Diagnostic Test

1. 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.
2. With a scan tool, read DTCs.

Q: Is the DTC active at this time? 

Yes : 

• Go To 2

No : 

• Refer to the INTERMITTENT CONDITION DIAGNOSTIC PROCEDURE .
• Perform the POWERTRAIN VERIFICATION TEST .

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

Q: Are there any exhaust leaks? 

Yes : 

• Repair or replace the leaking exhaust parts as necessary.
• Perform the POWERTRAIN VERIFICATION TEST .

No : 

• Go To 3

Fig 1: Checking O2 Signal Circuit Shorted To Battery Voltage

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

1. Turn the ignition off
2. Disconnect the 1/2 O2 Sensor harness connector.
3. Ignition on, engine not running.
4. Measure the voltage on the (K141) O2 1/2 Signal circuit in the O2 Sensor harness connector.

Q: Is the voltage approximately 5.0 volts? 

Yes : 

• Go To 4

No : 

• 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.
• Perform the POWERTRAIN VERIFICATION TEST .

Fig 2: Identifying Oxygen Sensor Connector Terminals

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

1. Measure the voltage on the (K904) O2 Return Downstream circuit in the 1/2 O2 Sensor harness connector.

Q: Is the voltage at 2.5 volts? 

Yes : 

• Go To 5

No : 

• Check the (K904) O2 Return Downstream circuit for a short to ground, open, or short to voltage. If OK, replace and program the Powertrain Control Module per Service Information.
• Perform the POWERTRAIN VERIFICATION TEST .

Q: If there are no possible causes remaining, view repair. 

Repair : 

• Replace the O2 Sensor
• Perform the POWERTRAIN VERIFICATION TEST .