Car will not stop

Odd, I put model in. It is a Deville.

FYI, We dropped the steering column and completely disconnected the ignition and it kept running. If the ignition was shorted out, taking it out of the loop should have removed the short and let the ECM take over, right?

VIN: 1G6KE54Y2XU7760331

Solve it and I will happily pay for the service information!

Estimate to replace ECM wax $705.00 from Cadillac dealership. Online parts have the ECM for under $100.00 but the programming. There is one site that says if you send them VIN they can program it but I have concerns.

Headlights. And that seems a recent thing although my dad described it as a "feature".

Limited tools but access to a mechanic friend. I can start pulling relays to see if it shuts off though.

One thing to keep in mind - I took this in to an older gentleman who has his own shop and has been servicing Cadillac's specifically for thirty years (funeral homes, special markets). He's pretty well recommended. He had it for three weeks and could not find the issue, and he did not charge me because he said he did not fix anything. He was the second person I had look at it. The first was the one who helped me pull the ignition and check the relays and fuses, I only mention this to provide some comfort that routine options have been checked.

Other probably irrelevant pieces of information. The gas shocks have all been unplugged for awhile now, just bottoming out on springs. The radiator, power steering, and serpentine main belt have all been replaced recently. Nothing unique stands out as happening the day the issue started.

Windows, seats, dash, radio all work although dash is very dim.

One other interesting thing that seems to get written off by folks I talk too. Starting a few days, maybe a week, before the will not stop issue arose, we started getting two error messages at the dash plus the car was overheating when it sat (229 degrees) but would quickly cool down (180ish) if I started driving it.

The first light I was getting were (not exact wording) Service AC. The shop guy said ignore it until summer but I note that it may have indicated a thermostat issue that might be related to the overheating. Do not know, did not address per advise.

The second light feels like it might be related but shop folks ignored it do maybe not. We started getting an "Anti-theft System Error - Car May Not Start Once Turned Off".

The "will not stop" problem started after about two weeks of these messages.

It's a mystery that's for sure. So, how long before the car would stop? Not until it ran out of gas. Its a smooth, consistent idle and it doesn't stop.

There is some kind of constant drain on the battery when it does stop, though, as the battery will die if I don't unscrew the positive post whenever it is going to sit for any length of time (1 hour or more). As I mentioned earlier, the headlights stay on, but they were doing that before this new challenge. And they would eventually go off as the battery did not die.

I am 90% sure everything works when it is running - seats, windows, lights, radio I've seen work after key removed.

I did not see any grounding issues on panel but I'm going to leave that one open to get a second set of eyes to confirm.

Water in which fuse box - trunk, drivers feet, under hood? They all looked pretty clean to me, and no blackened or discolored areas when I pulled fuses.

Here's something I noticed, its been there awhile though so its not a direct cause. There is a very small red wire that connects the passenger side of the ECS and CC fuses under the hood. Its wedged into one side slots. I"m clueless on that. ECS has a pretty big role though, manual says:

"ECS Transaxle Shift Solenoids, Mass Airflow, Canister Purge, PCM, Linear Exhaust Gas Recirculat, Front Ignition-1 Relay

CRUISE Stepper Motor Cruise Control, Power Steering Pressure Switch, Low Refrigerant Pressure Cutoff Switch, Park Rela"

Like I said, the jumper has been there awhile, but why.

Also mentioned before, the gas shocks have been disconnected. Some of the wire harnesses are hanging inside the engine cop

Something is shorted to constant power. I don't know the exact loop of power for a running engine, but I do know that when we completely disconnected the ignition from the column, it kept running, so the ignition isn't the short. When I pull the ECM (IGN) fuse- bottom block of fuses, second row, second column - engine shuts off. That has to be the circuit being shorted, right? At some point after the fuse box so that pulling the fuse still shuts it down. Or a circuitry short in the ECM. Do you have the wiring diagrams?

Also, there is activity and a kind of slide-click noise followed by a hummy kind of noise but not "humming" per se. Seems something is coming alive when I put the PCM (IGN) fuse back in

Yes there is current on both sides of the CC fuse.

I started calling around to find out about the jumper and who put it there. As it turns out, the jumper CC to ECS was installed on purpose to do exactly what you described. Apparently the fuse box has a short or bad solder in it and a prior mechanic jumped the circuits to keep power in the box.

That worked for 2 years until now. Now the question is, what else failed breaking the earlier "fix"? Something that accepted the ignition key switch to off as killing power no longer works.

You've laid out the power path in the previous message, what might it be? Or is it likely the ECM at this point?

If I replace the ecm, should I replace the fuse box too so that jumper can be eliminated or keep the cheap fix? Or do I do just the fuse box first in case something else with it went wrong? And is there any way to diagnose the box to confirm that it is the source? Are there other candidates the jumper was meant to deal with like a switch I should check?

More info. No power in harness to AC so AC compressor not kicking in. Power at switch, fuse and high control. Off market harness with splicing and electrical tape. Also, you mentioned diode elsewhere in system. Found the below image of a crossover clip snapped on compressor harness about 18" from compressor May be unrelated but thought odd. Conoresdor tepksved in 4Q 2016. Unclear if worked at time dad said "its winter why would I check AC."

Yep. Trying to find one now. But also trying to deal with compressor issue. And wondering about that clip. What purpose does that clip serve, can you tell?