Why is my 2008 Chevy silverado abs light on?

While there are a few different reasons that Your 2008 Chevrolet Silverado's ABS dash light would illuminate, they typically (but not always!) have to do with a component in the ABS system. The most common causes are a failed wheel speed sensor, a defective ABS module, an ABS system in need of a specialized ABS brake bleed, or a broken tone ring on the wheel hub assembly. Hands down, the most common cause You'll see is a broken or d***y wheel speed sensor. Whatever Your case may be, it's prudent to check Your Silverado with an OBD-II tool capable of reading ABS codes; with it, You'll be able to pinpoint Your diagnostic issue. If it is indeed the wheel speed sensor, this diagnosis should point You to the correct wheel.