Hello everyone.

Help, I am pulling my hair out. I have a 2000 Bonneville SE that we bought new in 2000. It has been having a problem with the Brake, ABS and Traction lights all on. Oh yea, I should also say that my car has the Traction control option on it.

I have been having this problem for quite a long time. When it first came up, I am sorry, I forget the code that it threw. But when I checked for fixes, the top one seemed to be replacing the Electronic Control Module. I was unable to find a new or repo of it, so I found a used one and replaced the unit with that. I did not replace the ABS pump unit. This seemed to fix it for about 1 year, then it started to have issues again.

Again I was unable to find a new, repo, or rebuilt one, so I again purchased a used one. As before, this seemed to fix the issue. The lights went out and no code was thrown. But soon after, when my wife was driving, it would act like there was either low traction or that she had hit the brakes and the car was needing the abs. The car would for a short time active the abs for no reason.

I purchased again a used Electronic Brake Module and installed it. Then all lights stayed on and it gave the code U1040. I have been trouble shooting this issue now for over 1 month.

Thinking that there may be a break in the wires inside the wiring harness, I bit the bullet and spent all day yesterday chasing down the wires from the Electronic Brake Module. Our car had been very will maintained, and the harness did not show any obvious damage, and chasing the wires from the Electronic Brake Module from to the main wiring harness and then to the PCM did not find any damage to the individual wires. No damage to the wire insulation or any places that looked like the wire may have been broken inside the insulation.

One thing that I have not done was chase the wires back to the individual sensors at each wheel to see if there was any damage to any of those wires. I have in the past had an issue where something had kicked up from the road and cut the wires that lead to the rear left hand wheel sensor. I repaired that back then.

One of earlier codes showed a possible fix was replacing the ignition switch. I did that that also.

Here are my questions.

If it is the wires under the car leading to the sensors, should it not throw a code showing which sensor it having an issue?

If there was a problem with the pump itself, would it not throw a code showing problems with the pump? I did check continuity of the pump motor and it was found to have continuity. I also checked and the hot wire was hot.

Can anyone offer any advice or suggestions of what to try next?

Our car has around 170,000 on it and my wife is loves driving the car. I do not want to give up on getting this fixed for her. And I have to give up on the car.

Also A little history on the car. It have been problem free except for normal things. I had to replace the starter a few years ago. And I have had to replace the fuel pump. When the car was still under warranty, we had an issue with the transmission. The dealer found that there was a notice out at that time about repairing the transmission. Sadly, the dealer when they made the repair, did not replace all of the parts the manufacture said needed replaced. That caused a new issue that ruined the transmission. This caused us to have to replace the transmission with a GM factory rebuilt one. Back a few years ago, we started having transmission problems again and replaced the transmission again with another rebuilt one. So far so good and that one.

About a year ago I had issues with the ABS and Traction Control lights coming on randomly. The Track Loss light would sometimes randomly flash and the ABS would activate for no reason when stopping. Turned out to be a bad front wheel bearing. Changed the wheel bearing and problem went away

Thanks Louie. Did the computer throw any codes? How did you figure out the bearing was bad?

Well it start with the random ABS activation and "trac loss" light coming on. Then I started getting a wheel grease smell after driving for a while. Then the bearing moan started (probably because it burned all the grease out of the bearing).
I don't have a scanner to read body codes. The left front bearing was changed at the previous inspection when I was told it was bad. Car didn't drive any different with new one, and I know the guy put the cheapest one in. The left front was chattering when the ABS activated. I read if the axle nut is over tightened, it preloads the bearing and kills it. The first sign of a bad wheel bearing is usually ABS light issues.
Changed the bearing myself and haven't had issues since.

without a proper tech 2 scanner, I would first check the wires for the abs plug at each wheel - unplug and check for corrosion inside the connector. the sensor could be wonky, but tha'ts inside the bearing/hub assembly.
you can always remove the abs relay and drive with no abs/traction and ignore the lights

_________________
poverty forces one to do unorthodox things

2000 SSEi
past rides:
1996 SSEi
1992 GTP
1987 Grand Am

I was having the same problem this spring and spent the summer working on the Bonneville changing out parts. It was one of my wheel hub/bearings. If you can do brake and suspension work, it's easy to dig one step deeper and change your hubs. All my warning lights cleared as soon as I plugged the new one in.

Timken is the recommended brand.

(If you wanted to be sure before doing the work, you could jack up the car, take the wheel off, and plug the connector into the new hub to see if everything clears before you tear everything down and replace it)

_________________
2003 Pontiac Bonneville SSEi (L67) - Galaxy Silver Metallic
1996 Chevrolet Camaro (L36) - Sebring Silver

I have a cheap code reader, it is telling me the U1040 code. If it was one of the wheel sensors, would it give that code? Or would it be a specific code for that wheel?

you may be on the right track...........https://www.engine-codes.com/u1040.html#fix

_________________
poverty forces one to do unorthodox things

2000 SSEi
past rides:
1996 SSEi
1992 GTP
1987 Grand Am

Latest update on trouble shooting this. I purchased a Automotive short and open finder to track the wire circuits. So far, I have determined that there are no faults in the wires that takes the data to the PCM and there are no faults in the wires to each wheel sensor. I was trying to track the wire to the fuse box under the rear seat. If I check the continuity of it using a electric tester that I have, it does not show continuity even when the ignition switch is in the on position and I hold down the brake pedal. I am not sure if the relay is only energized if the Brake control module determines that it needs to activate the ABS or not. Going to research this a bit further. I tried using the Automotive short finder and it found that the wire was ok from the Brake control module through the wire harness to the back of the engine department. But when I check at the back fuse box the signal does not make it there. Maybe that wire is my problem. I checked under the car and could not find any wires running to the back of the car under there. I can only assume that it most go through the firewall and run in the interior of the car to the back seat fuse box. Any ideas of where the wire harness may travel inside the car?

