Another thought is the ABS mounting location subjects it to extreme heat from the exhaust/catalytic converter. Check out the ABS heat shield available from simple-engineering.comCheck the ground that is located on the inside of the frame right under the driver's side seat. Check if it's rusty or corroded. This can make the ABS throw errors and make gauges erratic.
I had this problem due to the underbody being splashed with salt/brackish water during king tides in Fort Lauderdale which accelerated corrosion and transfers electrolysis also. I thought my ABS was faulty. It was just the ground on the frame. Clean that before you look for more parts. *the ABS unit also crosses over into other GM vehicles.