1) ACTIVE DTC
NOTE: Check for contaminants that may have damaged the O2 Sensor: contaminated fuel, unapproved silicone, oil and coolant.

Ignition on, engine not running.

NOTE: After the repairs have been made, verify proper O2 Sensor operation. If all the O2 Sensor voltage readings have not returned to normal, follow the diagnostic procedure for the remaining O2 Sensors.

With a scan tool, read DTCs.

Is the DTC active at this time?

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) EXHAUST LEAK
Start the engine.

Inspect the exhaust system for leaks between the engine and the O2 Sensors.

Are there any exhaust leaks?

Yes
1. Repair or replace the leaking exhaust parts as necessary.
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .
No
1. Go To 3).
3) (K141) O2 1/2 SIGNAL CIRCUIT

Fig 1: MEASURING FOR VOLTAGE ON THE O2 1/2 SIGNAL CIRCUIT
Courtesy of DAIMLERCHRYSLER CORP.

Turn the ignition off

Disconnect the 1/2 O2 Sensor harness connector.

Ignition on, engine not running.

Measure the voltage on the (K141) O2 1/2 Signal circuit in the O2 Sensor harness connector.

Is the voltage between 4.5 and 5.0 volts?

Yes
1. Go To 4).
No
1. Check the (K141) O2 1/2 Signal circuit for a short to ground, open, or short to voltage. If OK, 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) .
4) (K902) O2 DOWNSTREAM RETURN CIRCUIT

Fig 2: MEASURING FOR VOLTAGE ON THE O2 DOWNSTREAM RETURN CIRCUIT
Courtesy of DAIMLERCHRYSLER CORP.

Measure the voltage on the (K902) O2 Downstream Return circuit in the 1/2 O2 Sensor harness connector.

Is the voltage at 2.5 volts?

Yes
1. Go To 5).
No
1. Check the (K902) O2 Downstream Return circuit for a short to ground, open, or short to voltage. If OK, 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) .
5) O2 SENSOR
If there are no possible causes remaining, view repair.

Repair
1. Replace the O2 Sensor
2. Perform the POWERTRAIN VERIFICATION TEST. (Refer to STANDARD PROCEDURE - POWERTRAIN VERIFICATION TEST) .