Tach falls to 0 and blows ecu fuse with VTC enabled

[Mag00n]

I could use some guidance chasing this electrical dilemma.87 crx si with k20z1, just got it running.

When I have vtc enabled, as soon as I hit vtec my tach drops to 0 and the 10a ecu fuse responsible for 12v constant blows.

If I use a 15a fuse the tach still drops to 0 but the fuse doesnt blow and tach starts working again as soon I go below 5200/vtec

It does not do any of this when the car is in the air on jack stands

If I disable the vtc everything works fine vtec hits and the tach goes up as it should.

My datalogs show the revs out to 6500 when I let off, so the ecu is seeing the signal.

Things I have checked:

-All engine bay grounds with multimeter.

-continuity of VTC wires from sensor plug to ecu plug

-visual inspection of interior and engine bay wires, checking for loose or frayed wires

[Mag00n]

The current at the cylinder head ground is .06 and at the transmission is .03

[Spunkster]

Try the ECU in a known working vehicle and if it works as it should, then you will need to resolve the wiring problem in your vehicle.