Can anyone tell me how to check the link from the tach to the 'PCM'? I read a post that someone was having 'off' readings from his tach and it could have been the link between the gauge and the PCM. I have done the calibration a few times and it will drop about 300 rpm at random times when it stops. If it is a bad ground or a loose connection I would like to try and find it. Also could it be a bad ground on the cam sensor? The truck idles fine and runs fine, just a weird reading occasionally from the tach... I have an '06 1500 4x4 with the 5.7L. Thanks for any advice...