So I've been trying to get this done for quite some time. I think I'm still confused on a couple things, but right now my brain is fried. Can someone check this to make sure it's right? I can make changes as needed.

This is set up for my 1990 ECU. 1991+ will just need to swap #6 and #14. This will not be going in a DSM. This is a custom setup.

Really? No one has any input? Does this at least look right? I completely eliminated the ISC wiring and have consolidated quite a bit of wiring. I just would like some second opinions before I plug this into my ECU and see if it works

On the factory wiring the Black/White wire you show at the top goes to the ignition switch run position.
The Black/Yellow you have going into the MPI relay from the starter relay and the one you have from the ignition switch to pin 108 are the same. Unless your using a clutch safety switch you don't need the starter relay just run both from the ignition switch start position or a push to start switch.

You don't need both 63 and 66 connected at the ECU, it's already bridged on the ECU.

A 91+ power transistor will have a white wire to pin 109 for the ignition pulse detect using 90 parts that comes from the pin on the coil pack. This is when your tach signal would also connect.

The CAS only has one red wire not two.

Your missing the ECU grounds on pins 101 and 106 and if you not using the park/neutral input (pin 104) for NTLS/Stutterbox it should be grounded too.


That's what I see offhand.

Thanks for having a look.

Yes, there should only be one Red wire on the CAS. However, the ground coming from there is also connected at pins 101 and 106. It's not very clear in my drawing though.

Yes, the BW wire going to the MPI Relay, Coil and Power Transistor should also be connected to switched power at the ignition.

I didn't realize that 63 and 66 were bridged in the ECU. I just followed the stock wiring diagram. I don't see the harm in leaving it this way. Should I change it?

I think I will put a wire in pin 104 for later use in case I decide to go with NLTS. Do I need to ground it now, or is leaving it open the right way to run it?

My only BY wire is going from the MPI Relay to the starter relay. The wire in pin 109 is my tach signal. Labeled as "Ignition Pulse Detect" on the Pinout Diagram I have. Will I need to change this since it's a 90 ECU? I have a 90 Power Transistor laying around I can use. Do I need to run that with my 90 ECU or will this work? Or should I simply swap my 109 into 110?

My only wiring diagram is the crappy Chilton manual and an online Pinout Diagram. I rarely see info on the 1990 stuff, and I know there are a couple of differences in parts. I'll fix this diagram and post another for people to look at.

Thanks for helping out Steve.

There is no hard in running both 63 and 66.
Ground 104 for now.

BY goes to both the MPI relay and 108 (my typos before). It's the start signal from the ignition switch.