Diagnostic Test

1. Turn the ignition off.
   NOTE: Wait a minimum of 8 minutes to allow the O2 Sensor to cool down before continuing the test. Allow the O2 Sensor voltage to stabilize between 4.6 and 5.0 volts.
2. Ignition on, engine not running.
3. With a scan tool, actuate the O2 Heater Test.
4. With the scan tool, monitor 1/1 O2 Sensor voltage for at least 2 minutes.

Q: Does the voltage stay above 4.5 volts? 

Yes : 

• Go To 2

No : 

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

1. Turn the ignition off.
   NOTE: Allow the O2 sensor to cool down to room temperature.
2. Disconnect the O2 Sensor harness connector.
3. Measure the resistance of the O2 Heater Element across the 1/1 O2 Sensor connector between the O2 Heater Control terminal and the Heater ground terminal.
   NOTE: O2 Heater Element resistance values should be measured at 70°F (21.1°C). The resistance value will vary with different temperature values.

Q: Is the resistance of the O2 Sensor Heater Element between 2.0 and 30.0 ohms? 

Yes : 

• Go To 3

No : 

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

Fig 1: Checking O2 1/1 Heater Control Circuit Open

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

1. Disconnect the C2 PCM harness connector.
   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.
2. Measure the resistance of the (K99) O2 1/1 Heater Control circuit from the O2 harness connector to the appropriate terminal of special tool #8815.

Q: Is the resistance below 0.5 of an ohm? 

Yes : 

• Go To 4

No : 

• Repair the excessive resistance in the (K99) O2 1/1 Heater Control circuit.
• Perform the POWERTRAIN VERIFICATION TEST .

Fig 2: Identifying O2 Sensor Connector Terminals

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

1. Measure the resistance between ground and the (Z43) O2 1/1Heater ground circuit in the O2 Sensor harness connector.

Q: Is the resistance below 0.5 of an ohm? 

Yes : 

• Go To 5

No : 

• Repair the excessive resistance in the (Z43) O2 1/1 Heater ground circuit.
• Perform the POWERTRAIN VERIFICATION TEST .

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 .