Diagnostic Test

O2 SENSOR HEATER OPERATION
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 at 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 2/2 O2 Sensor voltage for at least 2 minutes.
Q: Does the O2 Sensor voltage stay above 4.5 volts?

Yes :
- Go To 2
No :
- Refer to the INTERMITTENT CONDITION Diagnostic Procedure .
- Perform the POWERTRAIN VERIFICATION TEST .
O2 HEATER ELEMENT
1. Turn the ignition off.
  NOTE: Allow the O2 Sensor to cool down to room temperature.
2. Disconnect the 2/2 O2 Sensor harness connector.
3. Measure the resistance across the O2 Sensor Heater element, between the O2 Heater Control terminal and the O2 Heater ground terminal in the component connector.
  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 O2 Sensor Heater Element resistance between 2.0 and 30.0 ohms?

Yes :
- Go To 3
No :
- Replace the O2 Sensor.
- Perform the POWERTRAIN VERIFICATION TEST .
O2 SENSOR

Fig 1: Identifying Heated Oxygen Sensor Connector Terminals
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
1. Ignition on, engine not running.
2. With a scan tool, actuate the O2 Heater Test with the O2 Sensor harness connector still disconnected.
3. Using a 12-volt test light connected to ground, probe the (K399) O2 2/2 Heater Control circuit in the O2 Sensor harness connector.
Q: Does the test light illuminate brightly and flash on and off during the actuation?

Yes :
- Replace the O2 Sensor.
- Perform the POWERTRAIN VERIFICATION TEST .
No :
- Go To 4
(K399) O2 2/2 HEATER CONTROL CIRCUIT SHORTED TO GROUND

Fig 2: Checking O2 1/1 Heater Control Circuit Shorted To Ground
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
1. Turn the ignition off.
2. Disconnect the C3 PCM harness connector.
3. Measure the resistance between ground and the (K399) O2 2/2 Heater Control circuit in the O2 Sensor harness connector.
Q: Is the resistance below 5.0 ohms?

Yes :
- Repair the short to ground in the (K399) O2 2/2 Sensor Heater Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST .
No :
- Go To 5
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 .