Cadillac Repair: Security Light 1993 DeVille, key decoder, intermittent fault


Question
QUESTION: My security light goes through the proper squence when starting the car but comes on while driving. Usually stays on for a while then might/might not go out. Does not effect the cars performance. Thanks
ANSWER: NO. You have an intermittent fault. Check the computer for diagnostic codes.

1. Ignition ON. Engine OFF.

2. Simultaneously push and hold the OFF and WARMER (^) buttons on the climate control panel and see if any LETTER/NUMBER codes appaer as HISTORY or CURRENT and let me know what they are in the EXACT order in which they display.

3. turn igntion OFF.

---------- FOLLOW-UP ----------

QUESTION: First thing this morning I tried what you asked. NOTHING. NO CODES.Drove to town and all was normal. On the way home SECURITY LIGHT came on and stayed on. As soon as I turned off the ignation I tried the off/warm buttons. NO CODES. Is there a control head/box I can ck for loose wires or perhaps get one off a junker to troubleshoot?

Answer
when your driving the vehicle, As soon as the security light comes on, Immediately check for codes while still driving and see what appaers.

Fault could be:

Faulty contacts in the ignition key lock cylinder.

Ignition key chip.

Theft deterrent controller.

Pass-key decoder module.

Try cleaning your ignition key.