Archived ABS and Brake warning light on

[Sampson]

Started my truck the other day, both the ABS and the brake light stayed on. I tested the brakes, they work ok. Driving the truck gives me no problems. The lights just stay on. Are there any suggestions as to just what my problem might be? I tow a 30 foot trailer.



My truck is a 1999 with a pacbrake and a bluechip box. Both the ABS and brake light is on giving me the idea that it is an "electrical" problem someplace.

 

[B.G. Smith]

Could be a wheel sensor or the speed semsor in the rear differential. What year truck is it? bg

 

[cojhl2]

I had this on my 1990. According to the service diag it was the RVAL controller behidn the glove box.



Not true,, it turned out to be a shorted wire coming up from the rear diff sensor.



I drove this way for months before I finallly figured it out with the help of a paid mechanic.

 

[Sampson]

Where on the differential is the sensor located? I looked but could not find anything attached. Tomorrow I will get under the truck and see if I can spot any wires coming from the rear end. Thanks for getting the ball rolling.

 

[GAmes]

If you do a search you will find a large array of troubleshooting and fixes.

 

[p-Bar]

The sensor on the diff is also the for your speedo, if the speedo is not jumping around , I highly doubt that is the problem.

 

[Sampson]

p-Bar, that sounds logical. Could it still be a wheel sensor to cause the ABS and brake light to come on and stay on? I've checked the wires and electrical connectors for what I can touch, under the hood, they all seem to be good. Is the ABS unit the unit to the outside of the master cyclinder with all the hydrolic lines coming in and out of it?

Just a bit confused.

 

[p-Bar]

Have you tried resetting the system using a code reader? I have the same assumption that the ABS unit is the outer part of the master cylinder.





I did a search on the 2 gen here are the pages:

https://www.turbodieselregister.com/forums/search.php?searchid=1395980

 

[Sampson]

I have not attempted any reset. I will have to wait until after the holiday to do that. The dealership service department will be closed Monday and Tuesday. Thanks for the good advice. I do beleive the system works but the lights are on. When at the dealership I will ask them to identify the ABS unit for sure... then share the information with you. Thanks again and have a great 4th of July.

 

[B.G. Smith]

Where on the differential is the sensor located? I looked but could not find anything attached. Tomorrow I will get under the truck and see if I can spot any wires coming from the rear end. Thanks for getting the ball rolling.

The sensor is located on top and at the center of the differential housing. Mine came on one time when a bearing went bad in the differential and metal from the bearing collected on the sensor. I believe it is a Hall effect type sensor and is magnetic. My speedometer never quit working but it would jump a little once in a while. bg

 

[p-Bar]

Autozone or Kragen can't remember which ,will reset it for you "free"

 

[Sampson]

Hi Guys,

I should have responded to this thread sooner. Sorry. I replaced the sensor on the diff, all problems solved. Thanks to everyone.

Later,

Dick