"Service Brake System" / EBCM

Pittfan

Original poster
Member
Jul 22, 2012
10
Hey all,

First off. This is my first post on this site. Glad to have found it. I was on the other site, but it seems to be going downhill quickly! Anyways, I will refrain from those comments (for now, and for a different discussion area).

I drive a 2004 Envoy (126,000 miles, I6, 4x4).

About 3 months ago, I was driving to lunch one day, and the ABS and Brake Light came on, along with the DIC message "service brake system". There were also about 30 chimes that go off when the lights came on, and the chimes last about 8 seconds.

I had the ABS code scanned. The code (which I don't remember the actually code number) came out to be "lost communication with the EBCM". So, I naturally checked the ground wire (under the Envoy, in front of the driver's door). I took it off, cleaned it up with a wire brush, and put it back on. Still have the same issue when reading it with the code scanner.

I put the Envoy up on a lift, and started poking and prodding just to see what I could see. I pulled 2 of the wire harnesses out of the EBCM, and they both seemed to be looking good. Nothing out of the ordinary. No dirt, or corrosion. Then there it was!

I had to remove some of the hard black plastic covering the wires, and found a small little nick in one of the wires (for the EBCM power). As I peeled back the plastic coating around the wire, it turned out that the wire was cut almost completely through. It was also packed with the green corrosion. There was actually only 2 tiny strands of the wire holding it together. I thought that this is why the problem was so intermittent at the onset of the problem.

I cleaned it up as much as I could, and I didn't have much wire to splice back together. I did what I could, then I got out the solder gun, and did what I could. I plugged it back in, and the problem did not go away.

I did check the fuses for the EBCM.

I then purchased a new power connector for the EBCM, which did not resolve the issue.

Unlike the early onset of the issue, the ABS and E-Brake lights stay on all of the time now. And, about once a week, the door chime will ring like it always has. It's nice that the door chime doesn't go off as much anymore, but IF I ever decide to sell this vehicle, it sure would be nice if those lights would not be on!

I am wondering if the EBCM unit is fried. And, if that is the case, is there any way of testing the EBCM without just putting a brand new one in?

I have heard that a new EBCM can cost up to $900-1,000. That's quite a bit of money to throw at it when it might not be bad at all.

Also, I have heard that if you do replace the EBCM, you need to take the vehicle to the dealer to have it programmed. Not too sure why you would have to do that for the ABS.

Thanks!
Jason
 

Chickenhawk

Member
Dec 6, 2011
782
You have two possible issues that I would explore before you spend the money on a new EBCM. When you clean that ground, you should put on a star lock washer under a new bolt just to be certain it is making positive contact with the frame.

The other issue (I read your post on the "other" site) is that your battery is bad or your battery cables are loose. Your voltage should not jump around like that. Tighten your cables and get your battery load-tested. (It is very easy to have the cables loose and not realize it because they can appear to be tight when it is just tight against the battery case and not the battery itself. This can cause all kinds of intermittent problems, such as poor starting, poor running and your clock radio defaulting to 1:00 on a regular basis.)

Let us know what your load-test readings are. (They will be able to show you the reading in CCA, and if it is much under 550 CCA, then it is time for a new battery.)
 

Mooseman

Moderator
Dec 4, 2011
25,472
Ottawa, ON
Download the manuals (check my signature) and there is a whole section on the ABS with diagrams and wiring schematics as well as troubleshooting guides. Did you check the other connector? One of the wires in that connector is for Ignition power. Check with a multimeter if voltage is getting to the ABS module plugs. If not, check upstream from there for broken wiring all the way to the fuses.

One thing you may want to consider if the ABS unit is proven to be defective is to get a used one from a boneyard, especially if you are considering selling it. Either way, it does have to be calibrated by the dealer for tire size. One thing to note is that the EBCM (the brains) and the BPMV (the muscle) are two separate parts and that you don't need to replace both, just the plastic one that the connectors go onto held in by Torx screws. At least you wouldn't have to bleed the system by replacing both, which would also require the dealer to perform to cycle the valves in the BPMV to bleed all the air out.
 

jimmyjam

Member
Nov 18, 2011
1,634
i'd recommend checking power and grounds through a 35w bulb, not just a continuity check. i've seen continuity check pass and subsequent load checks fail
 

Pittfan

Original poster
Member
Jul 22, 2012
10
Sorry. I have been called to work (8am-10pm, 7 days a week) until August 19! So unfortunately it has been very difficult to do anything on my Envoy. I will post more as soon as I can get a little time off to work on it more.

