1G 91+ Power Transistor with 90 ecu

[Djsniperwolf]

I have been in the process of restoring a 90 GSX. The power transistor harness is missing the clip and is a bit broken.

On any type of pull, the connector loosens and the car shuts off. Zip tying does not seem to be working.

I have a 91+ transistor and connector that I would like to splice in, but I cannot find any solid information or diagrams. Everything I find pertains to swapping the ECU.

How does everything get connected, and do I need to splice into the wires of the ECU? Is there a diagram available?

I vaguely remember doing this some time ago on another car with the coil packs from a 91. I remember having to retain the tach connector from the 90 coil pack on the 91+, but I don't remember ever having to splice anything on the ECU side. Anyways, any help would be greatly appreciated.

 

[19Eclipse90]

Wire up the '91+ transistor exactly as would be found in a '91+ car with the exception of two pins on the '91+: 5 and 6. Both of these will be ignored. Pin 5 wire would be the source signal for the tachometer but since you are keeping the '90 coil pack, do nothing to the '90 coil pack wiring and it will be unnecessary to run a wire to the '91 PTU at pin 5. The tachometer signal will remain sourced from the '90 coil pack. Pin 6 is not necessary (and not available in '90 harness). The pin arrangement would change to:

90 PTU -> 91+ PTU
1 -> 8
2 -> 7
3 -> 3
5 -> 2
6 -> 1​

Where the '90 PTU harness has the following wire colors:

1 - yellow w/ green
2 - yellow
3 - black
5 - yellow w/ red
6 - yellow w/ black
​

This can all be done at the connector for the PTU.

 

[Djsniperwolf]

Wire up the '91+ transistor exactly as would be found in a '91+ car with the exception of two pins on the '91+: 5 and 6. Both of these will be ignored. Pin 5 wire will remain sourced from the '90 coil pack and will keep the tachometer working. Pin 6 is not necessary (and not available in '90 harness). The pin arrangement would change to:

90 PTU -> 91 PTU
1 -> 8
2 -> 7
3 -> 3
5 -> 2
6 -> 1​

Where the '90 PTU harness has the following wire colors:

1 - yellow w/ green
2 - yellow
3 - black
5 - yellow w/ red
6 - yellow w/ black
​

This can all be done at the connector for the PTU.

Ok that actually clears up a lot for me. I have included an image, is that the correct numerated order? When I replace the 90 transistor harness with the 91+ harness in the car and I splice the wires, do i just tape off wires 5 and 6 as they will not be connected to anything? Everything else makes perfect sense, but i just want to verify that I have a correct understanding of the 2 wires that will not be connected.

Thanks for the help.

You must be logged in to view this image or video.

 

[19Eclipse90]

The numbering on the '91+ PTU is backwards. On an original '91+ PTU, there is no pin 5. The only way that works with the orientation shown is numbering 8->1 from left to right.

Do note that the FSM uses the convention described here in detailing pin numbers for all connectors, not just ECU connectors: How to identify ECU pin numbers. That is, by looking at the reverse side of the connectors pictured and with the locking tabs on top, number from 1 on the left to the highest number on the right. This can also depend on which connector being investigated for intermediate connectors, but it generally holds for sensors, the ECU, coil, PTU, etc.

Either tape off or remove the number 6 pin / wire from the '91+ PTU connector.

 

[Djsniperwolf]

Perfect! That clarifies everything. I am in the process of running 4ga to the alternator, etc. But it seems that I have found another issue regarding some sludge in the reservoir. I'll save that for another thread. Thanks again.