Electrical Diagnosis Help - 2001 Cadillac

[turbojimmy]

Okay, this is going to be long but please bear with me.

I have a 2001 Cadillac Deville that is a reconstructed flood total. I restored the car myself and it has been fine for the past 2.5 years. No trouble whatsoever – mechanical, electrical or otherwise. I replaced all of the electronics myself. The only thing original about the electrical system are the wires and connectors themselves. They were all thoroughly cleaned, dried and reassembled. I’d like to think that the problem I’m about to describe is not related to the flood damage, but you never know.

First, I have a remote starter installed along with an ‘interface module’ that works with the body control modules in the car to bypass the anti-theft, honk the horn, flash the lights, etc. It also obviously required hacking into the ignition and starting system. This is where my trouble lies but I’m not sure it’s the remote starter yet.

As I think about it, the trouble probably began a couple of weeks ago but I didn’t realize it at the time. I ran the car through the car wash. They put the car in neutral and shut it off to run it through. When it came out the SECURITY light was flashing and it wouldn’t start. I hit UNLOCK on the aftermarket key fob and then it was okay. It had never done that before but I didn’t think anything of it.

Fast forward to this past Saturday. I came out of the mall after the car had sat for about 20 minutes. When I went to crank it it acted like the battery was weak. The starter solenoid was trying to engage but it wouldn’t crank. Everything else worked fine. The instrument cluster looked funny (random lights) and I could hear popping through the speakers corresponding with each click of the solenoid. I called AAA. While waiting for the tow truck, about 5 minutes later, I tried to start the car and it fired right up.

I drove the car all weekend and it was fine until Sunday afternoon. I was sitting there idling in a parking lot when the dash lit up like a Christmas tree. The car continued to run fine, but I was getting error messages from just about every system. I got the car home and it would not restart. It then began acting really funny. Dash would light up without the key in the ignition. When I turned the key on the gauges wouldn’t work until I put the car in gear. Then when I shut it off it wouldn’t give the key back (couldn’t turn the key the whole way back).

The error codes relate to communications errors between the PCM (engine management), IPC (instrument panel) and the IPM (a body control module). Generally these types of errors are not indications that the modules are bad, but rather voltage or grounding problems with one or some of them. Finding it, however, will be like finding a needle in a haystack.

My plan of attack is to first take out the aftermarket starter and interface module. I also had the intake manifold off of it last week to repair a leaky plenum. In what might not be a coincidence, the starter wires (the lug off the batter and the solenoid control wiring) run under the intake. I need to check that out as well.

The car has deteriorated to the point where when I hook up the battery I get nothing but a pathetic clicking from the instrument cluster. Everything else (lights, radio, keyless entry, etc.) works except the climate control, which is part of the IPM (for which I have a serial data error code). I’ve replaced the battery with a known good one and that didn’t help.

If anybody has any advice (other than torching the car) I’d appreciate it. Also, how do I check the resistance across a wire with a DVOM? I have a DVOM but I don’t know how to use it other than to check for voltage.

TIA,
Jim

 

[Nick Micale]

Jimmy, I have a local friend that was a tech at a local dealer until he opened his own shop a few years ago. He does lots of stuff with late model Cads including turbos, sand rails, etc.

Contact me direct and can hook you up with him if you like.

 

[garyk1970]

being a ex-caddy tech, there were alot of problems with the ground cable from battery to floor pan(stud where ground attached)not to mention all the floors eaten through by acid . get a meter out and verify voltage on battery verses body....
also alot of these series batteries( if its a delco) has problem with the terminal breaking inside the battery. supposed to be a copper washer, everyone throws them away, then bolt goes in too deep, and busts battery inside.... HTH

 

[turbojimmy]

Thanks both for your replies. I'm going to check the grounds before I hack out the remote starter. In theory, the remote starter shouldn't have anything to do with not cranking. I'm getting the crank command from the PCM (which should eliminate the remote starter as a problem) but there's just not enough juice to turn the starter. Now there's not enough juice to do much of anything.

My battery hasn't eaten through the floor yet. It's actually in pretty good shape. I guess if you don't put the vents on you can have all sorts of trouble. The battery was new with the restoration. I don't have any spacers on the lugs, but neither did my mom's 2002 Deville. I stole her battery for testing purposes but that wasn't the problem.

