Brakes Hard Left

[wellswa]

Well, I finally found an ABS module for my 2004. I installed only the electronic portion of the unit. Only took about two hours all said and done. Started the engine after finishing the job and walah, no more ABS light or Traction Control light on the dash. No more warning messages either. Took the car for a drive and my cruise control now works as well, yahoo! Took the car out the next day for a 10 mile short ride and on the way home the left front wheel applied the brake real hard for a split second and then released then the Traction Control light came on. I got home shut the engine down and restarted it and the light did not come back on. I checked the car with a scan tool for DTC's but there were none. I read on here about a plastic clip on the steering column sensor that could be the problem but it turns out that fix was for model year 2005 thru 2007. My 2004 doesn't have the clip. I unplugged the wiring harness from the steering column sensor and plugged it back in to no avail. The car still brakes hard to the left occasionally when I drive it. I tried turning off the traction control feature before I start driving the car and it did not do after that. Is there a fix for the 2004 model year for this problem or do I just need to turn off the traction control feature before driving the car? Thanks for anyone's help.

 

[RandB]

Sounds like the ABS is applying more pressure to the left brake and/or your new to you ABS module has issues. I would bleed your your system and see if that helps.
Also, do you have a Tech2, as that has a bunch of useful ABS features.

 

[wellswa]

Well, I was driving the car yesterday and after about 25 miles the left front wheel locked up on me at low speed without applying the brake pedal . This time the traction control light did not come on. I went to take off from the traffic light and it locked up again. I was able to get the car off the main road and into a parking lot where I shut the engine down and restarted it. Then I disabled the traction control with the button and drove the car home. I am at the point where I don't trust driving the car anymore. Ugh.

 

[nvme]

You might want to try removing the #27 fuse under the hood (60 amp) which disconnect the ABS function. The DIC will display a warning something like ''max speed 80 mph'', I think that is to tell you no ABS because we all know that today on the freeway you have to exceed the warning in order to keep up with the traffic. That should relive that left front wheel braking problem so you can still drive the car until you get the problem fixed.

 

[wellswa]

Well, I hooked up a Tech 2 scanner to my XLR today and I did find a DTC stored. It is U2108 "Lost communication with ABS TCS system" anybody have any ideas about this code? ABS = Antilock brake system, TCS = Traction control system.

 

[RubyRod]

Since you replaced your ABS module you may have a connector problem. Dirt or a bent pin on the connector that attaches to the wiring harness from the engine bay. You'll probably need to remove the ABS unit again to check the pins. If you don't see any bent pins try cleaning both the module pins and harness connector pins with contact cleaner. Let them air dry for a few minutes and then reconnect things. If this doesn't help it's likely that your "replacement" ABS module is bad. Not a happy thought but I think that's most likely.

The communications DTC is telling you that either the Engine Computer or the Body Control Module is having problems communicating with the EBCM (ABS module). It might be one of the other computers in the car that's having connection problems with the ABS but the ECM & BCM are the most likely. There is a pair of serial communications signals (wires) called CAN Bus (or what GM Calls High Speed LAN in my wiring diagrams for the car). Since you didn't see these problems before replacing the ABS module I doubt the problem is with the ECM or BCM.

You claim you "only replaced the electronic portion of the unit". I suppose you mean you separated the electronic module from the hydraulic module from the "replacement" unit and attached it to your original hydraulic unit. I hope it doesn't mean that you opened the EBCM module and replaced on the circuit board.

Oh. Did you disconnect the battery BEFORE removing the ABS module the 1st time? If not it's possible that disconnecting the ABS wiring harness may have caused one of the other computers to go into a degenerate state. I met someone with an export XLR who disconnected his headlights to perform a repair and when he put things back together he was getting several codes and idiot lights. Turns out disconnecting the headlights with the Battery connected upset the BCM (I think) and it put it in a degenerate state. He had to find a shop with a scan tool and enough knowledge of the car's operation to track down the code/parameters in the BCM and correct it. It can probably be done with a Tech2 as well but you have to understand what to look for and how to correct it. Changing the computer module memory contents is risky. Here's hoping that's not your problem. Based on this guy's headaches I now disconnect the battery BEFORE disconnecting any wiring connectors in the car. Maybe I'm paranoid but better safe than sorry.

