Erratic speedometer/tacometer
 

Does the ABS brake system have an effect on the instrument gauges of the speedometer and tachometer? The ABS light is on and both speedometer/tachometer are not working properly.

They should not be related. What year is your truck? There was a recall on vehicles from 2003 to 3006 because of faulty steppers for the gauges. If your truck falls in those years check with your dealer to see if your truck is under the recall.