Diagnostic Test

CHECK FOR AN ACTIVE CONDITION
1. Turn the ignition off.
2. Wait 8 minutes to allow the Oxygen (O2) Sensor to cool down.
3. Turn the ignition on.
4. With the scan tool, actuate the O2 Sensor 1/1 heater control.
5. With the scan tool, read the O2 Sensor 1/1 signal voltage for two minutes.
  Does the voltage stay above 4.5 volts?
  
  Yes
  - Go To 2
  No
  - Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
CHECK FOR OTHER DTCS
1. With the scan tool, read and record DTCs on the repair order.
  Are the O2 Sensor Heater Circuit Low or High DTCs active or pending?
  
  Yes
  - Perform the applicable diagnostic procedure(s). Refer to DTC INDEX (1 OF 2) and/or DTC INDEX (2 OF 2) .
  No
  - Go To 3

CHECK THE O2 SENSOR 1/1 HEATER ELEMENT RESISTANCE

Turn the ignition off.
Wait 8 minutes to allow the sensor to cool down.
Disconnect the O2 Sensor 1/1 harness connector.

Measure the resistance of the O2 Sensor 1/1 Heater Element across the O2 Sensor, between the O2 Heater Control terminal and the Heater ground terminal (component side).

NOTE:

It is best to measure the O2 Sensor 1/1 Heater Element resistance when the O2 Sensor temperature is about 25°C (77°F). The resistance will vary with temperature. If the O2 Sensor is significantly warmer than 25°C (77°F), use the table below to estimate what the resistance range should be. The MAXIMUM allowable resistance is 8.0 Ohms at 1000°C.

Celsius	Fahrenheit	Resistance Range
25°C	77°F	2.5 - 4.0 Ohms
50°C	112°F	2.55 - 4.1 Ohms
100°C	212°F	2.65 - 4.31 Ohms
150°C	302°F	2.75 - 4.52 Ohms

Is the O2 Sensor heater element resistance within the specified range?

Yes

Go To 4

Verify that there is good pin to terminal contact in the O2 Sensor and PCM harness connectors. If no problems are found, replace the O2 Sensor in accordance with the Service Information. Refer to ENGINE SENSORS, REMOVAL AND INSTALLATION .
Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

CHECK THE (K79) O2 SENSOR 1/1 HEATER CONTROL CIRCUIT FOR AN OPEN OR HIGH RESISTANCE
1. Disconnect the PCM C2 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 the GPEC Diagnostic Adaptor to perform the diagnosis.
2. Connect the (special tool #10436, Adapter, GPEC Diagnostic).
3. Measure the resistance of the (K79) O2 Sensor 1/1 Heater Control circuit between the Oxygen Sensor 1/1 harness connector and the GPEC Adaptor.
  Is the resistance below 2.0 Ohms?
  
  Yes
  - Go To 5
  No
  - Repair the (K79) O2 Sensor 1/1 Heater Control circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE O2 SENSOR GROUND CIRCUIT FOR AN OPEN OR HIGH RESISTANCE
1. Measure the resistance between ground and the O2 Sensor Ground circuit at the O2 Sensor 1/1 harness connector.
  Is the resistance below 2.0 Ohms?
  
  Yes
  - Go To 6
  No
  - Repair the O2 Sensor Ground circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK RELATED HARNESS CONNECTIONS
1. Disconnect all PCM harness connectors.
2. Disconnect all related in-line harness connections (if equipped).
3. Disconnect the related component harness connectors.
4. Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
  - Proper connector installation.
  - Damaged connector locks.
  - Corrosion.
  - Other signs of water intrusion.
  - Weather seal damage (if equipped).
  - Bent terminals.
  - Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
  - Terminals that have been pushed back into the connector cavity.
  - Check for spread terminals and verify proper terminal tension.
  Repair any conditions that are found.
5. Connect all PCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
6. Connect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
7. Connect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
8. With the scan tool, erase DTCs.
9. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
10. With the scan tool, read Transmission Control Module (TCM) DTCs and record on the repair order.
  Did the DTC return?
  
  Yes
  - Replace and program the PCM in accordance with the Service Information. Refer to MODULE, POWERTRAIN CONTROL (PCM), REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Repair the poor connections.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .