These trucks had a TSB for a bad G110 ground, which would set a c0265 code, turning both the ABS and service brake lights on. Mine had these lights on intermittently, then all the time until I fixed the ground. It is located on the cab support just under the driver's door. Remove the bolt, clean the bolt, ring terminals, and frame real well, and reassemble. I found some undercoating between the frame and rings, some brake cleaner took it right off.