95 Deville ghost electrical problems. Suggestions?

[oregonk5]

If you've seen any of my past threads, I'm still battling random weirdness on my 95 Deville.

It started with occasional failure of the dash HVAC fan to blow. Next was Traction Disabled warning light staying on. Later the cruise control started working intermittently and now is completely off. Now the Trunk Open warning light is on all the time.

Throughout the process there has been a multitude of codes, most of these codes have to do with PCM communication failure. I've cleaned grounds, cleaned fuses, tried a different ECM, checked the EBTCM connections. So far nothing has changed.

Anyone have any thoughts on this?

[Cadillac Jim]

It sounds like your battery may be going down. Or, perhaps you can clean your battery cables and clear things up.

[oregonk5]

Hmm, good thought. I actually did clean the connections awhile back when I went on my ground cleaning bender. It hasn't given been dead or anything but maybe it would be worth a try to swap in another.

[Cadillac Jim]

I use a trickle charger on my car when I don't drive it for more than a few days. My wife's car sometime isn't driven for a week or more; I leave it on the charger overnight when I see that the battery is low.

[oregonk5]

So this morning I swapped out my battery and cleaned the connections. Here's the result:

1. Interior lighting and keyless entry still inop

2. Started driving, no warning lights on. "Cruise Engaged" comes on DIS when button is pushed but cruise still doesn't work.

3. At mile 5.9 "Trunk Open" and "Traction Disabled" both come back on.

When I got to work I grabbed the codes out of the CCC:

P052

I032

I052

NO ACP

NO SIR

T072

T077

[Cadillac Jim]

P052 (E052) PCM Memory Reset
I032 Loss of ABS/TCS Data
I052 Keep Alive Memory Error
T072 Serial Data Link Fault
T077 PCM - Serial Data Link Error

The X052 errors happen when you disconnect the battery and go away in a couple of weeks so you can ignore them.

The I032, T072 and T077 all tell us that the EBTCM is offline. I don't have a 1995 FSM but my 1997 FSM says that the fuses for the EBTCM are in the engine compartment fuse/relay center. They are the 50 Amp Maxifuse labeled BRAKES, the 20 Amp STOP fuse (for the stop lights) and the 10 Amp ABS fuse. Check those, and also look at the EBTCM connector. The EBTCM is the module bolted to the brake manifold, where all the master cylinder lines go and also all the brake lines form the four wheels go, and the ABS pump motor is on the brake manifold. The FSM says to take off the air cleaner and reach down there to access it; you may have better luck from under the car. There are two grounds, separate and both very important, on the EBTCM. One is from the back of the pump motor and is a single wire that goes straight to a chassis ground (or to the engine block). The other is through the connector into the wiring harness but breaks out just a few inches later and goes to a chassis ground. Both of them must be good.

There are two big red wires, a big pink wire, and a smaller black wire on the connector. Resistance to ground from the black wire must be well under 1 Ohm. The bit red wires must both be at battery voltage all the time, even when the key is off. The big pink wire will read battery voltage when the key is in RUN or OFF, but not in LOCK or OFF, START or ACC.

[oregonk5]

Jim, you are a wealth of information! I will do my homework and report back in a couple days. Thanks!

[Cadillac Jim]

Yeah, I had a 1997 ETC for fifteen years and learned my way around the 1997 FSM helping out others on Caddyinfo, and occasionally working with my own car. I had an elusive problem with my EBTCM that turned out to be a mechanic-installed problem with the connector; the big pink wire had been pulled out of the connector and just shoved back into it. This was NOT a Goodwrench tech. A goodwrench tech fixed it in an hour after I chased it for months trying to get other techs to fix it. I know all about the EBTCM because of that.

[rockfangd]

you know I would give a good inspection to the electrical center under the hood and look for corrosion or rust. Even in the fuse spots, bus bars, ground connections, etc...

[oregonk5]

^{So this afternoon I laced into the car. First I performed Cadillac Jim's tests on the EBTCM.}

^{I actually bared the wiring harness back all the way and inspected the wires...nothing broke or chafed.}

^{Next, I checked the ground resistance on the two ground wires...well within spec. I cleaned the connections all though they were good since I had done this in previous TS sessions.}

^{Checked the EBTCM plug over carefully, no wires pulled out of the connector. The ground continuity is good and power is present when and where it's supposed to be. (Sorry Jim, no pink wire on the '95 model I guess.}

^{Next I pulled the ECM out, check all the connections. I pulled the bulkhead connector out and pulled the whole harness through the firewall. Tomorrow I will pin out the ECM connectors.}

^{I really think that the Traction Control lights are just a symptom and not the cause. I'm leaning to a defective ECM or PROM (although it's odd that the used ECM I swapped in would have the same problems?). Or perhaps faulty ground or connection and the ECM. All the erratic functioning pretty much has to point at ECM or power supply, right? From my reading about the system in AllData the ECM/PCM and Serial Data Bus are the common denominator in all the troubled systems.}

[oregonk5]

Hmmm, just doing some reading and maybe my previous statement was erroneous. It looks like the ECM/PCM pretty much controls ignition, fuel, cruise, HVAC, etc. but doesn't do anything with ABS or Traction Control; that job falls on the EBTCM.

