'99 3500 4x4. The abs and brake light will come on randomly. I notice no change in braking function, I can power cycle the truck and lights with usually go away. How no idea where to start on this..........topped off the fluid level so its not that. Any help would be great, I dont really want to take this into the shop to be worked on.

 

brake light switch was my demon, but I only had abs light

 

maybe we can get to the bottom of this together... truck's Brake & ABS lights have been intermitent for well over a month now. They come on for a few seconds then go off but lately both lights no longer shut off. I have noticed the lights shut off temporaily when driving on a rough road or when running over a small pothole.

Here's a few more interesting twists...

1) When Brake & ABS lights come on, truck's speedometer becomes sporadic or simply reads 0 mph....

2) When ABS & Brake lights come on, windshield wipers will not work and/or become sporadic...

Searched the forums and found a few posts mentioning the speedo sensor... If this is strictly a speedo sensor issue, why are the windshield wipers affected!?

Someone tell me this is something else, I am not looking forward to pulling the truck's hub to get at the sos

 

wildbill, yours does sound like the speed sensor. Not sure about your '03 but the 2nd gens sensor is just on top of the diff on the rear axle. No disassembly of anything, just a single screw holding the sensor and it just pops off. Costs about $40 and takes about 15minutes to swap it out. Brake light/abs and no speedo points direct to the sensor. The wipers not working...not sure, might share a common power.

 

Your symptoms lead me to believe you have a loose or corroded ground wire.

 

Spent some time poking around under the hood pushing/pulling on things and lucky enough, happened to tug on a wire cluster which led back to a slightly loose and corroded ground screw! Uploaded a photo for better reference... its the ground screw touching the tip of the orange clamp (located on driver side fender rail).

 

Hope that cured your problem.
According to my factory service manual my '95s have 16 wires attached to a chassis or engine ground.
They're all over the place.
If you have a low amp short to ground that's not enough to blow a fuse and is usually caused by faulty aftermarket wiring or an accident it can cause electrolysis that corrodes your ground connections.

 

if that doesnt cure it. try checking brake fluid levels. recently had to put in new rear cylinders on my 99 24valve. same lights came on played with things for a week then it showed itself in a puddle of brake fluid under my tire.

 

Is the transmission slipping? when my abs light came on the transmission went out

 

Mine had the same or simular codes
but I didnt have ANY HEADLIGHT ISSUES

 

In hindsight the headlight issue may NOT have been much of an issue ... the more I think about it the more I believe it was just the normal headlight delay that occurs when shutting the truck off at night ... I could've swore the delay was really long in shutting down one night ... was probably just me being overly paranoid.