Cadillac Repair: 1990 CADILAC DEVILLE, ohmeter, lock cylinder

Question
Where is the theft deterent module? i have replaced the key swithch with a new one. the  car will turn over and start for a sec. but acts like the fuel is being cut off so i jumped the fuel relay and the same thing run for a sec. shut down. ignition is being i nterupted buy the security system. is ther anyway to buy pass this anti theft? can i get an older computer with out the vat system programed in it?  

Answer
Hi Robert,

      Lets start at the top. The decoder module is located behind the glovebox to the right of the fuse/relay panel. If you have replaced the ignition lock cylinder with keys then everything should work. The 2 white wires comming from the lock cylinder are the ones that read the key. If you unplug the multiwire connector and use an ohmeter on those 2 wires and turn the key the resistance should remain the same. If it changes readings drastically like 1,500 ohms or more then the wireing is defective or the cylinder wasn't installed correctly. If you measure the key pellet and then go to Radio Shack and buy a 1/4 watt resistor as close to the reading as you can, cut the 2 wires and soldier or tape a wire to each end of the resistor. The car should start.

    There is a starter interrupt relay shown mounted on a bracket above the brake switches. That relay can develope arced contacts and not allow current to flow to the starter.  The 4 wires are yellow, yellow, black/yellow, and pink/black.

    As far as replaceing the computor that wouldn't work because the calibrations for the engine emmissions wouls all be differt as would the wire connectors and locations. Hence a MAJOR rewire job.

     If the relay, resistor or ignition lock cylinder don't get the engine to start I would suggest getting a factor shop manual or go to all data.com or auto zone.com and subscribe to a 1 year subscription to all data and you will then have all the repair info you will need at your computor and be able to diagnos this yourself. Otherwise maybe your mechanic is going to need to help you with this one. Bill