Diagnostic Test

O2 SENSOR ABOVE 3.99 VOLTS
NOTE: When only one O2 Sensor is shorted to voltage, the scan tool will display all O2 Sensor voltage readings at approximately 5.0 volts. When diagnosing this DTC, only diagnose the O2 Sensor that set the DTC.
1. Start the engine.
2. Allow the engine to reach normal operating temperature.
3. With a scan tool, read the 2/1 O2 Sensor voltage.
Q: Is the voltage above 3.99 volts?

Yes :
- Go To 2
No :
- Refer to the INTERMITTENT CONDITION DIAGNOSTIC PROCEDURE .
- Perform the POWERTRAIN VERIFICATION TEST .
(K43) O2 2/1 SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE

Fig 1: Checking O2 Signal Circuit Shorted To Battery Voltage
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
1. Start the engine and allow the engine to idle.
2. Disconnect the 2/1 O2 Sensor harness connector.
3. Measure the voltage on the (K43) O2 Sensor 2/1 Signal circuit in the 2/1 O2 Sensor harness connector.
  NOTE: Measure the voltage in reference to ground, not the (K902) O2 Return Upstream circuit.
Q: Is the voltage above 0 volts?

Yes :
- Repair the short to battery voltage in the (K43) O2 Sensor 2/1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST .
No :
- Go To 3
(K902) O2 RETURN UPSTREAM CIRCUIT SHORTED TO BATTERY VOLTAGE

Fig 2: Identifying Oxygen Sensor Connector Terminals
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
1. Turn the ignition off.
2. Disconnect the C1 PCM harness connector.
3. Ignition on, engine not running.
4. Measure the voltage on the (K902) O2 Return Upstream circuit in the 2/1 O2 Sensor harness connector.
Q: Is there any voltage present?

Yes :
- Repair the short to battery voltage in the (K902) O2 Return Upstream circuit.
- Perform the POWERTRAIN VERIFICATION TEST .
No :
- Go To 4
O2 SENSOR

Fig 3: Identifying O2 Sensor Connector Terminals
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
1. Turn the ignition off.
2. Connect the C1 PCM harness connector.
3. Connect a jumper wire between the (K43) O2 2/1 Signal circuit and the (K902) O2 Return Upstream circuit in the O2 Sensor harness connector.
4. Ignition on, engine not running.
5. With a scan tool, monitor the 2/1 O2 Sensor voltage.
Q: Is the voltage between 2.3 and 2.7 volts with the jumper wire in place?

Yes :
- Replace the O2 Sensor.
- Perform the POWERTRAIN VERIFICATION TEST .
No :
- Go To 5
  NOTE: Remove the jumper wire before continuing.
(K43) O2 2/1 SIGNAL CIRCUIT OPEN

Fig 4: Checking O2 2/1 Signal Circuit Open
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
1. Turn the ignition off.
2. Disconnect the C1 and C2 PCM harness connectors.
  CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.
3. Measure the resistance of the (K43) O2 2/1 Signal circuit from the 2/1 O2 Sensor harness connector to the appropriate terminal of special tool #8815.
Q: Is the resistance below 5.0 ohms?

Yes :
- Go To 6
No :
- Repair the open in the (K43) O2 2/1 Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST .
(K902) O2 RETURN UPSTREAM CIRCUIT OPEN

Fig 5: Checking O2 Return Upstream Circuit Open
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
1. Measure the resistance of the (K902) O2 Return Upstream circuit from the O2 Sensor harness connector to the appropriate terminal of special tool #8815.
Q: Is the resistance below 5.0 ohms?

Yes :
- Go To 7
No :
- Repair the open in the (K902) O2 Return Upstream circuit.
- Perform the POWERTRAIN VERIFICATION TEST .
PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
1. Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
Q: Were there any problems found?

Yes :
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST .
No :
- Replace and program the Powertrain Control Module per Service Information.
- Perform the POWERTRAIN VERIFICATION TEST .