Nick - I may take you up on your offer as I dig deeper into this.

Thanks again,
Jim

 

[garyk1970]

your alarm/remote starter doesnt have ign kill does it? still sounds like a voltage drop/surge with the description of the IP.

the lug to body will look OK, verify voltage with meter.

 

[turbojimmy]

your alarm/remote starter doesnt have ign kill does it? still sounds like a voltage drop/surge with the description of the IP.

the lug to body will look OK, verify voltage with meter.

It does have a ignition kill by way of interrupting the crank circuit, but I've eliminated that as the cause. It's actually a pain because the voltage is dropping so low that the remote starter resets itself and kills the crank function unless I hit unlock on the key fob. I can tell when that happens by the behavior of the IP. It's definitely a voltage drop or surge but where or why is the question.

The DIC was reporting 12.3 volts with the key on, engine off and 14.3 with the engine running. I don't know where it collects that data from, I assume the PCM. Now the DIC isn't reporting anything since it's lost communication with the PCM and BCM (all the values are "---" now). The DIC could be reporting good voltage even if I had a problem somewhere else depending on where it collects the information from. Also, if memory serves the IP does not have anything to do with the crank function - it's just collecting and reporting data (i.e., a bad IP wouldn't prevent it from starting)?

To check the voltage I could tap into the trouble circuit (i.e., the one that feeds the IP) and see what it says right?

Thanks for the advice.

Jim

 

[garyk1970]

yes the oem anti theft "goes through" the IP. the IP ,BCM(S) and ECM all "talk" through the data link wire (purple).
yes keep doing voltage drops and see where the voltage is the least. like posted before , start at battery and work forward ( pay close attention to that ground lug).

 

[turbojimmy]

yes the oem anti theft "goes through" the IP. the IP ,BCM(S) and ECM all "talk" through the data link wire (purple).
yes keep doing voltage drops and see where the voltage is the least. like posted before , start at battery and work forward ( pay close attention to that ground lug).

Thanks for the info. This hasn't degraded into an anti-theft issue (yet). I had an issue with the anti-theft system when I first got it because the IP is out of another car. Shut it right down.

This is something different though. The car didn't even behave this badly when it was still soaking wet!

Jim

 

[garyk1970]

KEEP US POSTED.... check all the "stupid stuff" first

 

[TURBOTWIN2]

My two cents worth. First, make sure the Battery is fully charged and TESTS good. A sulfated (high internal resistance) battery can make weird things happen. Modern car computers and modules don't really like 11.5 volts or less. Second, check (and clean) your main power and ground connections. Learn how to do a voltage drop test, it's not hard or complicated. Basically less than .1 volts drop (used) across a connection is good. Any more and you've got a high resistance connection, bad for electrical flow. Seems you'll find more problems on the ground side of things. Hope this helps and good luck.

 

[turbojimmy]

Okay here's the deal.

I got home from work and cleaned up that ground under the seat. No dice. While I was goofing around the car wouldn't give me my ignition key back. Couldn't turn the key the whole way to off. Gauges aren't working, the door chime is very slow. The DIC isn't telling me anything anymore (yesterday it was still telling me oil and transmission life).

I'm standing there cursing under my breath and I think I hear the fuel pump running. WTF? I popped the hood to listen for fuel moving through the rail. I lean in for a closer listen and it stops. I stand up again and it starts again. Lean in and it stops. Fascinating.

When I leaned in I was pushing on the underhood fuse box. I grabbed it with both hands and wiggled it. Relays clicked, chimes chimed and the car went to 'exit' mode and released the key. Eureka.

The underhood fuse panel consists of two halves. The top half is loose from the bottom half. I had replaced the idler pulley on the car about 6 months ago and had to pry that out of the way. As I was doing it I thought to myself "I should be careful with this....but what's the worst that could happen?".

So it's related to that fuse box. Not sure how to fix it yet but at least I've pin-pointed the problem.

Thanks all for your help!

Jim

 

[garyk1970]

cool.is there a main pos battery cable that bolts into the box that can be tightened?

 

[turbojimmy]

cool.is there a main pos battery cable that bolts into the box that can be tightened?

