Tach issues

[02x72]

On my '90 the tach is having some issues that I cant seem to figure out. Sometimes it will work just fine, and others it will not work unless I am in the throttle. When it is acting up it does not seem to affect the transmission in any way. The sensor is known to be good, Ive cleaned the the grounds on the block as well as any other that I can find, but it still does it. Any idea where to look?

 

[icanfixall]

The tach senser has nothing to do with a C6 trans. Those trans are controlled by vacuum. Only the E4OD needs several electrical inputs to operate correctly.

 

[02x72]

I know that, the issue is not with the truck in my avatar, it is the second one in my signature which has the E4OD

 

[jaluhn83]

Sounds like an intermittent open somewhere. Could be wiring, could be the sensor, could be the tach.... Unfortunately not much you can do beyond cleaning the sensor face, and checking all the wiring and connectors. About the only thing I can tell you is to try swapping out the sensor / tach and see if anything helps. It's a PIA to t/s these, sorry.

Unless you have an oscilloscope, then maybe you could look at the sensor / tach input.