This seems to be a common problem with the Silverados. ABS sensor failed on one of my wheels causing ABS to activate at braking speeds under 5mph. This may or may not be life-threatening but it is a safety issue if brakes are not operating correctly under load. There areYouTube videos about how to replace the ABS sensors, but they are expensive. For me, it is at least worth trying to clean them first as some people online have said corrects the issue. A TSB was issued about this to snow belt states as well.

abs and brake lights came on while driving as well as tranny slipping. after diagnostic check was told vehicle speed signal was missing witch caused warning lights and tranny slippage. I had replaced vehicle speed sensor switch 2 months prior. Was told the wiring was probably bad.Before all this I received recall notice from Chevy specifically stating a problem with speedometer cable.The 2004 Silverado does not have a cable.It has a vehicle speed sensor, which I replaced for 40 dollars. It controls your speedometer and a variety of electrical operations.My question is :Is it a bad instrument cluster or simply bad connections in wire? After test, code was cleared, no abs or brake lights or tranny slippage but still have speedometer problems. I still have to check wire. Chevy has created own problems and I question their ethics.