Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1999 Chevrolet Cutaway 7.4 JFACTORY OEM SERVICE PROCEDURE
Diagnostic Procedure
- Perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK in AIR BAG RESTRAINT SYSTEM article in RESTRAINTS. Go to next step.
- Ensure scan tool is functioning properly. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL INOPERATIVE/DOES NOT COMMUNICATE WITH COMPONENTS .
- Inspect for proper connection/terminal tension of scan tool to DLC terminal No. 9. See Figure . If there is no fault with connector, go to next step. If there is any fault with connector, repair and perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK in AIR BAG RESTRAINT SYSTEM article in RESTRAINTS.
- Carefully disconnect SDM. Check for poor connection/terminal tension at SDM terminal No. 5. See Figure . If there is no fault with connector, go to next step. If there is any fault with connector, repair and perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK in AIR BAG RESTRAINT SYSTEM article in RESTRAINTS.
- Test for an open in 800 circuit wire between DLC and SDM connector. See Figure . If there is no fault with the wire, go to next step. If there is any fault with the wire, repair and perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK in AIR BAG RESTRAINT SYSTEM article in RESTRAINTS.
- Test for a short to ground in 800 circuit wire between DLC and SDM connector. See Figure . If there is no fault with the wire, go to next step. If there is any fault with the wire, repair and perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK in AIR BAG RESTRAINT SYSTEM article in RESTRAINTS.
- Test for a short to voltage in 800 circuit between DLC and SDM connector. See Figure . If there is no fault with the wire, go to next step. If there is any fault with the wire, repair and perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK in AIR BAG RESTRAINT SYSTEM article in RESTRAINTS.
- Turn ignition switch to OFF. Replace Inflatable Restraint Sensing and Diagnostic Module. See SENSING & DIAGNOSTIC MODULE (SDM) in AIR BAG RESTRAINT SYSTEM article in RESTRAINTS. Perform SIR diagnostic system check. See SIR DIAGNOSTIC SYSTEM CHECK in AIR BAG RESTRAINT SYSTEM article in RESTRAINTS.
Factory Service Tools
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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.
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