Hondata

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

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

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.