All of the sudden I noticed that my tachometer is reading about 500 rpm low at various engine speeds. My understanding is that the tachometer gets a signal from the ICM. Does this sudden change indicate that the ICM is about to fail? Thanks for the input.

 

Nah, it's probably the solder cluster starting to go.

 

Can you provide a little more information about this? Do you mean the solder joints on the back of the gauge cluster where wires plug in?

 

yes