Good Luck

 

[wellswa]

Thanks for the reply. I did disconnect the battery before I did any work to the car. I was told that by someone on here long ago. I did just replace the electronic module (not the circuit board) on the unit, I didn't disconnect the hydraulic portion of the unit at all. I have since found out that I had a seized slide pin on my right rear caliper. I fixed that, checked all the calipers and pads and found no other problems. I then flushed the old brake fluid using a pressure bottle system and then performed the brake bleed procedure using a Tech 2 scan tool. I performed the ABS bleed procedure as well. I took the car for a test ride and again after about 15 miles of driving the ABS applied the brake to the left front wheel momentarily, the traction control light came on, and then the car drove normal the rest of the way home. I taking it to a mechanic on Monday that is supposed to know these cars pretty well. He is going to try and program the ABS module using some GM software. He is not sure that is going to work though as he has never heard of a problem like this one. Just my luck.

 

[RubyRod]

When I was shopping for XLRs I drove one with well over 100k miles and plenty of issues. I always test the ABS operation when I shop for cars. When I tested the ABS on this particular car the ABS didn't work. No idiot lights or messages but no ABS function. After bringing the car to a stop I accelerated briskly and when I did the steering wheel wrenched out my hands first with a severe turn to the left followed by a severe turn to the right. The force was enough that I couldn't overcome it. Luckily I did this test where there was no traffic so I didn't hit anything. But it was a come to Jesus moment. Again no idiot light or messages during this "maneuver".

I assumed the problem was with the steering rack. I never gave the ABS a thought. But your description sound earily similar to what I went through. Maybe I should be more concerned about ABS failures in the future. I would think that if the ABS module had problems that the ABS just wouldn't work. I can't understand why it would lock up just one caliper. Seems like an extremely dangerous failure mode.

Hmmmm... I wonder if maybe one of the wheel sensors is bad and the ABS module thinks the wheel is slipping? That might explain why it's applying the brake. Although I'd think there'd be a code indicating a wheel sensor problem. Maybe not.

Let us know what you find.

 

[xlrlist01]

Well, I finally found an ABS module for my 2004. I installed only the electronic portion of the unit. Only took about two hours all said and done. Started the engine after finishing the job and walah, no more ABS light or Traction Control light on the dash. No more warning messages either. Took the car for a drive and my cruise control now works as well, yahoo! Took the car out the next day for a 10 mile short ride and on the way home the left front wheel applied the brake real hard for a split second and then released then the Traction Control light came on. I got home shut the engine down and restarted it and the light did not come back on. I checked the car with a scan tool for DTC's but there were none. I read on here about a plastic clip on the steering column sensor that could be the problem but it turns out that fix was for model year 2005 thru 2007. My 2004 doesn't have the clip. I unplugged the wiring harness from the steering column sensor and plugged it back in to no avail. The car still brakes hard to the left occasionally when I drive it. I tried turning off the traction control feature before I start driving the car and it did not do after that. Is there a fix for the 2004 model year for this problem or do I just need to turn off the traction control feature before driving the car? Thanks for anyone's help.

That clip should be fitted to the 2004 too. The early cars did not have it fitted as a (bad) deliberate choice. I have an idea it is a free fix at Cadillac. well, it was!
(PS 'voila')

 

[RubyRod]

I think the clip you're referring to is used to hold an electrical connector together under the steering column if the integral latch breaks. I installed one on my '05 when I was having no end of problems with "rebuilt" steering racks. If the latch on this connector is not broken the clip adds no value. If you search my posts for it you'll see my pics associated with the clip. It's more bother than it's worth IMHO.

 

[wellswa]

I did buy the clip for my 2004, but when I went to install it there was not one on the steering column. It is a different connector altogether on my XLR.

 

[xlrlist01]

I did buy the clip for my 2004, but when I went to install it there was not one on the steering column. It is a different connector altogether on my XLR.

This is a long time ago.
IIRC, the connector could lose connectivity if you changed the steering column position on a regular basis. If you set the column to retract out of the way when you exit, then it is much more likely problems will occur. If you keep the column in the same position all the time, then it wasn't much of a problem. The fix was to put in this 'clip', it is a comb shaped thing that keeps each connector firmly engaged in the right position.
But, we are talking over twenty years ago.

 

[wellswa]

Well, the XLR is in the shop now. I found a mechanic that knows these cars pretty well. He said that the EBCM (ABS) module needs programming in order for my car to recognize it. He has since told me that he cannot do it any longer because GM has changed their software to where it is no longer possible to reprogram a used ABS module in a different car. Now he is going to try and have my old module repaired and then reinstall it in my car. I'm keeping my fingers crossed but I doubt it can be repaired. I have a GM TECH 2 scan tool, is it possible to program the module using it?

