I have been having some problems with my truck brakes, I'm out of ideas, hoping you guys can help.

problem 1) the ABS light comes on and dings everytime I start the truck, after about 30 seconds the light goes off. It will sometimes come back on again when I drive, maybe 15-20% of the time.

problem 2) while braking at slow speeds the brake pedal looses pressure breifly. The brakes work just like normal until I get down to about 10mph, once I get to that speed the brake pedal gets mushy breifly, I will press it a little further and the brakes act normal. THE WEIRD PART is that this DOES NOT happen if the ABS light on my dash is on, it only happens when it is not on.

I have taken both front wheel speed sensors off the hub and completely cleaned them, it did not fix the problem.

Do you guys have any ideas?? My only thought is that there is a problem with some component of the system that "thinks" my wheel is locking up when I get down to 10 mph causing the ABS to engage.

The odd part is that it doesn't do it when the ABS warning light is on. Is the ABS system bypassed when the warning light comes on???

"Mr Brakes" (heymccall) should have an answer for you by days end.

Premis...I had that condition in my '03 dually and it didn't go away until I changed the front hubs. It's your wheel speed sensors. Trust me!

As for your brake lights...there is a ground right under the drivers side floor plan on the frame. You'll see it as soon as you look under there. It's on the body mount bracket. Remove the bolt and clean the contact surface. Make sure ya got bare metal. Then clean off the loops of the wires and tighten it back down. There is a TSB for that and I just don't know the number of it. I'm sure someone will chime in with it.

Premis...I had that condition in my '03 dually and it didn't go away until I changed the front hubs. It's your wheel speed sensors. Trust me!

As for your brake lights...there is a ground right under the drivers side floor plan on the frame. You'll see it as soon as you look under there. It's on the body mount bracket. Remove the bolt and clean the contact surface. Make sure ya got bare metal. Then clean off the loops of the wires and tighten it back down. There is a TSB for that and I just don't know the number of it. I'm sure someone will chime in with it.

I did clean the ground bolt, forgot to mention that. Just to clarify, I'm not having problems with my brake lights, but the ABS indicator light has been coming on.

I just replaced the drivers side hub about 10k miles ago. I agree it could be the ABS sensor on the hub, is there anyway to buy just the sensor instead of shelling out 200 bucks for a new hub?

Sorry...I meant the brake warning lights on your dash cluster.

Yep! You sure can! Chances are that's all that's wrong though. The bad thing about just changing the sensor is that most times its being eaten up by worn bearing material inside the hub and the bearing is getting ready to let go.

If you have trouble getting one let me know.

Sorry...I meant the brake warning lights on your dash cluster.

Yep! You sure can! Chances are that's all that's wrong though. The bad thing about just changing the sensor is that most times its being eaten up by worn bearing material inside the hub and the bearing is getting ready to let go.

If you have trouble getting one let me know.

Sounds good, I guess I'll look towards that. I just had both sensors out this weekend, no metal shavings anywhere.

Is there a way to test them so I know which one is bad, or if they are bad? Maybe a resistance test? Any idea what they cost or where to get them?

Try gmpartsdirect.com. They are pretty close to what I can get them for.

I found them on GMpartsdirect but they don't have one listed for a 2500 4wd. Do you know if the 2wd or 1500 would be the same?

Sounds like we have about the same problem. My truck is showing code C0040. Right front speed sensor. I have a 2007.5 LMM 2500HD. GM told me I would have to replace the entire hub and could not replace ONLY the speed sensor. They also wanted $375. Not including labor. Sounded like a rip-off to me! Let me know what you find out.

To the OP, read this one http://www.dieselplace.com/forum/showthread.php?t=311628&highlight=abs+sensor for the Stutter in the brake pedal. The achilles heel of the sytem is that when the sensor is giving poor information, the lamp will not illuminate. That's your "skip" as you're braking. As for the lamp illumination, have a scanner read the ABS code(s). I'd suspect you'll get a communications error code, warranting either a reflash update, or replacement of your batteries, as low cranking voltage will also give a communications code.

As for the LMM, its essentially the same system. Lamp illumination will not occur, nor will that code store, unless the wiring loop is broken to that sensor. Inspect the harness at that corner.

Thanks so much for the info. I will have to have a look at that now! Hopefully I will get the problem tracked down. This has been bugging me for a couple months now.