Perhaps dealing with two separate system malfunctions or a common problem like bad ground, ripple voltage, etc?

Just thinking out loud here....

[Cadillac Jim]

I think you probably have a bad EBTCM. Someone with a Tech II and is knowledgeable about talking to the EBTCM with it can tell for sure.

[oregonk5]

I have a Tech II but at this point I'm not ready to condemn it although I'm getting close! I don't use the Tech II very often so navigating it is a chore and this car is OBD 1.5 so that adds a little mystery to everything!

[Cadillac Jim]

Use the Tech II to talk to the EBTCM. If it is dead, it won't answer any questions.

[oregonk5]

So today I was in full on troubleshooting mode! I cleaned every ground and connection that I could find. I completely bared the EBTCM wiring harness and inspected every inch of it. Even pulled the whole ECM wiring harness and bulk head connector out to inspect it.

After I got it all back together and made sure any remaining codes were clear I fired it up and ran it on jackstands.

Didn't take long for the Traction Disabled message to come on. It also had some crazy wheel speed readings.

The Tech II worked fine on the Powertrain and Body data displays but as soon as I went to the ABS diagnostics it kept losing communication with the Tech II, even though it was plugged in securely.

I think it leaves little doubt that the EBTCM has gone south. As far as why the cruise isn't functioning maybe replacing the EBTCM will fix everything? One can hope!

[Texas Jim]

If you have any suspension codes, the Cruise will NOT work...

[oregonk5]

Alas my troubles continue.

Put in the used EBTCM. All seemed to be going well for the first 4 miles of the test drive. Cruise control still didn't work but no "Traction Disabled" messages. Strangely the CCC controls didn't respond very quickly.

At mile 4.5 I pulled over and "Traction Disabled" message came on. Also the PRNDL was flashing. While sitting there I pulled a code C0072 IPS Serial Data Malfunction. Eventually the message came on and I drove home without it ever returning.

Not sure where to go next. Thoughts?

[oregonk5]

Well I might be on to something. While sitting with the key on and Tech II and in the data display mode I kept losing connection with the system.

I pulled the DLC down and checked all the wiring...next wiggled all the under dash wiring I could touch. Nothing seemed to make a difference but it kept intermittently losing connection.

Finally I pulled the dash cover off and as soon as I wiggled the IPC/CCC connector it lose connection. I tried to narrow it down to a particular wire but couldn't touch the connection without losing connection. The connector and pins look ok so when I get a chance I will remove the IPC. Hoping I will find a cracked control board or bad solder joint.

[Cadillac Jim]

Often this type of problem is a wire broken off inside a connector at the point where the terminal is crimped onto the wire. Try gently pulling on each wire in the DLC connector at both the DLC and IPM ends. Since any of ground, data, or power wires could be causing this, check all of them.

[oregonk5]

Took out the instrument panel this evening. Inspected both the plugs very thoroughly, no broken pins or bad connections.

Took apart the IPC and checked the ribbon cable, solder connections under a magnifying glass, etc. Nothing obvious.

Plugged it back in and all seemed well. No matter how much I wiggled connections the light wouldn't trigger or lose connection.

Ran a hair dryer on the IPC board to see if it loosened up any connection. Nope. Blew compressed air on it....no failure.

Cleared all the codes and prepared to back it out...as soon as I put my foot on the brake and dropped it in gear the Traction Disabled light came on. Wiggled all the connections but nothing would make it turn off.

What say you? Time to try an IPC?

[oregonk5]

Well some light at the end of the tunnel! Found that the problem with the cruise control was a broken vacuum line!

Also discovered the DLC connector has a shunt in it that is part of the UART system. My connector has been uncovered for a long time, although the recent failures have occurred with the scan tool plugged in. As a long shot, I put the DLC cover back on and drove it about 4 miles. So far no light but I'm not holding out much faith!

[Cadillac Jim]

I think we need a fresh set of codes. Try resetting them and see what comes back.

You might also check the brake switch and the shifter lockout switch.

[oregonk5]

Only current codes I pull with the Tech II are in the Chassis-ABS section.

C0072 IPC Serial Data Line Malfunction

C0077 PCM Serial Data Line Malfunction

[Cadillac Jim]

C0072 Brake Temperature Too High
C0077 Low Tire Pressure

If your codes are correct, and I'm assuming that the ones I have from the web are wrong and yours are right, you have a problem wiht the network line between the PCM and the IPC. This has got to be related to the bad connection on the DLC line, which goes to the DIM, which is the module that the IPC talks to (and all the other modules). If the codes are CURRENT, you haven't found the bad connection under the dash yet.

[oregonk5]

The codes I posted are the description listed on the Tech II.

Today I cleared all the codes, put the DLC cover on and drove it all day...over 60 miles. The light never came on.

I'm not declaring a victory because the problem has been intermittent in the past, sometimes it would take days to manifest itself although recently it has happened almost immediately.

Time will tell.