2001 eldorado abs problems

[rockfangd]

Hi all. Just started driving my new to me eldorado and am trying to work out the cobwebs.

The ABS, Traction, and Stability lights come on on startup

Code is always c1243. Pump motor stalled

If you clear the code when engine is running and headlights are off code does not return

If you clear the code when the engine is running but loads are on the code immediately returns.

You can hear the motor kick on but it acts like the voltage drops too low and trips the code, also the lights dim.

If you shut the car off and immediately restart it lights are out and no codes.

I also noted something else interesting tonight, If you accelerate hard the headlights dim a bit and come back when you let off.

Here is what I am thinking, I am thinking there is a bad ground or battery connection somewhere, but am just not sure where to look.

I am also thinking that this is why the abs pump code shows up. If the voltage is lower than normal to the abs unit then it will stall the pump.

Battery is new, tests good. 12.6v at battery and cluster

Alternator is new and works good.

No driveability issues other than the lights dimming on hard acceleration.

Engine runs great. trans shifts smooth.

No other codes from any other system

Dash lights, and interior are bright.

I could use some insight on this one as I think there is logical explanation. I was as specific as I could be so I hope it helps. Thanks all

[Cadillac Jim]

The circuit to the ABS motor is: Battery terminal to cable to power bus on Maxifuse block, through 50 Amp BRAKE Maxifuse to EBTCM through two big red wires, through EBTCM relay, through connector to BPMV, through ABS motor, from ground on back of ABS motor to engine ground G107. If the threads on the block were ever stripped out someone may have moved G107 to a chassis ground. The two battery ground cables connect to engine and to chassis ground.

We've addressed the ABS motor, its power, its ground, and the 50 Amp BRAKE Maxifuse on another thread. I'm assuming that you have checked the brake fluid and it's OK, isn't polluted degraded or foamed, and is at a proper level in both master cylinders.

This smacks of a battery cable problem. You know the drill - pry out all three of the connectors in the big red positive battery terminal and clean them. If they don't bolt tightly to the battery, use a copper washer from the auto parts store. The negative cable has two terminals, one to ground the engine and one to a chassis ground, and although it doesn't give the same problems, I would clean that one too. And, check both grounds.

The hot cables go to the alternator, the starter, and the power bus on the Maxifuse block. Make sure that the battery cable is in good condition all the way to each destination, and that it is properly bolted to each terminal. The cable to the Maxifuse block goes through a conduit on the rear of the radiator support. When a dealer tech replaced my battery cable on the 1997 ETC, he threw away the conduit, which protects the cable from road debris. The conduit is split and taped, which means that you can take it off and inspect the cable, and put it back or replace it with new conduit and tape it.

The lights dimming on hard acceleration is a bit of a mystery to me. Perhaps the motor mounts are loose and something is shorting out.

[barczy01]

check the ground on the side of the pump, its get corrosion.

[rockfangd]

I did check the pump ground. Ohms to 0.01. Also checked the single pin plug inline to it.

[KHE]

The code probably sets when the car cycles the pump at startup. You clear the code and it does not return but I bet the code sets if you slam on the brakes so the system tries to activate the ABS.

[Jan Olsson]

I did check the pump ground. Ohms to 0.01. Also checked the single pin plug inline to it.

Did you check if the pump is shorted out?

[rockfangd]

yes I did,. It works fine when the engine is running but not when the engine is not running. Thats why I think the higher voltage from the alternator has something to do with it

[Jan Olsson]

You could try to rule out the possibility of bad terminal connections by raising the front end and back-prove the ABS-unit while an assistant cycles the ABS. If the voltage drops considerably then there has to be a high resistance somewhere in the circuit.

[Jan Olsson]

Resistance between motor stud and battery negative terminal should not exeed 2 ohms and the motor resistance should be between 0.2-10 ohms. Sounds like a bad ground somewhere. The manual suggests the points G107 and G110. G107 is located under the thermostat housing at the automatic transmission. G110 is the one that you've already checked. It could be an idea to check at the underhood fuse block too.

