This case study took an unexpected turn that could only happen in certain areas of the country. The vehicle in this case study is an 1992 Cadillac Eldorado. When this car was dropped off, I was told that it was a no start caused by the anti-theft system. The first step I took on this one was to confirm the no start. I turned the key to the run position and nothing happened besides power being cut to unnecessary devices. Next step on my list was to check for codes, none present. So I decided to print out the starting system electrical diagrams. The first image is the diagram I used.

Power goes from the battery, to fuse, to ignition switch, to the starter enable relay that is controlled by the pass-key decoder module. Then the power goes from the starter enable relay, thru the transmission position switch, to the the starter. I diagnose electrical problems 3 ways; #1: by finding the easiest testing points, #2: by testing at points in which multiple tests can be performed, and #3: by going to common failure points.

After looking at the wire diagram on the starting system, I choose to use #2. I saw the starter enable relay as a great place to check for power after the ignition switch, check to see if the anti-theft system was enabling the starter, and I was able to jump power to see if the starter would engage. Testing from here let me divide the circuit into 3 smaller circuits and to also check for the three things this circuit used. Power, ground through the starter and the anti-theft enable. I figured I would also be using my 1st way to diagnose but when I found out that the starter enable relay was under the driver side carpet I knew it wasn’t my 1st way but it was my 3rd way. How many corroded wires and bad grounds have you found under carpet? I sure have found my share.

As I started pulling trim off and started pulling back the carpet I ran in to something not everyone gets to see. This car was just pulled in out 0*F weather and the carpet was completely frozen rock hard. I had to pry back the carpet far enough to get to the relay and connector. I then check the relay for power at terminal 1 and 2. Then I checked to see if the pass-key decoder module was actually trying to ground out the relay, which it was. I finally jumped power from terminal 1 to terminal 4 which engaged the starter. Now I know that the power supply circuit, anti-theft system, and the rest of the starter circuit are all good besides the relay itself all at one location. The problem with this car was that the relay filled with water from the sunroof that was missing and then it froze solid. You think they see that in Arizona! The relay still worked after I thawed it but it still got a new one and off it went.

Leave any questions or comments below. Thank you.

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Comments (21)

  1. I have a 92 eldorado n my auto theft system came on it won’t start n it also has not been driven or started up since july of 2012 n I dont know what to do I need help bad please email me

    • Travis Dewitz

      You need to have the system diagnosed by testing. Start with your powers and make sure your chipped key is good and that the signal is making it to the theft module.

  2. Erick Wingfield

    I had the same problem but it happened in a day car was fine up until yesterday came out the store wouldnt start sat for a while then it started right up drove it home turned it off tried to start it wouldnt start was haring clicking from my side along the seat when i was trying to start it so i put up the carpet to see where the clicking was coming from found the relay didnt know what it was can inside found your site low and behold you had a car on there same year as mine 92 cad i eldorado its been cold out here like 10 and 20s Thanks for the help

  3. I can’t find the ignition relay anywhere for purchase. Where did you get the replacement? autozone doesn’t have it nor does any online sites I could find. Please help, I’m 99% sure this is the problem with my 92 eldorado.

    • Travis Dewitz

      I had to search hard myself for that. Can you get a number off the old relay?

  4. Matt Eggleston

    I did find it. The original part number is 14100455 It has since been replaced by a new part number, which I don”t have offhand. I replaced it but it wasn’t the problem. I had a wiring harness come loose and was resting on the exhaust pipe, it melted and also the insulation around a bunch of wires. Things were shorting to different circuits and blowing various fuses. Cost me $550 all labor to fix it. Could have been much more. Got lucky. On the relay: It’s a multi purpose relay used in many cars. Here’s some pics and links

  5. kiara

    I have a 1997 Cadillac Eldorado. I had a used computer put on it,& every since then it been reading “Theft System Problem,Car May Not Restart”. It did that for 3 weeks & it finally did not start yesterday. Horn wont blow. Please help me

    • Travis Dewitz

      Start testing the horn circuit if both problems happened at the same time.