There is, but I cleaned and tightened it yesterday. There's some looseness/badness going on with the wiring coming into it. Evidently I had pinched at least two wires when I put it back together 6 months ago. A tan/white wire (which I think goes to the PCM) and an orange wire (constant hot for something) are pinched and probably broken. When I wiggle the box all sorts of good stuff happens. Definitely the cause of my problem. The question now is which of the 500 wires coming out of it needs repaired?

I'm relieved to have narrowed it down anyway. And I didn't have to hack out the remote starter.

Jim

 

[garyk1970]

Ive got a small volt meter with baby pins soldered to it so i can pierce the insulation of a wire with minimal intrusion. turn car on , do voltage drops every inch of each wire that looks pinched or damaged,see where the drop is. yellow,orange wires to look for. but can be any , colors dont mean much

also, try a localize some "wire wiggles" while car is on to weed out the culprit.

 

[turbojimmy]

Ive got a small volt meter with baby pins soldered to it so i can pierce the insulation of a wire with minimal intrusion. turn car on , do voltage drops every inch of each wire that looks pinched or damaged,see where the drop is. yellow,orange wires to look for. but can be any , colors dont mean much

also, try a localize some "wire wiggles" while car is on to weed out the culprit.

Thanks - I'll try that. With the positive lugs installed I don't get much slack on the harness, but I'll sort it out. That orange wire is suspect. The copper is exposed on it. It's not a big wire, but none of them are. If it feeds the IP or any of the modules that could do it.

Jim

 

[turbojimmy]

Welllll.....I'm not out of the woods yet. This is by far the most screwed up thing I've ever seen.

I removed the fuse box, cleaned up all the terminals, visually inspected the wires and put it back in. The two questionable wires (the pinched ones) were for the RH parking light and headlamp relay. I don't have any trouble with either one of those so I left them alone. The car still does the same thing.

So, I left the key on and rocked the fuse box and it did the usual - chimes chimed, doors locked by themselves, etc. I grabbed the harnesses that come into the fuse box to try to duplicate it. Didn't seem to do it. Then I noticed that A/C accumulator is attached to the same bracket as the fuse box. I wiggled the condenser and duplicated the problem. Eventually I narrowed it down to one metal A/C line. If I lift up slightly on that a/c line the car goes back to 'normal' (though it still won't crank). I pull up and down on it I can get the car to flip out (fuel pump running, relays clicking door chime, doors lock/unlock, etc.).

The screwed up thing is that I don't see where that line is touching anything. It must either be completing a circuit or interrupting one by way of a short. There is a lot going on in that part of the engine compartment - lots of wiring harnesses run through there and into the fuse box. That metal line might be touching something else that is shorted out and thus completing a circuit - I don't know. It's driving me nuts but I'm out of time. I'm going to be out of town for the next couple of weeks.

To be continued.....

Jim

 

[garyk1970]

take the ground side of some jumper cables and connect the body to the engine and see if the ac lines are grounding the engine somehow???

 

[turbojimmy]

take the ground side of some jumper cables and connect the body to the engine and see if the ac lines are grounding the engine somehow???

I put a DVOM on it to check for continuity between the body and the a/c line and didn't get any. I think I've talked myself out of the a/c line theory. If I move the fuse box ever so slightly it will do it. Since the a/c line is attached to the same bracket as the fuse box moving the line accomplishes the same thing. I need to take the bracket off and see what's going on under there.

The car started, ran and drove fine briefly. All the codes cleared and everything worked as it should. I stopped it and started it a few times. I came back 30 minutes later and it's gone wacky again.

I'll figure it out - just not until after the 26th.

Jim

 

[garyk1970]

i wish i could get my hands on it:biggrin: i love a challenge like this:biggrin: hard to help over the net.

the more strange/difficult problem, the more i enjoy the challenge of the diagnoses and repair.

 

[turbojimmy]

i wish i could get my hands on it:biggrin: i love a challenge like this:biggrin: hard to help over the net.

the more strange/difficult problem, the more i enjoy the challenge of the diagnoses and repair.

Believe me I wish I could give it to you. It is going to be in the back of my mind the entire time I'm on vacation.

It really is an interesting problem. I've never seen anything like it. I love a challenge too, but not when my other car (the GN) is also out of service!

I'll figure it out, it's just a matter of time.

Jim