You should listen to me. No, seriously, listen to me.
Join Date: Oct 2008
Location: Santa Barbara
Motorcycle: Blue 2006 GSX-R1000
Re: K5/K6 ignition immobilizer
It's the other way around. The ignition switch sends a signal to the ECM.
The cleanest way is to replace the ignition switch and wiring harness with E33 parts. You're probably trying to avoid that. Have you considered flashing the ECM to the E24 spec? There are other ways but they're a bit cludgy.
If you want to maintain the E33 anti-theft feature, you need to run a line from the ignition switch's O lead to a 100 Ω resistor and a lead from that to ECM pin 21. You're going to have to buy a suitable JAE female contact. I'm not sure but you may be able to leave the second ignition switch connector in place. If not, disconnect it. Similarly, I don't think it matters that the Br/Y lead from ECM pin 44 runs to the cluster. But disconnect it if the light in the cluster acts up (and plug the empty hole with the leftover dummy plug from pin 21).
A simpler way (I think) is to run a 100 Ω resistor from ECM pin 17 to pin 21. But you lose the anti-theft feature by that.