Diagnostic Test

READ AND RECORD DTCS AND ENVIRONMENTAL DATA - ERASE DTCS AND CHECK FOR THE DTC TO RETURN
1. With the scan tool, read DTCs in all Electronic Control Units (ECUs) and record on the repair order.
2. For future reference, with the scan tool, run and save a vehicle Scan Report and all related recorded data.
3. With the scan tool, erase all DTCs.
4. Turn the ignition off for a minimum of 10.0 seconds.
5. Turn the ignition on.
6. Using the When Monitored and Set Conditions above and recorded data, operate the vehicle in the conditions that set the DTC.
7. With the scan tool, read DTCs.
Did the DTC return?

Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
CHECK FOR OTHER DTCS
NOTE:
Check for contaminants that may have damaged an O2 Sensor: contaminated fuel, unapproved silicone, oil or coolant in the exhaust system.
1. Refer to the recorded DTCs.
  Are there any O2 Sensor DTCs active or pending?
  
  Yes
  - Perform the applicable diagnostic procedure(s). Refer to 3.6L (GPEC 2A) - DIAGNOSTIC CODE INDEX .
  No
  - Go To 3
CHECK THE EXHAUST SYSTEM FOR LEAKS
1. Perform the CHECKING THE EXHAUST SYSTEM FOR LEAKS test procedure. Refer to CHECKING THE EXHAUST SYSTEM FOR LEAKS .
  NOTE:
  An exhaust leak of any size at or upstream of the Downstream O2 Sensor can cause this DTC to set. It is critical to thoroughly inspect and repair any leak before continuing on and replacing an O2 Sensor.
  
  Were any problems found?
  
  Yes
  - Repair as necessary in accordance with the Service Information.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 4
CHECK THE UPSTREAM O2 SENSOR WIRING FOR AN OPEN OR SHORT TO GROUND
NOTE:
The Downstream Fuel Trim Diagnostic will fault based on the trim adjustment to the Upstream O2 Sensor being beyond a calibrated threshold. Therefore, if there are no exhaust system leaks, it is more likely that the Upstream O2 Sensor is the cause of any Downstream Fuel Trim System Rich/Lean fault than the Downstream O2 Sensor. For this reason the Upstream O2 Sensor and wiring should be diagnosed before the Downstream O2 Sensor.
1. Disconnect the Upstream O2 Sensor harness connector.
2. 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.
3. Connect the (special tool #10436, Adapter, GPEC Diagnostic).
4. Check the Upstream O2 Sensor circuits;
  - for a short to ground in the wiring between the O2 Sensor harness connector and the PCM C2 harness connector.
  - for an open or high resistance in the wiring between the O2 Sensor harness connector and the PCM C2 harness connector.
  Were any problems found?
  
  Yes
  - Repair the wiring for an open or short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 5
REPLACE THE UPSTREAM O2 SENSOR AND RETEST FOR DTCS
1. Verify that there is good pin to terminal contact in the O2 Sensor 2/1 and Powertrain Control Module connectors. Replace the component in accordance with the Service Information. Refer to ENGINE SENSORS, REMOVAL AND INSTALLATION .
2. Connect the component and Electronic Control Unit (ECU) harness connectors.
3. Turn the ignition on.
4. With the scan tool, erase DTCs.
5. Using the Environmental Data or When Monitored Conditions above, operate the vehicle within the conditions that set the DTC.
6. With the scan tool, read DTCs.
Did the DTC return?

Yes
- Go To 6
No
- Replacing the faulty component repaired the fault.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE DOWNSTREAM O2 SENSOR WIRING FOR AN OPEN OR SHORT TO GROUND
1. Disconnect the Downstream O2 Sensor harness connector.
2. 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.
3. Connect the (special tool #10436, Adapter, GPEC Diagnostic).
4. Check the Downstream O2 Sensor circuits;
  - for a short to ground in the wiring between the O2 Sensor harness connector and the PCM C2 harness connector.
  - for an open or high resistance in the wiring between the O2 Sensor harness connector and the PCM C2 harness connector.
  Were any problems found?
  
  Yes
  - Repair the wiring for an open or short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 7
REPLACE THE DOWNSTREAM O2 SENSOR AND RETEST FOR DTCS
1. Verify that there is good pin to terminal contact in the O2 Sensor 2/2 and Powertrain Control Module connectors. Replace the component in accordance with the Service Information. Refer to ENGINE SENSORS, REMOVAL AND INSTALLATION .
2. Connect the component and Electronic Control Unit (ECU) harness connectors.
3. Turn the ignition on.
4. With the scan tool, erase DTCs.
5. Using the Environmental Data or When Monitored Conditions above, operate the vehicle within the conditions that set the DTC.
6. With the scan tool, read DTCs.
Did the DTC return?

Yes
- Go To 8
No
- Replacing the faulty component repaired the fault.
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK RELATED PCM AND COMPONENT CONNECTIONS
1. Perform any Service Bulletins that apply.
2. Disconnect all PCM harness connectors.
3. Disconnect all related in-line harness connections (if equipped).
4. Disconnect the related component harness connectors.
5. 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.
6. Reconnect all PCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
7. Reconnect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
8. Reconnect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
9. With the scan tool, erase DTCs.
10. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
11. With the scan tool, read DTCs.
  Did the DTC return?
  
  Yes
  - Replace and program the Powertrain Control Module (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
  - The wiring or poor connection problem has been repaired.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .