security light stays on while driving

1994 CADILLAC DEVILLE
132,000 MILES • 4.9L • V8 • FWD • AUTOMATIC
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KINGDOMBUILDER
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Car starts okay and alarm system works okay but the dash security light stays on while driving. I have located the Theft deterrent and Pass-key Decoder module in trunk behind back seat and they appear okay but see that there is also a Relay Center comprised of 11 identical relays and am thinking one of these relays is bad but I do not know which one and I need a diagram of which of these relays pertains to the alarm system so I can replace it and see if that eliminates my problem. I do not know out to test relays and have no test equipment so I need to know what relay is involved with the alarm system. Or, what do you suggest may be my problem?
May 15, 2014 at 10:39 AM
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HMAC300
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try another key firstif you have one the diode may be shot on the one you use. see pic for location
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May 15, 2014 at 12:47 PM
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KINGDOMBUILDER
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No change with 2nd key. All the relays in the trunk are the same type relay and I would like to know if its okay to have the engine running while I pull each relay out and replace.with a new one as the diagram doesn't appear to match up exactly with the trunk relay center in my car?
May 16, 2014 at 7:28 AM
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HMAC300
  • ✓ASE Certified Mechanic
  • 48,601 POSTS
  • ASE Certified Mechanic
just replace it with a like relay your inside cover may also have marked which relay is which. And yes you can do it with engine running. you probably are going to have to have the car scanned for the anti theft problem though.
May 16, 2014 at 8:07 AM
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