 

[RubyRod]

If your mechanic isn't able to have the module repaired and he is unable to program it to match your car try contacting Module Masters in Idaho. Maybe they can repair it or reprogram it, maybe not. But if all else fails ask to speak to (email) one of their repair specialists. I had an email session with one of their specialists when I was sorting out my FPCM problems. They might be able to tell you how to program the "new" module. It's worth a try.

 

[wellswa]

Thanks for the info. I'm waiting to hear back from the shop.

 

[xlrlist01]

Well, the XLR is in the shop now. I found a mechanic that knows these cars pretty well. He said that the EBCM (ABS) module needs programming in order for my car to recognize it. He has since told me that he cannot do it any longer because GM has changed their software to where it is no longer possible to reprogram a used ABS module in a different car. Now he is going to try and have my old module repaired and then reinstall it in my car. I'm keeping my fingers crossed but I doubt it can be repaired. I have a GM TECH 2 scan tool, is it possible to program the module using it?

Assuming your Tech-2 was brought fully up-to-date, then surely it should be able to update any module? The whole point was that it was a standalone tool. Later GM changed to the online system.
I don't know for sure the situation with your EBCM, but what is there to program into it? If it came from a 2004 and is put into a 2004, then I was under the impression it should work. And, from your symptoms, it very nearly does work. If it needed to be reprogramed, would it work at all?
I don't know enough about this to be able offer solid advice.

 

[xlrlist01]

I performed the ABS bleed procedure as well. I took the car for a test ride and again after about 15 miles of driving the ABS applied the brake to the left front wheel momentarily, the traction control light came on, and then the car drove normal the rest of the way home.

The application of the brake in this situation is to correct a loss of control, ie a 'skid', or before a true skid develops, to reduce a violent change of direction.
There is a sensor that reports angular change, better 'rate of angular change', I forget its correct name (could be 'yaw' sensor). If that sensor erroneously reports a sudden change in direction, the EBCM will attempt to correct the situation. Ie, what proof do you have that there is anything wrong with the EBCM at all?

 

[xlrlist01]

Assuming your Tech-2 was brought fully up-to-date, then surely it should be able to update any module? The whole point was that it was a standalone tool. Later GM changed to the online system.
I don't know for sure the situation with your EBCM, but what is there to program into it? If it came from a 2004 and is put into a 2004, then I was under the impression it should work. And, from your symptoms, it very nearly does work. If it needed to be reprogramed, would it work at all?
I don't know enough about this to be able offer solid advice.

Update.
I asked my Tech how the Tech-II worked to update a module (when the Tech-II was the current GM tool). (It was a long time ago, so this is slightly hazy.)

1/ Step 1, plug Tech-II into the car. Go through the steps as instructed re the module. This will cause the Tech-II to note certain information about the module.
2/ Step 2, disconnect from car and connect to 'something', (a PC with an internet connection and GM account) and go through the process of the Tech-II requesting the latest firmware from GM.
3/ Step 3, the Tech-II is loaded up with the new firmware, disconnect.
4/ Step 4, reconnect the Tech-II to the car and follow the instructions to load the new firmware into the module.

(There was a similar process to update the Tech-II itself.)

The exact instructions might be different in detail, but the basics are that the Tech-II picks up some relevant information, that gets passed to Cadillac, the necessary file is downloaded and put into the Tech-II and the Tech-II loads it into the module. Ie, the Tech-II does not come with all the module firmware pre-loaded in it, the Tech-II has to fetch it from GM each time it is needed; which makes sense given the firmware is being updated.

The latest GM system (GDS-2?) is slightly smoother in that it is both connected to the car and to Cadillac at the same time, so the steps to move away from the car and back again are no longer required. The current system can update any year module, certainly back to the mid-1990s, with some very specific exceptions (which are not XLR ones). Also, the current system emulates a virtual Tech-II; while it works, my Techs prefer to use an actual Tech-II for most tasks where a Tech-II was the proper tool at the time, they find it easier and more reliable.

HTHs.

 

[wellswa]

Well they're making some progress on the XLR brake issue. They tell me they put in a brand new ABS module they had built by some firm and it comes with a warranty. When I get the car back I'll ask about the company that provided the unit and post their info on here, maybe it will be of use to someone else. The mechanic says the brakes are no longer locking up but now the car is throwing a code for the Yaw Rate Sensor. He checked the sensor and it is working fine. He thinks it may be a connection issue. He's looking into it. More to come.

 

[mickeytee]

When the abs module is not working it will throw a code for the yaw as its not computiing the signal