1989SC 4agze swap into 1986 MR2, SC wont engage

[Mantle]

I've run into a problem with the SC swap in my car. The SC won't engage and here's what my mechanic has to say:

The problem is in the ECU sensing it's time to engage the SC. Everything works and has power but the ECU will not switch on the SC. I tried 3 different relays, a ton of wiring options and a different ECU which is the last chance fix. All with no luck.

You can manual lock the magnet and engage the SC by bypassing the switch/ECU but the ECU will not do it by itself. I'm stumped. There is a gremlin in there that will take a much smarter person than me to find. Maybe you check the forums to see if anyone else has had this problem after a swap.

The donor 4agze came from a complete 1989 SC car with damaged body, so I have all the parts necessary to do the swap. The subject car is a 1986 HT automatic. If you have any ideas of what the problem might be I would appreciate it. The only thing I can think of is the guy that originally started this project messed up the wiring job because of the differences between NA / SC harness.

[camshaft]

So I assume the cel works and no codes present ?

Looking at bgb

You said sc engages with power on the R #2 terminal to clutch?

Does it engage with power at sc relay pin 4

And you have power at pin 2 ?

If so then you need to connect something to relay pin 3 from ecu and see if ecu is grounding it.

If not then you have to verify all ecu powers and grounds

Then next would be to verify all inputs to the ECM are correct.
As if for some reason an input sensor is off the ecu is going to take the safe route. And shut down the boost.

Good luck

[Mantle]

Thanks Cam, I've passed the info on... I hope it helps.

[camshaft]

That or just install a msd rpm activated switch
Obviously computer is better