tach signal?

[1fast97gsx]

Is the only place that the ecu sees the tach signal from the power transistor? My tach is sticking and jumping around at anything part throttle over 3000 rpm, but it's not the needle physically getting caught since its very easy to manually turn it and move it around. I'm wondering if replacing the power transistor would take care of this or what else it could be? It does it on both of my ecus and 2 sets of coilpacks as well.

 

[steve]

The Tach uses the signal off the PTM. The ECU has several inputs that could provide RPM information, it used the CAS and Crank angle sensors for's it's reference and checks the PTM output for making sure the coil is firing.

Steve