Tachometer
 

Help please, my tach stopped working after getting my truck buried in a mud hole. It is 2001 2500 HD 8.1
I'm not sure if there are any wires underneath the truck that may have gotten damaged? I am not sure where to start.
Thank you

Re: Tachometer
 

This is likely an "and this failed too".

The tach is driven from the engine speed signal out of the PCM. It's a white wire at the cluster plug IIRC. It's a digital signal. You can check the signal with an oscilloscope but don't plug a meter or anything else into it.

The PCM should be reasonably protected in the engine bay and I'd expect other stuff to stop working if the PCM wiring got damaged.

The 2001 uses air core motors not steppers like the 2003-2007.
Usually the air core gauge motors don't fail but sometimes the electronics get flaky.

Re: Tachometer
 

Thank you very much!!