U1040 is a loss of communication code, doesn't really help you. If it were a problem with a specific component it would tell you that (C1234 Right Front Wheel Speed Sensor Input Signal Missing).

Have you checked for power going to the EBCM? Are you sure the used replacement was an exact replacement? There are many different variables with the EBCM's.

*edit* The cars wiring runs down both sides of the car under the carpet/seats, but don't worry about that, I really doubt your problem is there. I'm guessing you are going to have a wiring problem in the main engine harness between the underhood fuse box/pcm/ebcm.

_________________
Andrew - owner/operator of Bonnevilles Unlimited

2004 Bonneville GXP | 60k | White Gold Tricoat | custom built supercharged 3800 hot rod | garage queen
1997 Corvette | 55k | Silver Metallic | Z06 wheels | Date-night Hauler/Parts runner
2014 Town & Country Limited | Cashmere Pearl | 95k | Family Hauler
2002 Ram 1500 Quad Cab Sport | Black| 260k | Official Bonneville Hauler

yes you need a tech 2 class of scanner and it will pinpoint the issue

maybe worth the 50 - 100 bucks for a shop to scan an give you printout.

_________________
poverty forces one to do unorthodox things

2000 SSEi
past rides:
1996 SSEi
1992 GTP
1987 Grand Am

Again, a Tech2 isn't going to tell you anything special on this one unless you know how to use it as a diagnostic aid. A U1040 is just a lost of communications in the serial data line. All of the modules on the car communicate via this serial data line (purple wire) and they are all daisy chained together. There is either a break or short in the data line, or another module on the system is causing havoc on the system. I once had an airbag module that failed and took out the communication to the EBCM only, even though they aren't even close to each other on the data line order.

_________________
Andrew - owner/operator of Bonnevilles Unlimited

2004 Bonneville GXP | 60k | White Gold Tricoat | custom built supercharged 3800 hot rod | garage queen
1997 Corvette | 55k | Silver Metallic | Z06 wheels | Date-night Hauler/Parts runner
2014 Town & Country Limited | Cashmere Pearl | 95k | Family Hauler
2002 Ram 1500 Quad Cab Sport | Black| 260k | Official Bonneville Hauler

Just had a car come through my shop with this exact problem. U1040 in the PCM and C1248 and C1254 in the EBCM and all lights on the dash. I could still communicate with the EBCM with my Tech2 but the codes kept popping up. It was a corroded ground connector for the EBCM ground which is on top of the transmission next to the shifter linkage.

_________________
Andrew - owner/operator of Bonnevilles Unlimited

2004 Bonneville GXP | 60k | White Gold Tricoat | custom built supercharged 3800 hot rod | garage queen
1997 Corvette | 55k | Silver Metallic | Z06 wheels | Date-night Hauler/Parts runner
2014 Town & Country Limited | Cashmere Pearl | 95k | Family Hauler
2002 Ram 1500 Quad Cab Sport | Black| 260k | Official Bonneville Hauler

Thanks folks.

I'll try to answer some of your above comments.

I tried to order EBCMs that matched my car's options. It has the traction control so I ordered the one that has with active braking/traction control. I think that was J29. My car does not have the steering option

I had figured the purple wires were the ones for the data lines. I tracked them to the PCM and did not notice any breaks or kinks in them that made me think that the wire was broke inside.

I do have power at the connector to the EBCM.

I have checked the fuse under the back seat and it checked out.

Is it possible one of the relays under the back seat is bad? I could not determine which one may be for the brakes

I purchased one of the fault circuit testers. When I checked each wire for the sensors at the wheels it tested ok. When I tried testing the wire that goes to the fuse under the back seat. I could get it to work all the way to the firewall. When I checked at the back seat though, the signal did not make it to there. If I was chasing the right one that is. It was a brown one. Is that the right one that should go to the back fuse?

If I put the tester on the wire coming from the back fuse box, I was able to get a signal all the way to the front fuse box, but I am thinking the signal was following the hot wire, but not sure. I could not get a signal at the EBCM when testing from the back fuse.

I am going to keep chipping away at this until I get it figured out. My wife loves driving that car.

Does anyone have a way to check what options I should make sure the EBCM that I have it correct. I purchased one that said it was the one with the active brake control/traction control. My car's VIN is 1G2HX54K3Y4289522.

I did unbolt the ground connector at the top of the transmission. I looked the connector end over to see it it was corroded, but did not check the wires. The one you have a picture of looks like the wires are corroded but the connector does not look bad. On mine the wires are covered with insulation. Did you have to take the insulation off to discover the corrosion? Maybe I should re-investigate that and see if my wires are corroded inside the insulation. Just a thought

All help appreciated!

Yes I had to remove the insulation to see the corrosion. I would look further into this.

_________________
Andrew - owner/operator of Bonnevilles Unlimited

2004 Bonneville GXP | 60k | White Gold Tricoat | custom built supercharged 3800 hot rod | garage queen
1997 Corvette | 55k | Silver Metallic | Z06 wheels | Date-night Hauler/Parts runner
2014 Town & Country Limited | Cashmere Pearl | 95k | Family Hauler
2002 Ram 1500 Quad Cab Sport | Black| 260k | Official Bonneville Hauler

Finally found out the problem. Two of the 3 bolts holding the fuse box under the hood down were lose. I tightened them and this issue was fixed, and also a new problem I had of the starter not turning over when turning the key switch. I suggest anyone having any issues that seems to be wiring related to check the fuse box bolts and make sure they are tight

Good catch. Those three bolts tighten the three harness blocks to the fuse block, if they are loose enough there could be weak or intermittent connections from the harness to the fuse block.