[Cadillac Jim]

G107 is the one directly from the ABS motor and is the one critical to the motor. G110 is needed to give the EBTCM a good ground when the ABS motor is running so that its "ground" doesn't hop up high enough to disrupt its electronics, so if it isn't good then the EBTCM can fritz out when the ABS motor turns on. Thus both grounds must be good for the ABS motor to work.

[rockfangd]

Thanks alot guys.

I believe the grounding problem is to the EBTCM. I have the whole cover off of the fuse area. It all looks good.

So I may be a little confused.

G107 goes to the pump stud but where does it come from?

G110 goes to the EBTCM and comes from the transmission by the thermostat housing?

I definately think there is a grounding problem somewhere but weirdly it is not affecting the engine.

[Cadillac Jim]

The ground from the back of the ABS pump is a big black wire that goes to G107 which, by the FSM, is on the engine block. That wire doesn't go into a wiring harness so you should be able to follow it. The harness ground is on the connector and is a smaller black wire that goes into the harness, then breaks out to go to G110, which is also on the engine block.

When I had my EBTCM fixed by a GM tech, he repaired the big pink wire into the connector; it just pulled out with his fingers. Both G107 and G110 were bad, and both were to chassis grounds. I suspect that the same mechanic that farkled the EBTCM connector stripped both grounds and moved them to chassis grounds. That actually makes better sense to me because the ABS pump power comes from the Maxifuse block and the ground for that is the chassis ground. The battery ground cable has a separate ground for chassis and for the engine; this returns power from the ignition, starter solenoid, and starter - and EBTCM.

[rockfangd]

ok guys. Tonight I took some time and got under the car. I found 2 ground bolts at the front of the block, right by the abs unit.

this is what I found.

lower bolt has one larger wire and what looks like 2 wires taped together going to the same bolt

Upper bolt looks to have one wire going to it.

All looked good. I looked at the connector to the Abs unit and did not find anything obvious.

Now like I said before. If I have the car running with loads on and clear the code the lights go dim and the code comes right back.

If I have the car running and turn the loads off then clear the code I can hear the pump cycle and the code does not return.

Maybe I am thinking about this all wrong. Maybe it is not a ground, maybe it is a power problem somewhere.

I made a new ground cable that goes from the battery to the engine and radiator support near the right headlight.

I ran a ground wire from the radiator support to the abs pump ground and it did not help.

I hope I can figure this out. I dont want to have to replace the abs unit for nothing, Also would like to get it fixed. I cant imagine what the dealer would charge me to figure it out.

[Cadillac Jim]

I would think that if the lights dim and the code comes on, it is trying to run the ABS motor and it is not turning over. It looks like the battery voltage must be over, say, 12.5 Volts to start the ABS motor.

You can't tell whether grounds are OK by looking at them. You must use an Ohmmeter. You added an auxiliary ground to the ABS motor for testing and it didn't help but I'm going to complete the spiel anyway. If the ground is still there, check it with an Ohmmeter and make sure that the resistance is essentially zero. Another thing you can do with a wire hooked to the back of the ABS motor is put a voltmeter on it and see if what it reads when the ABS motor tries to start but fails, and when it starts and runs.

One of the two wires to the engine block goes to the back of the ABS motor without going into the wiring harness, although it may be tied to it. That is probably the large wire. I would take off both ends, clean the parts, and put it back. Be careful with the torque on the aluminum block. Also, clean the other ground too. Check them with an Ohmmeter when you are done. You can check the resistance from the bolt on the ABS motor ground terminal to the engine block as an end-to-end ground check.

Neither ground should have wires taped to it. This means that someone has modified the electrical system and at least cut off the insulation, and possibly damaged the wires. Take off the tape and look at the wires and see. One solution is to clean up and solder the connection so that the solder fills in for any broken wire strands.

[rockfangd]

Ok I will try those.

Nothing looks modified but anything is possible.

