Tachometer problem, Jump at start and when revving engine

Hello all my name is Damiano
I have a 92’ 3000GT VR4 USDM
My tachometer jump at 2500-3000rpm at start, but then stay at 0, when i accelerate jump again, i checked continuity of wires (Pin n°5 white wire PTU big connector, Pin n°101 of ECU and Pin 53 54 of connector D-04 behind the cluster, the connector at left up frontal viewed), i have changed condensers of tachometer, but I still have the same problem. :disappointed_relieved:

I have tested 3 different cluster.

I thank in advance who will help me

Do you have the pulses coming out of the PTU?

I have not yet had the opportunity to measure them with the engine running, in any case to measure do you need a multimeter or do you need an oscilloscope?

Oscilloscope will give nice clear readings and show dropped pulses.

I will try to equip myself with an oscilloscope and take the measurement, I will keep you updated.

I solved the problem, the ptu despite making the coils work, did not send the signal to the tachometer, I replaced the ptu with another used one I found at home and the tachometer started working again.

Thanks for your suggestions