Circuit/System Testing

WARNING: This page is about a different car, the 2006 Pontiac Montana SV6, 2006 Chevrolet Uplander, and 2006 Buick Terraza. However, it is still accessible from the selected car via links, so may be relevant.

Test the MAP sensor for being shifted, stuck, skewed and for correct vacuum supply. Refer to Manifold Absolute Pressure (MAP) Sensor Diagnosis .
Inspect for a vacuum leak between the EGR valve and the intake manifold.
Inspect the exhaust system for leaks, restrictions and for modification of OEM parts.
Remove the EGR valve and inspect for the following:
- Cracks
- Heat distress
- Pintle for corrosion
- EGR valve passages for restriction
- EGR passage in the intake manifold for carbon buildup, casting flash or other restriction
  - If a restriction is identified, refer to Exhaust Gas Recirculation (EGR) System Cleaning .
  - If a condition with the EGR valve is identified, replace the EGR valve.
Inspect the engine for correct valve timing and lift or for other conditions that might affect engine vacuum source. Refer to Symptoms - Engine Mechanical .