I'm having a hard time identifying the part number for the ECU wiring harness. I did a hackjob while installing the IZZE secondary air pump simulator and would like to replace the harness now. Installed the simulator, but I'm still getting the secondary airpump cel. I think a wire has come undone, didn't do a good job with splicing... The harness I'm looking for is the one with the A and C connectors in the picture the one with the red arrow pointing to it. Do you guys know what this is called? I looked at parts diagrams but confused myself even more.

 

The following is not definitive:
From looking at the Electrical Troubleshooting Manual, it looks like that is Dashboard Wire Harness A.
I can find no parts reference to that harness, or the "B" harness either, only Wire Harness, Dashboard, which
appears to be the B harness. But the parts listings do show something called Wire Harness, Instrument which
is not listed in the electrical manual, but appears in the diagram to be in roughly the right place, and Harness A
does connect to the gauges, so my guess is that's what you want.

 

That sucks to hear. I'm not familiar with the air pump simulator, but perhaps you could give more info as to what went wrong on installation as replacing that harness is going to be more challenging than fixing whatever was messed up.

With that said-

Wiring harnesses aren't the same for all s2000's. I looked it up for a 2004 and I believe the part number is 32120-S2A-A02 or 32150-S2A-A62 (#4 or #5 on the diagram linked below). It is discontinued, as are most of the other wiring harnesses.

Check out this page for honda's diagram of harnesses. Search for your model year if its different than 2004.
https://www.hondapartsonline.net/v-2...--wire-harness