where to start no stabiltrak or abs

[sick1166]

2007 4.8 tahoe while driving abs and service traction control and no stabiltrack all came on got to destination came out and was fine, This happened again but know its on all the time and was wondering where to start.

 

[sumo]

Start by pulling codes. Even though the lights not on, there still should be set in history

 

[Elmo]

Make sure master cylinder fluid level is full. Mine was low and I got that message after parking on an incline. No message when on level ground.

 

[sick1166]

pulled code
rear wheel speed sensor

 

[Mywifeshoe]

I know mine came on recently when I changed my rear shocks. There's a small plug for the abs on the rear driver frame rail right next to the top bolt.