I've looked through the threads and through my wiring several times but I need some direction. I have put a JDM S5 turbo swap into my '90 GXL. I jumped the gun and bought a package without the ECU and a cut harness. I went to my local Mazda dealership and got a wiring diagram. It was a tall order but I spliced the N/A harness to the TII harness. I ran into problems getting sensors, cables and what not.
I can get the car to start by pumping the throttle. After it warms up it will idle on its own. When driving, its pretty gutless. I did as much troubleshooting as a Haynes Manual shows. Compression is excellent. Checked all my sensors. Timing good.
I did find out now on this forum that I should have a turbo or FD fuel pump. But I found on the FSM how to check for codes. The weird thing is, the MIL has never lit up for me. I grounded the wire from the warning light cluster and the bulb lights up so the bulb is OK. I checked the voltages at the pins on the ECU. Pin 1E shows 12 V all the time with the key on, check connector grounded or not. The check connector is good because it will show 12 V at its pin when not grounded, and 0 V when grounded.
Any ideas out there. I think it may be a ground problem. I have to check out Aaron's grounding thread.

Also, what is the mystery single wire connector sensor beside the water thermosensor? Don't see it in my schematic.

 

What ECU are you using?

 

I've got an N374. I thought maybe it was possibly fried, so I bought a second one. Still the same.

 

That's a J-spec ECU. Japanese S5's didn't have a CEL, so that ECU won't drive your US car's CEL. You have to connect up an LED to the green 6-pin diagnostic plug in the engine bay just like you can do for S4's. Then the code checking procedure is just like any US S5.

 

Thank you for the info. I'll keep you posted when I check it this weekend.