A couple weeks ago I was driving to work and noticed a grinding noise coming from the front passenger's side when I turned left. Put the car up on stands and I could feel the play in the front hubs. Truck as 175K miles on the original hubs so I figured it was past due to replace them.

The new hubs came with new ABS sensors installed. While replacing the hubs it looked like the wiring on one of the new hubs was compromised where it goes into the sensor. Since I had it all apart, I replaced the hub anyway. For the first 100 miles it was fine. It drove and steered much better, and the grinding noise was gone. About 100 miles in, the three brake warning lights and the traction control light all come on. I clear them with the ABS tool, but they keep coming back. The truck rode and drove fine, but the lights were all on. For clarity's sake, the brake and TC lights were not on with the bad hubs. I replaced the hubs because they were shot, not because of the lights. I assumed it's the compromised sensor wiring. I contact the vendor and they don't sell the sensors. No problem, they refunded the cost of the two hubs entirely, and told me to keep them. Ordered a new sensor from a different vendor

I go to install the new sensor and as I remove the bad one I realize that it is shimmed. There are seven very thin shims between the bad sensor and the new hub. The replacement sensor does not have shims. Vendor tells me they are not needed, so I do not install them.

So now I wrap up the install and connect the new sensor. Clear the codes again. Go to do a test drive. Start it up and lights do not come back on. Excellent! As soon as try to turn the wheel and move forward, the traction control engages, and the TC light comes on. Not excellent! Take my foot of the gas pedal and the TC disengages and the light goes back out. Every time I try to accelerate, it repeats. Soon as I lift the pedal it rolls fine and resumes accelerating. TC light goes out as soon as I lift the pedal. The three amigos have not come back on. I cannot really drive it like this. It is constantly stopping and starting. If I disconnect the sensor at the firewall connector, I can drive it fine, but all the lights come back on.

Based on the above, I am assuming that the previous sensor was bad, because all of the lights were on, and that was not the case before I replaced the hubs. Also seems like the ECU is now getting a signal from that side sensor, because the lights go out and the TC is wonky when I plug the sensor back in.

Did I screw this up by not installing the shims when I swapped sensors? Does his make sense that I am assuming it is still a sensor issue? Am I missing something entirely?

As always, thanks for all of your help.

 

I would say reinstall with the shims. The shims are likely to make up for over-milling of the mounting location on the hub.

 

I could've written this post myself. Reinstall with the shims, but you'll still probably have this problem. You just have to keep trying out new hub/wire combos until you finally get a good one. I went through a lot of them before finally having one with no errors or lights and it was specifically the AllMakes brand one from Rovers North.

 

I'm very interested in this as I've got this exact problem:

I installed new hubs years ago, but don't recall seeing any shims. Are you talking about shims where the sensor plugs into the hub? I don't recall taking out the sensor, so maybe I just never knew they were there. It seems like adjusting the shims may be helpful. Do you have any pics?

I just assumed that one of my hubs is bad and, based on the way that the traction control works, I wasn't sure if it was the hub to which the ABS is applying the braking or the hub on the opposite side. KEEP US POSTED!

 

Any update here?

 

cleaned and Re-installed the sensor with the shims. Nothing. Still engages the TC on acceleration. Any suggestion for the best brand sensor?

 

So, as an old mechanic, I've had a couple thoughts about this sensor situation, maybe helpful, prolly not.

It was common on quite a few models back in the day, to have VERY specific air gap tolerances between ABS sensors and their corresponding tone rings, as well as specific amounts of twists in the wiring per inch going to the sensors. I am not specifically aware that the Disco has this spec for it's sensors, or what it would be, but maybe someone else will know for sure. Otherwise, I would assume that the shims were necessary, and the reason you would have had shims in the sensor mount, is that gap, and it's correlating pulses and resistances, would have been preset to a certain range.

Also, pardon me if I am misremembering, but I thought I read somewhere that the hill decent mode for the Disco uses readings from the transmission and the ABS sensors to operate. I also believe that one of things that are relearned after clearing the adaptives with a Nanocom was the transmission shift points and abs braking info. So, with that in mind, I wonder if changing out an ABS sensor necessitates a clearing of the computers learning to reset and allow the system to relearn together with the new values.

Again, just some thoughts, maybe they help, maybe I'm misinformed and applying old knowledge inappropriately