2003 Deville Strange Starting Issues

[93SixtySpecial]

Hello all,

I'm posting this for my father-in-law who is having some issues with his Cadillac. Hope someone has some ideas!

2003 Cadillac Deville, base model, 118,000 miles. Prior problems: NONE

Background:

No problems prior with car. Worked perfect.

Had doors open for a few hours while cleaning seats and dash.

Key was NOT in the ignition.

Suspect battery went dead as car would not start after the cleaning. No liquids were used during cleaning.


Problem:

Battery went dead from doors being open too long (we think).

Tried to jump it under the hood and it would not start. Took battery out and charged it off the car put it back in and car starts.

Car will run for days with no problems then it wont start again. No click, no nothing.

Sometimes it will do this problem 3 times a day, sometimes it will go 3 or 4 days and not act up at all.

Charging system shows it is working good when it does start.

Car will NOT die from this problem. As long as it is running it will run forever. Problem is only in starting.

When the problem is present, the dash lights up like normal but it will not show fuel level or coolant temp level but the gages light up and look like they are working. Also, radio and interior lights will not work. Car will not start, wont even click.

When car finally starts it starts flashing all kinds of things on the dash info panel like no data being received from any sensors like wheels, body, etc. Then in a few seconds all is normal.

Whenever the car wont start I check the voltage at the battery and it shows 12.6 volts (at the battery). If you turn on the headlights and try to crank the car the headlights do not dim at all.

HOWEVER, if I hook up jumper cables at the BATTERY the car starts right up, runs again for days then does the same thing. The car will NOT start if you hook up the jumper cables under the hood.

What I have tried:

Unplugging battery rundown fuse, left out door module fuses, left out dig lighter and dome fuse, etc.

Replaced the $200 battery. Said goodbye to my $200 as it does the same thing.

Problem is not present all the time. Sometimes it will go for days and work perfect. Then for no reason it wont start again.

Strange thing, there are no codes because when you try to check them it says "no data" from anything.

However, I did find out if I take off the negative battery cable and put back on the car starts every time. It seems like the system is not being "energized" and by taking the cable off and putting back on it works every time. However, it is soon to be -30 here and don't want to keep taking the back seat out to take the battery cable off and put back on every time we use the car.

I thought it may be a bad PCM or PCM connection. He also mentioned that sometimes at a stop light the door locks will randomly cycle. I had him check the codes after an episode and there were a ton of U-codes in all the modules. This is another reason that I was suspecting a bad PCM because of all of them being effected. There were no current codes though, only history.

[KHE]

It sure sounds like something is going on with the battery cable or connection. $200 for a battery? Ouch.

I would connect an ammeter in series with the negative lead of the battery and wait for the computers to go into sleep mode and see what the current draw is. It should be less than 30 mA - if not, there is a parasitic drain somewhere and you'll need to pull fuses until you find the one that causes the ammeter to fall beloe 30 mA.

[barczy01]

There is a ground cable on the motor that tears and causes issues with the electrical system. It's on the rf frame rail and attaches to the alternator. Check the end on the alternator side for fraying.