In the meantime, I did pick up a star washer to put on the ground. I also had the battery (and alternator) tested (twice). They both passed at both parts stores. Autozone's tool does not display the readouts from the battery, but Advance Auto does. The battery came out to 556 CCA.

I am going to put the new washer on the Envoy as soon as I can.

Again, thanks for the patience. Not enjoying this work schedule very much....... Ugh!
 

Pittfan

Original poster
Member
Jul 22, 2012
10
It has taken me some time to get back to fixing this problem, but here I am.

I will be attaching the star lock washer this evening. I had a load test performed at Advance Auto Parts, and the battery is in great shape. The CCA were 560. I have not experienced any problems now that can be related to the battery itself (that I am aware of). I was trying to perform a price check on the EBCM. I did see them listed on websites this past spring for around $700. But now they seem to be gone. Does anyone know of another name for the EBCM? I do realize that there are two parts to the system, the BPMV and the EBCM, but I can't seem to pull up the EBCM on any of the searches.

I'll let you know if they star lock washer does any good, and I will be checking the entire run of the wires for any cracks.

Thanks!
Pittfan
 

Mooseman

Moderator
Dec 4, 2011
25,472
Ottawa, ON

Pittfan

Original poster
Member
Jul 22, 2012
10
Yes, I believe that is the part that I am looking for. I thought that they called the part an electronic brake control module (the EBCM), so I have been looking for that online. And, there have been zero results. But when searching for the Brake Control Module, I have had some success. Not that the name really matters. I am just trying to find the right part. I was under the Envoy last night (replacing the fuel pump), and it looks like to me that the ACDELCO 10356388 is that part that I need. I just wanted to see if any of you had to replace this in the past. Or, if there is a good way to test this unit. I did put the new star lock washer on the ground wire to the ebcm, and I followed the wires leading to the control module last night, doesn't appear to be any damage whatsoever.

Thanks.
 

Chickenhawk

Member
Dec 6, 2011
782
Keep us appraised.

The TSBs for this issue have evolved slightly in the past two years. GM used to advise mechanics to unbolt that ground and clean the bolt, ring and frame with a whiz wheel. Now, they advise mechanics to install a new bolt in the frame, so it appears this problem is not uncommon and a very good ground is needed, especially in this spot exposed to all the elements.

So make sure you clean the wire contact and frame to bare metal, tighten the bolt firmly and then respray the area with rubber undercoating.

Hopefully, that solves your problem.
 

Pittfan

Original poster
Member
Jul 22, 2012
10
So, I know that it has been a while since I last updated this thread.

The star washer did not make a difference. I finally took the Envoy in to the dealer, and they diagnosed it with needing a new EBCM. I am prepared to go ahead and replace it myself. Does anyone have a "how to" on replacing it? Seems like a fairly straight forward project. Disconnect the battery and go to town. One question I do have is, can I drive the vehicle after replacing it? Some have said that I can't even drive it to the dealer to have it reprogrammed.

Thanks!
Jason
 

jimmyjam

Member
Nov 18, 2011
1,634
EBCM REPLACEMENT
If the electronic brake control module (EBCM) is replaced, the following procedures must be performed:

EBCM Reprogramming-Refer to Service Programming System (SPS).
Revise the tire calibration using the Scan Tool Tire Size calibration function.
 

mrphoenix80

Member
Jan 1, 2013
251
If you are replacing the EBCM only you can drive it to the dealer to have it programed. If you open the brake lines then the unit needs bleed and you will have no brakes. However you DO NOT HAVE TO remove the brake lines to replace the EBCM it is held on to the BPMV unit with 4 torx bit screws.
 

Pittfan

Original poster
Member
Jul 22, 2012
10
Thanks.

I just ordered the EBCM from RockAuto. I'll post an update after the repair is complete. I plan on doing the installation myself, and then taking it to the dealer to have it reprogrammed soon thereafter.

Jason
 

Pittfan

Original poster
Member
Jul 22, 2012
10
Hi everyone.

So an update on this issue. I went ahead and purchased a new EBCM (the electronic module, not the valves). I installed it on my own, and it was a fairly easy project, if you have a lift! Took about an hour, and could have been quicker if I knew what I was getting in to. I took the 3 larger bolts that holds the housing to the frame. That gave me enough wiggle room to get all 4 screws holding the ebcm to the valves. After I put it back together (making sure that the negative terminal was removed during the installation), I no longer had the door chime going off, and the information display no longer had "Service Brake System".

The ABS and Parking lights did stay on.

