Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 4. The exhaust system has very low back pressure under normal conditions. If the exhaust system is restricted, a significant increase in the exhaust pressure is noticed on the J 35314-A. 

   Removing the AIR check valve or HO2S sensor may set a DTC. When finishing this diagnostic table, be sure to clear all codes.

2. 5. This step will isolate the catalytic converter from the remainder of the exhaust system.
3. 8. Confirming that the condition has been fixed is essential. If the symptom still exists and the vehicle has a dual exhaust system, proceed to Step 2 and repeat diagnostic procedure on the opposite exhaust pipe.

Fig 1: Restricted Exhaust Diagnosis (Steps 1-5)

Courtesy of GENERAL MOTORS CORP.

Fig 2: Restricted Exhaust Diagnosis (Steps 6-8)

Courtesy of GENERAL MOTORS CORP.