Two warning lights, “brake” and “ABS” come on together when I’m driving and will go out when the truck is shut off. If I stop immediately when the lights come on and turn off the truck, the lights will not come on again. There is no apparent lose of brakes or other affects from the warning lights coming on. This has been happening for a couple years. They may come on an hour later or it may be a month later. Even going over very rough roads doesn’t cause them to light up. So, whenever the two lights come on, I stop, turn off the truck and they go out, then I restart the truck and resume my trip. Any ideas why this is happening?
If the primary brake warning light comes on, the ABS warning light comes on automatically.
This is because the ABS is warning you that if there’s a problem with the primary brake system, that ABS isn’t going to function.
So, if you can get the primary brake warning light to shut off, the ABS warning light will also shut off.
Have you had your brakes checked?
This era Chevy/GMC truck has a known history of tossing ABS/Brake warning lights. There are a couple of things you can check, but it is likely the ABS controller.
There is a ground under the battery box on the left side engine compartment. Take the battery out, take the box out, and then remove the ground and clean it really well- exposing new metal if need be. tighten it all back up and reinstall the battery.
Another ground to check is on the frame directly under the drivers door- towards the front of it. Do the same as above- take off the ground, clean it up real well, and reattach.
These have been known to help, but may or may not help you (they didn’t help mine any, lol)
Start by getting the ABS error code(s). Many new consumer-grade code scanners can read ABS codes. When I had this issue in my '07 Ram, the code came back as low fluid level. The sensor in the master cylinder reservoir was bad.