You nailed it about not being able to kick in under 12.5 volts. Thats one of the red flags that stumps me. I am also going to check the main cable to the fuse access area at the driver side strut tower. Maybe the whole block is not getting adequate power, maybe ok to run other things but not enough to run the pump.

[Cadillac Jim]

The main battery ground cable to the engine block may be dirty.

[rockfangd]

I just replaced the main battery ground cable to the engine and by the right headlight.

Tonight I found a little time to look at it and here is what I found

Main 12v to the maxi fuse block is good, verified good voltage at all of the fuses. Same situation. If all loads are off with engine running code clears. Pump sounds fine.

Have a few questions now

Is there another main ground to the engine other than the one to the battery?

is there a ground from the engine to the body or subframe?

I ohm between the engine and the radiator support and it seems to be excessive resistance.

Also when I monitor the voltage under heavy acceleration the voltage drops and the lights dim, as soon as I let off the gas everything is normal.

This is starting to stump me but I am having my doubts that the ebtcm or pump is bad, I think it is either a voltage or ground supply problem.

I still think this may be related to the subframe being dropped at one time and not done properly

[Cadillac Jim]

To answer your question, I don't think that there is another engine ground. The dual ground cable on the battery cable *is* the engine ground when things are done that way. You see an engine ground strap when there is only one battery ground cable.

There is a caveat there. The ignition module and possibly things like the ignition harness are grounded to the engine block, and they are grounded through the wiring harness by grounds in the PCM and other modules. If the engine ground is bad, these things can malfunction too.

An Ohmmeter measure the voltage drop produced by a very small current to compute resistance. If there is another current flowing, the reading will be wrong. To be sure, disconnect the negative terminal of the battery and measure the resistance while it is off the battery. If necessary, put a nut on the battery bolt if needed to clamp the two terminals inside the battery ground terminal.

But if you *have* found something, well, 1 Ohm will certainly cause the problem you are seeing.

[rockfangd]

Today I purchased a used abs unit. comes from a 1998 eldorado. jl4 option like mine. The pump is compatible but according to my part cross reference the ebtcm is not.

I am praying it is a good unit and I can swap my ebtcm over to it. This means my eldo will be downed until I can get everything apart and back together. Not sure if any lines will need to be replaced.

Does anyone know if the abs unit and ebtcm can be tested off vehicle?

[Cadillac Jim]

There are several part numbers for the EBTCM. The module in the EBTCM is where ABS, TC and ESC all live. It's where the road force goes to from the RSS, and it commands a reduction in torque to the PCM when needed. I would only exchange them by part number.

[rockfangd]

Thanks. I am hoping I can swap the whole thing but am doubtful. Guess I will find out when I take it all apart

[Cadillac Jim]

There is only one observable difference in the EBTCM that I know of: whether it has one or two relays showing. Since Stabilitrak was standard by 2001 I'm sure that your EBTCM has two relays.

The software for the module, including the inputs from the accelerometers and gyro, the car's network interface including the DTC testing, storing, and reporting, are all in firmware in the EBTCM. Although some part number differences may be attributable to EPROM data that can be changed with a Tech II, if the hard code such as the ESC, ABS and TC algorithms are in ROM, they simply won't interchange between part numbers.

The EBTCM is an easily removable part, if you can lay your hands on it. I would try your old EBTCM because the problem appears to be your ABS pump, which is on the BPMV that you are getting. That will very probably work and if it does you are done. If you switch the EBTCM with the BPMV and it doesn't work...

[rockfangd]

Well guys I have some wonderful news. I installed the abs unit today. It went very well. EBTCM separated easily.

My motor smelled burnt.

I bled the brakes, replaced front pads and rotors, added extra ground to stud on motor.

I can now happily drive the car without it telling me there is something wrong. You can hear a big difference in the sound of the motor.

No lights, codes, dinger. Very nice to be able to take this off my to do list.

I might add that thanks to the underbody condition of this caddy it made things alot easier to work with.

Thanks all for the help

[Cadillac Jim]

We need another smiley, of a bug being vaporized or some such.