Diagnostic Procedure

1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Procedure
WARNING: This page is about a different car, the 2002 Saturn Vue. 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 CHECK .
  2. Turn ignition off. If head impact air bag deployment has occurred, go to next step. If frontal air bag deployment has occurred, go to step  4. If no deployment has occurred, go to step  5.
  3. Replace head impact air bag and Side Impact Sensor (SIS) on side of deployment. See AIR BAG MODULES  and SIDE IMPACT SENSOR (SIS)  under REMOVAL & INSTALLATION. Replace SDM. See SENSING & DIAGNOSTIC MODULE (SDM)  under REMOVAL & INSTALLATION. Go to step  5.
  4. Replace SIR coil assembly, driver-side and passenger-side air bag modules. See AIR BAG MODULES  and SIR COIL ASSEMBLY  under REMOVAL & INSTALLATION. Replace SDM. See SENSING & DIAGNOSTIC MODULE (SDM)  under REMOVAL & INSTALLATION. Go to next step.
  5. Inspect front of vehicle and undercarriage for signs of impact. If impact has occurred, repair applicable damage. See POST-COLLISION INSPECTION . Go to next step. If no impact has occurred, go to next step.
  6. Replace SDM. See SENSING & DIAGNOSTIC MODULE (SDM)  under REMOVAL & INSTALLATION. Go to next step.
  7. Reconnect all SIR components. Ensure that all components are properly mounted. Using scan tool, Using scan tool, clear all SIR DTC's. Go to SIR DIAGNOSTIC SYSTEM CHECK .
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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.