Tach Probelm?

[92super4x4]

My tach reads 3k RPM as soon as the iginition is on, but the vehicle is not even started. As soon as the truck is started the tach migh move to 32k and move a little at acceleration, but it is way off. This is a factory tach that came with my truck. When the ignition is shut off the tach goes back to 0. I have seen some other posts with people having the same problems, but no answers so I thought I would see if anyone else knows what is going on or have had this same problem and were able to fix it. So far I have checked for loose wires and bad grounds and found nothing.

 

[lastmanup2nite]

I've run into this exact same problem. I also get a code for erratic tach from the ecu. Any input would be helpful.

As a new member, I have to confess I've found some very useful information here before I finally decided to join up. Please excuse my reluctance and thanks in advance, (and in the past), for your advise.