I have a 98 civic with a 00 engine harness and ecu, the ecu is no longer getting constant power, the fuse is though so I think the wire broke somewhere, which wire is constant power?

 

obd2b ECU plug
you're looking for B21 and the 7.5a underhood fuse.

 

The '00 engine harness doesn't work in a '98 chassis directly... lots of wiring modifications are needed. You should get a '96-98 engine harness instead.

 

Thank you both for replying, the fuse is good, I'm assuming the wire broke somewhere so I'll run a new one. I noticed what you're saying JR when I had to wire plug a myself, the engine is also from a 2000, I think thats why the last owner just threw an obd2b in and called it good