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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G3500, VAN PASSENGER EXTENDEDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 10 (ENGINE CONTROL SYSTEM & FUEL SYSTEM - 6.6L (LMM) - DTC P0016 TO DTC P0299)DTC P0101CIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G3500, Van Passenger Extended

Circuit/System Testing

2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Circuit/System Testing
WARNING: This page is about a different variant/trim than selected.
IMPORTANT:
  • You must perform the Circuit/System Verification before proceeding with the circuit/system testing.
  • You must perform the Repair Verification after completing the Circuit/System Testing.
  1. Verify the integrity of the entire air induction system by inspecting for the following conditions:
    • A loose or disconnected charge air cooler hose or pipe
    • A restricted or collapsed air intake duct
    • A misaligned or damaged air intake duct
    • A dirty or deteriorating air filter element
    • Any objects blocking the air inlet probe of the MAF/IAT sensor
    • Any contamination or debris on the sensing elements in the probe of the MAF/IAT sensor
    • A cracked or damaged MAF sensor housing
    • Any water intrusion in the induction system
    • Any snow or ice build-up at the air cleaner or MAF Sensor
    • Any snow, ice build-up, or coking at the MAP sensor
    • An intake manifold leak
    • A MAP sensor seal that is missing or damaged
    • An Intake Manifold Resonator with a leaking seal, or a cracked or broken housing
  2. Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
  3. Ignition OFF for 90 seconds, test for less than 5 ohms between the MAF low reference circuit terminal 2 and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  4. Ignition OFF, test for less than 5 ohms between the IAT sensor low reference circuit terminal 4 and ground.
    • If greater than the specified range, test the IAT sensor low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  5. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 3 and ground.
    • If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  6. Ignition ON, test for 4.8-5.2 volts between the signal circuit terminal 1 and ground.
    • If less than the specified range, test the MAF signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
    • If greater than the specified range, test the MAF signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  7. Test the charge air cooler system for leaks. Refer to Charge Air Cooler Diagnosis (Full System Air Leak Test) or Charge Air Cooler Diagnosis (Charge Air Cooler Air Leak Test) or Charge Air Cooler Diagnosis (Induction System Smoke Test) .
  8. Remove the Intake Manifold Tube. Refer to Intake Manifold Tube Replacement (LMM) .
  9. Visually inspect the EGR valve and verify the valve is in the closed position.
    • If the EGR valve is not in the closed position, replace the EGR valve.
  10. Ignition OFF, connect the red lead of the J 38522  to the signal circuit terminal A at the MAF/IAT sensor harness connector. Connect the battery voltage supply to B+, and ground the black lead.
  11. Set the J 38522  signal circuit to 5 volts, the frequency to 5K, and the Duty Cycle to Normal.
  12. Engine idling, observe the scan tool MAP Sensor parameter. The scan tool MAF Sensor parameter should be between 4.950-5.025 Hz.
    • If the MAF Sensor parameter is not within the specified range, replace the ECM.
RENDER: 1.0x

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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.