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: 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 for 90 seconds, Measure for a resistance of less than 5 ohms on each low reference circuit between terminals B and ground.
    • If the resistance is 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 harness connector X1 at the ECM.
  4. Test for less than 5 ohms on each of the following signal circuits:
    • ECM X1 signal circuit terminal 69 to EGT sensor 1 terminal A
    • ECM X1 signal circuit terminal 93 to EGT sensor 2 terminal A
    • If the resistance is greater than the specified range, repair the open/high resistance on the affected circuit.
  5. 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.