ABS Light

You're going to have to use a scanner to communicate with the module. There will be an option for 'ABS' on the scan tool. You'll have to start there. I have NO WAY to know which way to steer you without getting the info from the module. There's really not too much involved in the ABS system so, usually, they're pretty easy to diagnose. If the ABS light is ON, there's a code somewhere in the ABS module. It will tell you if it's a LF wheel speed sensor or RF, or vehicle speed sensor, etc. Get that info and get back with me and we'll fix it!

No you can not. They do not have the proper equipement to scan other modules.

He's right, don't take it to Autozone. And, if you do, don't buy the parts they're going to try to sell you yet. It'll have to go to a shop that has a decent scanner to access the ABS info. The scanner will tell you why the light is on. Without that info, we'll just be throwing parts at it til we get it right. When you DO get the problem fixed, the light will go out on it's own when you start to drive the truck. It runs a 'self test' each time the truck is started. If it's a wheel speed sensor, and the light goes out when you start the truck, it will come back on as soon as you start to drive the truck, when it monitors the wheel speeds. Some scanners will let you watch the speed of each wheel as you drive it. Mine is an OTC Nemesis and it will do it. I wish I could help you more but without access to the ABS info, it's difficult. But if you DO take it somewhere and get that info, I'll be glad to help you more.

The yellow ABS warning light will not cause the red Brake light to turn on, but the red Brake light will turn the yellow ABS light on. That's because the ABS Computer only knows something is wrong with the base brake system but it doesn't know what. That problem could result in an inability to run the anti-lock function properly.

That means you need to look at the red warning light, and there's only three switches at most that affect it. The first, if your truck has it, is a low-fluid level switch in the master cylinder. If the fluid is low, do not fill it. Add just enough to turn the light off. The fluid is low either because there's an external leak that must be addressed or the front disc brake pads are worn and need to be replaced. Replacing worn brake pads requires pressing the pistons back into the calipers, and that pushes all the brake fluid behind them back up into the reservoir. If a do-it-yourselfer or inexperienced mechanic has previously filled the brake fluid, it's going to overflow and run all over creating a mess, and damaging any painted surfaces.

The second switch is for the parking brake. Be sure the pedal is releasing fully. The last switch is the pressure-differential switch. That may be in the hydraulic controller for the ABS system, otherwise it is in the middle of the brass combination valve that sits on the frame rail right under the master cylinder. On vehicles without anti-lock brakes, you can follow the two steel lines from the master cylinder to that valve. Simply unplug that switch to see if the red warning light goes off. If it does, one of the two hydraulic systems didn't build pressure as fast as the other one. Typically that's due to a leak. That valve is spring-loaded on GM and Chrysler vehicles but sometimes it sticks. A quick hard jab on the brake pedal usually releases it.

The mechanic needs to list the specific fault codes, otherwise that's like your doctor telling you, "well, we ran some tests". Wouldn't you like to know the results of those tests?

Again, an ABS problem won't turn on the red "Brake" warning light. If that one is on, look at the three things I mentioned earlier. You can simply unplug each of those three switches to see which one makes the red light go off.