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 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.
    NOTE: Perform the Repair Verification after completing the Circuit/System Testing.
  1. Ignition OFF, disconnect both harness connectors at EGT sensor 1 and sensor 2.
  2. Ignition OFF and scan tool disconnected for 90 seconds, Measure for a resistance of less than 5 Ξ© on each low reference circuit between terminals B and ground.
    • If greater than the specified range, repair the open/high resistance on the affected circuit. If the circuit tests normal, replace the ECM.
  3. Ignition OFF, disconnect the X1 harness connector at the ECM.
  4. Test for less than 5 Ξ© between the signal circuit terminal A of the EGT sensor 1 and the corresponding terminal 69 X1 of the ECM.
    • If greater than the specified range, repair the open/high resistance in the circuit.
  5. Test for less than 5 Ξ© between the signal circuit terminal A of the EGT sensor 2 and the corresponding terminal 93 X1 of the ECM.
    • If greater than the specified range, repair the open/high resistance in the circuit.
  6. If all circuits test normal, test or replace the affected 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:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.