Archived ABS light/brake light after brake job...

[-gtsm-]

Hi Folks,I rebuilt the brakes in the truck in my sig. 600mi. ago. new everything from the hard lines to the wheels,and I thought everything was fine until 600mi. after and my abs and brake light have come on. I read lots of posts before doing the job and thought I had bled the brakes sufficiently but I suspect that because I have 4-wheel abs and the associated hcu's and such that something still had air in it causing the pressure differential switch to activate and set a code causing the light to come on. I have checked for codes w/a scan tool but I don't think I can see a code w/out a DRB II tool. I have tried rebleeding the lines and also disconecting the batteries . I am picking up a new hose trailer wednesday and need to figure this out asap. I don't think this is a speed sensor issue although it is possible. Does anyone have any input such as verifying diff. pressure switch position,etc. My Haynes manual says that on 97 and later trucks w/ abs this needs to be done at the dealership , but after paying $1700 for a clutch job recently(I wasn't home to do the job myself) I am reluctant to take it in. I will be working on it all day and checking this post for replies so if you have any ideas I am listening. Thanks

 

[GAmes]

I don't think the present problem is related to your brake job. If there was air in the lines it would have shown up immediately. Have you tried unplugging your brake controller? If that makes the lights go out check the wire harness plug behind the front left wheel for water. Do a search on this subject and you will find other fixes.

 

[tractorface]

Had same problem

It is common for the speed sensor on top of the rear differential to cause the ABS and brake light to illuminate. You can try pulling it out and cleaning it but I'll bet if you replace it your problem will go away. Not an expensive item and easy to change. Very common from what I have read

 

[-gtsm-]

gonna go unplug my controller and also check rear sensor,let you know what I find. thx

 

[-gtsm-]

unplugging brake controller didn't work but thx anyway,I took the sensor off and cleaned it and I also checked it w/ a multimeter and got no resistance. I am going to replace it on the truck and recheck it with the meter . Seems like I read that it should have like 1. 8ohms or something but should not be open. If it is open when it is on the truck maybe I should replace it. I didn't suspect this part because of the recent brake job... if there is one thing I have learned about troubleshooting is to look at recent work/modifications as the most likely culprit.

 

[tractorface]

There is a "ring" on the differentioal that drives the speed sensor also. I agree with your theory that it is probably something you did but I have heard a bunch of people with your problem and its usually the speed sensor.

Good Luck

 

[-gtsm-]

Still no resistance w/sensor installed... i'm on my way to the dealership. thx

 

[-gtsm-]

just called dealership... part for 4x4 not in stock(part#56028229ab)she was surprised cuz they sell alot of them. I asked if it was a different# for 4x4,or 4/wheel abs and it was different for 4x4. gonna pick it up in the morning $37. 50 + tax

 

[-gtsm-]

Installed the sensor and problem is fixed! also I checked the resistance of the new sensor and it was 1. 89ohms this should help anyone who is troubleshooting their sensor ... if it reads 0 ohms replace it. I still can't believe that my problem wasn't related to the brake job,But I'm happy. Thanks again for your help.

 

[Andy Redmond]

Sometimes after a through engine bath the connectors that connect to the combo valve under the master cylinder will get some moisture in them that a shot of compressed air and dilectric grease of wd40 then the grease will solve.



Glad you found your problem. Depending on temps I've seen as little as 8/10ths of an ohm of resistance and it still work fine.



1. 4-1. 8 is a good reading!



Good luck

Andy