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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1076 (ENGINE CONTROLS AND FUEL - 6.6L (LMM) - DTC P154B TO DTC P2693)DTC P2459CIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6

Circuit/System Testing

2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Circuit/System Testing
WARNING: This page is about a different car, the 2007 GMC Sierra, 2007 GMC Cab & Chassis Sierra, 2007 Chevrolet Silverado, and 2007 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
    IMPORTANT: Perform the Repair Verification after completing the Circuit/System Testing.
  1. Visually inspect the exhaust differential pressure system for any of the following conditions:
    • Modifications
    • Damaged components
    • Loose or improperly installed components
    • Improperly routed differential pressure lines-The exhaust differential pressure line should have a continuous downward gradient without any sharp bends or kinks from the sensor to the DPF.

  2. Remove and visually inspect the flexible part of the exhaust differential pressure lines for internal restrictions.
    • If a condition is found, replace the exhaust differential pressure lines.
  3. Verify that restrictions do not exist in the exhaust particulate filter. Refer to Restricted Exhaust .
    • If a condition is found, replace the particulate filter.
  4. Ignition ON, observe the scan tool EGR Position Sensor and Desired EGR Position parameters while commanding the EGR solenoid to 20 percent and 0 percent. The values should remain equal to or less than 3 percent.
    • If greater than the specified range, replace the EGR valve.
  5. Test the EGR valve gaskets and cooler gaskets for leaks. Apply a soap solution to the gaskets while commanding the TC Vane Pos. Ctrl. Solenoid ON, and inspect for excessive air bubbles at the EGR valve gaskets and cooler gaskets.
    • If an air leak is found, replace the EGR valve gaskets or EGR cooler gasket.
  6. Test the charge air cooler (CAC) for leaks. Refer to Charge Air Cooler Diagnosis (Charge Air Cooler Air Leak Test) or Charge Air Cooler Diagnosis (Full System Air Leak Test) .
  7. Test the fuel system for leaking fuel injectors, high fuel pressures, or high fuel injector flow rates. Refer to Fuel Injector Balance Test with Tech 2 .
  8. Ignition OFF, disconnect the harness connector at the exhaust differential pressure sensor.
  9. Ignition OFF for 90 seconds, test for less than 5 ohms of resistance between the low reference circuit terminal 1 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.
  10. Disconnect the harness connector X1 at the ECM.
  11. Test for less than 5 ohms of resistance on the differential pressure sensor circuits between the following terminals:
    • ECM X1 5-volt reference circuit terminal 14 to exhaust differential pressure sensor terminal 3.
    • ECM X1 signal circuit terminal 43 to exhaust differential pressure sensor terminal 2.
    • If greater than the specified range, repair the affected circuit for an open/high resistance.
  12. If all circuits and engine control components test normal, test or replace the exhaust differential pressure sensor.
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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.