Diagnostic Procedure

1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Procedure
WARNING: This page is about a different car, the 2002 GMC Savana and 2002 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
  1. If SIR Diagnostic System Check has been performed, go to next step. If SIR Diagnostic System Check has not been performed, go to SIR DIAGNOSTIC SYSTEM CHECKΒ .
  2. Using scan tool, verify PCM is programmed with correct VIN. If VIN is not correct, go to next step. If VIN is correct, go to step Β 4.
  3. Using scan tool, program PCM with correct VIN. Go to step Β 5.
  4. Replace SDM. See SENSING & DIAGNOSTIC MODULE (SDM)Β  under REMOVAL & INSTALLATION. Go to next step.
  5. Reconnect all SIR components. Ensure that all components are properly mounted. Go to SIR DIAGNOSTIC SYSTEM CHECKΒ .
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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.