Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSPONTIAC2008GRAND PRIX V6-3.8LREPAIR AND DIAGNOSISENGINE, COOLING AND EXHAUSTEXHAUST SYSTEMTESTING AND INSPECTIONSYMPTOM RELATED DIAGNOSTIC PROCEDURESRESTRICTED EXHAUST
2008 Pontiac Grand Prix V6-3.8L
Restricted Exhaust
2008 Pontiac Grand Prix V6-3.8LSECTION Restricted Exhaust
Restricted Exhaust
Diagnostic Aids
For dual exhaust systems a quick check of exhaust flow will help determine which side of the exhaust system is restricted. The side that has less exhaust flow is the side that will be suspect, and the diagnosis should begin there.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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 Exhaust Back Pressure Gage.
Removing the heated oxygen sensor (HO2S) may set a DTC. When finishing this diagnostic table, be sure to clear all codes.
5. This step will isolate the catalytic converter from the remainder of the exhaust system.
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.
9. Confirming that the condition has been fixed is essential. If the symptom still exists, proceed to Step 2 and repeat the diagnostic procedure.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.