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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1375 (Engine Controls And Fuel - 6.6L - DTC P02E8 To DTC P1247) >> DTC P0401 or P0402 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT:
  • Perform the Circuit System Verification before proceeding with Circuit/System Testing.
  • Always replace the EGR valve or EGR cooler gaskets when removal or replacement of the components are necessary.
  1. Engine running at idle, ECT parameter must be greater than 80°C (176°F). Perform the following:
    1. Maintain engine speed at idle.
    2. With a scan tool, command the EGR solenoid to 0 percent and record the Mass Air Flow g/s parameter.
    3. With a scan tool, command the EGR solenoid to 40 percent while observing the actual EGR Position and the Mass Air Flow parameters. Record the Mass Air Flow g/s parameter. The Mass Air Flow g/s parameter should decrease by 15 g/s or more.
    • If the Mass Air Flow parameter does not decrease by 15 g/s or more, inspect the EGR cooler and the EGR valve passages for a restriction.
  2. Ignition OFF, inspect for the following:
    • The exhaust system for leaks, restrictions, or for modification of the original equipment manufacture (OEM) part
    • For a restriction in the air cleaner and the air intake ducts.
    • For a restriction in the turbocharger charge air cooler (CAC) system.
    • For a restriction in the intake manifold.
  3. Test the air induction system for air leaks between the MAF sensor and the turbocharger. Perform the Induction System Smoke Test. Refer to Charge Air Cooler Diagnosis (Induction System Smoke Test) , Charge Air Cooler Diagnosis (Full System Air Leak Test) or Charge Air Cooler Diagnosis (Charge Air Cooler Air Leak Test) .
  4. Test the charge air cooler system for leaks. Perform the Full System Air Leak Test. Refer to Charge Air Cooler Diagnosis (Induction System Smoke Test) , Charge Air Cooler Diagnosis (Full System Air Leak Test) or Charge Air Cooler Diagnosis (Charge Air Cooler Air Leak Test) .
  5. If the air induction, charge air cooler (CAC), and mass air flow test normal, operate the vehicle within the Conditions for Running the DTC. If the DTC resets, perform the Component Testing.
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