ON A 1993 CADILLAC SEDAN DE VILLE I CANNOT START THE VEHICLE FOR MORE THAN 2 OR 3 SECONDS. IT STARTS AND THEN IT DIES. SEEMS TO ME LIKE THE PROBLEM IS EITHER IN THE LITTLE CHIP INSERTED ON THE KEY OR THERE MIGHT BE AN ANTI-THEFT DEVICE PREVENTING IT FROM STARTING. I WISH I COULD FIND A DIAGRAM TO GET MORE INFO OR IF SOMEONE COULD SHED SOME LIGHT OVER THIS ISSUE, I WILL GREATLY APPRECIATE IT.
I looked at the wiring diagram (through my public library web access). The anti-theft seems to only affect the circuit to energize the starter solenoid. Power comes from fuse #17, goes through the pull-in coil of the Starter Enable Relay, and to the Passkey II Decode Module to complete that circuit. That could be bypassed by joining the yellow wires into and out of the Starter Enable Relay. This relay is between the ignition switch and the neutral safety switch, in the circuit (probably NOT, in physical layout). I think the problem is somewhere else. If it only runs when you hold the ignition key to START, the ignition SWITCH (not ignition LOCK) could be the problem.
You have a starting problem. Your car has a computer and you need a mechanic to read your codes or diagnose the problem. Do yourself a favor and have it towed in. You will save in the long run. Time, if nothing else. They might fix it in an hour.
Maybe the electrical part of the ignition switch is faulty.
You could also try running a hot wire to the ALDL connector (terminal G I believe; lower right) to power up the fuel pump and take the electronics out of the equation. A test method only of course.
I would also recommend checking every fuse on the car. It seems to me that the engine controls, etc. run through 4/5 or maybe even 6 different fuses so maybe there’s a chance that one of those has gone south.
The problem might be with the ignition module.
Ignition modules operate in two modes. These are the start and run modes. When starting the engine, the module allows full battery voltage to the coil(s). This insures that the cold engine starts. Once the engine starts, and the ignition is allowed to move to the run position, the module switches to the run mode. This reduces the voltage to the coil(s) so that secondary ignition components last longer. Much like how ballast resistors/wires worked on older point type ignition systems.
It could be that the run mode of the ignition module has failed. And that’s why the engine starts, but stalls as soon as the ignition is moved to the run position.