2nd Gen Non-Engine/Transmission Brake light and ABS light on

[ronco]

Started home last Tuesday from town and noticed the Brake and ABS lights were on. I checked the parking brake and noticed that the intensity changes with the parking brake, but that's not it. This evening, I pulled out my vacuum pump and tied it in to the vacuum manifold under the hood. I pulled about 25" of vacuum and waited a moment. The vacuum did not leak down, so I continued. I started the truck and watched the vacuum gauge rise to 28" of vacuum. The warning lights still did not go out. Fluid level in the master cylinder is good. I checked the ABS fuse and replaced it, just in case. Still have both lights on. Tomorrow, I will jump out the low vacuum switch on the fenderwell to check it out.



Meanwhile, the brakes feel as good as normal. I do have the larger wheel cylinders installed (last year). Does anyone have a suggestion?



If the ABS fails, will it cause the "Brake" light to come on? If the hydraulic brake switch senses a problem, will it also cause the ABS light to come on?



TIA



Ronnie

 

[Fogie]

Some have found the sensor on the top of the rear differential to be the culprit. I could be dirty, or it could be bad. Others have found a bad wire near that sensor. If you have front ABS check those sensors as well. On my 99 I found the brake light switch on the steering column was bad. I followed the instructions that came with the new switch... and it cleared my problem. Good luck on yours.

 

[Casey Ray]

Had the same problem about 2 weeks ago, bad wire on the front ABS sensor. Replaced ABS and now all is well.



Casey

 

[ronco]

Thanks for the suggestions. I only have Rear Wheel ABS.



Ronnie

 

[CCutshaw]

When my abs sensor went out last year (on the rear-end) it turned on the abs light and speedometer would not work below 30. Also check the combination valve to see if it's stuck.

Calvin

 

[Tom W]

I had this happen last week. Sensor on top of the differential - $40 from dealer. The brake line support is fastened to the sensor mounting bolt. Use 9/16 and 1/2 in wrenches to get loose. New sensor comes with a pigtail - female wiring connector faces opposite direction and old wiring is not long enough.

 

[DavidC]

I believe up to 99 the Vehicle speed sensor in the trans. operates the speedo. The ABS problem is likely the sensor in the rear differential. Should ohm at approx. 1800-1870 if it is good. Usually reads open when bad.



Dave

 

[RHARVEY]

This problem only shows up when I am puller our travel trailer. . They dont stay on very long at a time... and its doesnt happen all the time. .



Rick

 

[Skydiver]

After changing my front brake pads these lights will stay on for 2 days.

Was told it was some kind of sensor in the abs that detects dirty brake fluid.

Is that true?

Tim

 

[B.G. Smith]

After changing my front brake pads these lights will stay on for 2 days.

Was told it was some kind of sensor in the abs that detects dirty brake fluid.

Is that true?

Tim[/QUOTEt] Don't think so. When you replaced the pads, you had to depress the caliper pistons to get the new pads in place. Because you had to depress the pedal a couple of times after the new pads were in place to have a solid pedal, the combination valve probably became offset which set the light. When the pressure became the same to the rear and front brakes, the valve re-centered and the light went out. bg