I took it to the dealer this morning to have them program the new EBCM. The brakes do work after replacing the EBCM, and before having it programmed. I drove it maybe 150 miles between those 2 happening.

The dealer just called me to say that they are done, but there are still issues. Apparently the tech discovered that there is a "fault in the B positive", and if I "were to hit a large bump, that it could set off the EBCM once again". Which makes sense, because my ABS issue was intermittent. The dealer told me to purchase a new junction block, and have it installed. They said that the ABS and Parking lights are now off, but they could come back on at any time now.

So, of course I am now worried that I need a new junction box, because there is a loose connection somewhere..... Which would possibly make sense as to why my headlights, maybe once a month, dim to almost going completely out!

Well, thats the latest with my gremlin.....
 

Mooseman

Moderator
Dec 4, 2011
25,472
Ottawa, ON
Which or what junction box? If it's just a loose connection, can't they just fix that? I saw another thread where a stealership wanted to replace a whole fuse box because one fuse connector was loose. All that was needed to be done was to twist the fuse blade a bit for a better connection.
 

Pittfan

Original poster
Member
Jul 22, 2012
10
The dealership tech said that it was a loose fuse. And he stuck something right next to the fuse to "hold it in place". I looked at it, and it wasn't loose at all.

For sure something is loose. Just moving the vehicle trips it. I am going to move the fuse box around to see if I can trigger it to go off. See if there is a loose connection. If not, I will check all of the ground wires. And if there still isn't anything, I am prepared to run a new wire from the fuse box down the rail to the ebcm. Eliminating any issues with the wire (if there is one).
 

Mooseman

Moderator
Dec 4, 2011
25,472
Ottawa, ON
If you grab my manuals, they have the wiring schematics (in nice colour too!). It could be the wire itself that's broken, frayed or corroded under the box. Knowing the wire colour would help. I would suspect more a bad ground connection.
 

Pittfan

Original poster
Member
Jul 22, 2012
10
There are 2 red cables under the fuse box that appear related to the fuses (near fuse number 33, for the ABS). They are in the same harness that connects to the under side of the fuse box. One looks like it would go to the ebcm, as I trace it.

I have been driving around with the fuse pulled out. That way I do not short out my new ebcm. The ABS and Parking lights stay on, but I do not have the door chime going off. When I got home today, I put the fuse back in the fuse box. Which will turn the ABS and Parking lights off. As they should be under normal conditions. I got in the envoy, and backed it up maybe 2 feet, and the the lights came back on (with the door chime). This is VERY intermittent.

So, I moved the vehicle another 2 feet, and the lights went back out. I put the vehicle in park. Got out, and went to the fuse box and shook it violently! The ABS and Parking lights did not come on. I shook the vehicle violently, still nothing.... I jiggled the 2 red wires under the fuse box, nothing.... I even looked at the ground wire on the fender. Took it off. Snipped some to make sure the contact was good, and put it back on the fender. No difference made.

Not sure what moving the vehicle has to do with anything. But that appears to be the only thing that will set it off. I can bounce the vehicle up and down all I want, but it won't cause the ABS and Parking lights to come on. It appears that it only happens when I actually move the vehicle.

Thanks!
 

Mooseman

Moderator
Dec 4, 2011
25,472
Ottawa, ON
That is so weird. The only thing that should happen if the ABS is affected when moving is a bad wheels hub or a speed sensor. Should not do anything to the interior lights :crazy:. Maybe somebody can chime in but what if it's the BCM that having problems since it does control the interior light? Or the EBCM is back feeding some sort of bad signal to the BCM to turn on the lights? They do talk to each other and the PCM. Just grasping at straws here, totally lost on this one. Would need a Tech2 while it happens to see what is happening and would need someone that really knows how to use it. And if it's a VERY intermittent problem, it can be difficult to get it to do it while trying to diagnose it (read: expensive per hour time at dealer).
 

Pittfan

Original poster
Member
Jul 22, 2012
10
I am leaning towards just letting this issue go. Not sure what to do with it. I have thought about replacing the entire power running to the EBCM from the fuse box, but not too sure that is going to have any affect... The issue is so random, it doesn't make any sense to me. Why is it that I can shake the vehicle so violently, and nothing happens. But I put the vehicle in gear, and move it 2 whole feet, and the thing lights up? I am half tempted to just leave the fuse out, pull the instrument cluster out, and remove the 2 light bulbs! Sure, it might prevent me from having any future issues displayed, but then again, the lights are on all of the time right now anyways.....

Frustrating.
 

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