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
1. Refer to the recorded DTCs.
  Are there any Upstream or Downstream O2 Sensor signal or heater circuit DTCs present?
  
  Yes
  - Perform the applicable O2 Sensor diagnostic procedure(s) before continuing with this diagnostic procedure. Refer to DTC INDEX (1 OF 2) and/or DTC INDEX (2 OF 2) .
  No
  - Go To 3
VISUALLY INSPECT CATALYTIC CONVERTER
1. Inspect the Catalytic Converter inlet and outlet for the following damage:
  - Physical damage (dents or holes) to the Catalytic Converter.
  - Catalytic Converter leaking.
  - Catalytic Converter internally broken.
  - Severe discoloration caused by overheating the Catalytic Converter.
  Were any problems found?
  
  Yes
  - Repair the condition that may have caused the failure and replace the Catalytic Converter in accordance with the Service Information. Refer to CONVERTER, CATALYTIC, REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 4
CHECK THE EXHAUST SYSTEM FOR LEAKS
NOTE:
A leak in the exhaust system, especially before the Catalytic Converter can cause an the Upstream O2 Sensor to drift out of range or not switch properly and fail the Catalyst Monitor. Depending on the location of the leak, even a very small exhaust leak can cause a failure.
1. Perform the CHECKING THE EXHAUST SYSTEM FOR LEAKS test procedure. Refer to CHECKING THE EXHAUST SYSTEM FOR LEAKS .
  Were any exhaust leaks found?
  
  Yes
  - Repair or replace the leaking exhaust components as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 5
CHECK FOR AN ENGINE MECHANICAL ISSUE
NOTE:
An engine that has a mechanical failure causing it to consume oil, coolant or excessive fuel can foul the Upstream O2 Sensor since it is not protected by the catalyst.
1. Check the exhaust for excessive smoke caused by an internal problem in the engine. Verify that the Upstream O2 Sensor is not fouled due to a mechanical engine failure.
  Is there an engine mechanical condition present?
  
  Yes
  - Repair the engine mechanical condition as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 6
CHECK FOR AN AGING UPSTREAM O2 SENSOR AND NEW DOWNSTREAM O2 SENSOR
NOTE:
A new Downstream O2 Sensor paired with an aging Upstream O2 Sensor may cause the DTC to set.
1. Review the vehicles repair history.
  Has the Downstream O2 Sensor been replaced recently without replacing the Upstream O2 Sensor?
  
  Yes
  - Replace the Upstream 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 .
  No
  - Go To 7
REPLACE THE CATALYTIC CONVERTER
If there are no possible causes remaining, view repair.

Repair
- Replace the Catalytic Converter in accordance with the Service Information. Refer to CONVERTER, CATALYTIC, REMOVAL AND INSTALLATION .
- Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .