Diagnostic Procedures

2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8SECTION Diagnostic Procedures
WARNING: This page is about a different variant/trim than selected.
  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command SERVICE THROTTLE SOON light on and off. If SERVICE THROTTLE SOON light illuminates, go to next step. If SERVICE THROTTLE SOON light does not illuminate, go to step  4.
  3. Problem is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS . If any additional DTCs are set, perform appropriate DTC test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  4. Turn ignition off. Disconnect PCM harness connector C3. See Figure or Figure . Turn ignition on. If SERVICE THROTTLE SOON light does not illuminate, go to next step. If SERVICE THROTTLE SOON light illuminates, go to step  7.
  5. Connect a fused jumper wire between ground and PCM harness connector C3 terminal D11 (White/Black wire). If SERVICE THROTTLE SOON light illuminates, go to next step. If SERVICE THROTTLE SOON light does not illuminate, go to step  8.
  6. Turn ignition off. Check for poor connections at PCM harness connector. Repair as necessary. After repairs, go to step  10. If connections are okay, go to step  9.
  7. Turn ignition off. Repair short to ground in White/Black wire between SERVICE THROTTLE SOON light and PCM harness connector C3 terminal D11. After repairs, go to step  10.
  8. Turn ignition off. Check for open in Pink wire between SERVICE THROTTLE SOON light and instrument panel fuse/relay block. Check for faulty bulb. Check for open or short to battery voltage in White/Black wire between SERVICE THROTTLE SOON light and PCM harness connector C3 terminal D11. Repair as necessary. After repairs, go to step  10.
  9. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  10. Turn ignition on, with engine off. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and then enter DTC P1654. Operate vehicle within the conditions for setting DTC. See CODE ENABLE CRITERIA . If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, go to step  2.
  11. Using scan tool, check for DTCs. If any undiagnosed DTCs are set, perform appropriate DTC test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are set, system is okay.
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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.