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 Cadillac Seville STSFACTORY OEM SERVICE PROCEDURE
Data Link Communications Diagnostics System Check
- Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Attempt to establish communications with vehicle. If scan tool communicates with vehicle, go to next step. If scan tool does not communicate with vehicle, go to DATA LINK COMMUNICATIONS SYSTEM CHECK .
- Use scan tool to display DTCs. If any loss of class 2 serial data communications DTCs are set (DTCs will begin with "U"), perform appropriate test under DIAGNOSTIC TESTS. For DTC definitions, see BODY CONTROL SYSTEM DTC DEFINITIONS table under SELF-DIAGNOSTIC SYSTEM. If no class 2 loss of communication DTCs are set, system is okay at this time.
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.