  6. i had cadillac el dorado 1992 the car star engine and run for half milles the engine come to be off and is hard to starting again

  7. worried dad

    My daughters dumb husband bought a 97 eldorado back in November, against my better judgement, i dont know anything about cadilacs except their expensive and hard to work on,, well she precedes to tell me that she would be driving and it would just cut off, she coast and then had a hard time restarting, started out a loose battery cabl, they tightened up and started descent after that, but a wk later he went to Work and now will now start at all,, i yook the battery and had tested and it had a few dead cells,, she bought a new battery and i installed still not even a click with the new battery, , he says he.can hear a clicking on the drivers side but when i tried starting couldnt hear anything, ,, any help at all would be appreciated, , thanks

    • I just parted ways with my 1992 Eldorado .The battery had gone dead when the vanity mirror was left on.
      The theft system turned the fuel pump off as a safety feature when the battery was removed and the computer had to be reset .The ignition switch is the key to reset the computer.The manual will tell what needs to be done.If you work on cars you know the Manuel is your guide .I had the car for 10 years and will miss driving ,but at 68 I can no longer change a tire without killing myself,and dad always said if you are going to drive you have to know how to change a tire.

  8. Tim

    I got the 92 eldorado. The car won’t start. New alt, battery, waterpump, serp belt, and tensioner pulley. I only get a single click when I try to turn it over. The starter is a pain to remove so I haven’t done that but I accidently hotwired it while trying to get a reading off of the solenoid and the starter did turn over. I noticed the ground bolt near the starter was loose and spun in it’s grooves to which it connects to the engine. I am not a mech but did buy a multimeter to try to ascertain the prob. I just need to know what and how to check to ensure I’m getting proper voltage. The car has been sitting for 9 months now. Any help would be greatly appreciated.

  9. Tim

    I should also mention I get no codes off from the obd1 except for something about initiator circuit short to S.I.R. EO24 and 52, but that has been on since I bought the car and didn’t cause an issue before, and it shows up as a H code not a Current code. Again, I’m a novice so any tips would be great.

  10. 1993 Cadillac Fleetwood
    All of a sudden will not crank over. Have replaced, batt., starter switch, have checked all fuses. Have traced what appears to be the issue to the starter relay up under the dash. The following are the results at the starter relay: With the ign. switch in the start position I have 12V power to terminal # 4 YEL wire, I have no 12V power to terminal # 1 YEL wire, I have 12V power to terminal # 2 PPL/WHT wire, I have no power to terminal # 5 BLK/YEL wire going to the CCM. Any help as to what to look for would be appreciated. Jim

  11. Mario

    Hello, I am trying to locate the PDM (PASSKEY decoder module) in the 1990 Cadillac FLEETWOOD FWD. I have looked left to right under dash, nothing in the trunk. HELP!!!! Please.

    I think also known as a TDM (Theft DETERENT module) the part number is 16150920. I just cannot find it.

  12. ’92 Eldorado: battery went dead while ignition in full forward position to play radio while car not running. awoke to find this situation. attempted to start, got no response whatsoever from starter. wrecker arrived – used jumper box, then heavy jumper cables – still absolutely no response from starter. wrecker driver was all over battery & starter, finally gave up saying it was an anti-theft system issue that deliberately was blocking the starter engagement, which inasmuch as there was absolutely no sound or noticeable movement in or around the starter in spite of all the juice directed at it, was exactly what i suspected. 1 person (don’t recall who) suggested i get a new battery for the lock/unlock/shut off alarm push button device, which has been dead since several weeks ago when i bought the car, and stated this should be able to clear intentional blockage to starter engagement.


      1992 HAS THEFT DEVICE.Once battery is removed or disconected the gas pump is turned off.New or good battery added,then I would bypass the gas pump,with a can of starter fluid.Not really a good way to do it but after it starts the pump will work.

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