This article presents the procedure for the ignition system wiring changes when swapping a 1991-1994 ECU into a 1990 car with a 90 wiring harness, gauges, and coil.
This procedure corrects the tach signal so your tach works with a 91-94 ECU. This procedure was covered on the KeyDiver web site which I give full credit for presenting the original wiring schematics.
The procedure has been removed from the site and this article is provided to replace it. There is another procedure used for the ECU swap ignition wiring but that way is much longer and requires many more parts.
converting a 1990 to a 1991-1994 ECU system
For this process the only part needed is a power transistor from a 1991-1994 2.0 engine (N/T or Turbo).
The 1990 coil plug has 4 wires coming out of it where as the 1991-1994 plug only has 3. The color of the wires on the 90 coil plug are as follows from the back of the connector.
1 2
3 4
1=Yellow/Black
2=Yellow/Green
3=White
4=Black/White
These two pictures show the 1990 coil pack connector and the four wires used.
The 1991-1994 power transistor (#J722T) has 8 pins while the 1990 power transistor (#J122) only has 6. The wire colors for the 91-94 are as follows from the back side of the PT.
1 2 3 4 5 6 7 8
1=Yellow/Black
2=Yellow/Red
3=Black
4=White
5=No wire
6=Black/White
7=Yellow
8=Yellow/Green
On the left is the 91+ PT and on the right is the 90 PT.
These two pictures show the 91+ PT and its wires.
The 1990 wiring harness is almost identical in the engine ignition area as compared to the 1991-1994. The wires needed from the harness are originally go to the power transistor the colors are as follows.
1=Black
2=Yellow/Red
3=Yellow
4=Yellow/Green
5=Yellow/Black
The first wires that need to be connected are the thick gauged Black/White wires on the power transistor plug and the coil pack plug. The transistor's wire needs to be spliced into the coil plug's matching wire. That is the only wire on the coil pack plug that needs to be changed the rest are untouched.
Then the 1, 2, 3, 7, and 8 wires on the 1991-1994 power transistor have to be connected to the corresponding colored wires on the 1990 wiring harness.
The next wire that needs to changed is the 4th wire on the power transistor, this wire needs to be lengthened to reach inside of the car so it can connect to the ECU. The wire needs to replace the 109# pin out wire, the ignition pulse detect, the existing wire that was in the 109# spot is to be left unconnected. The 6# and 14# pin out wires on the ecu need to be swapped also. This is a link that shows the pin out location and #'s on the ECU.
1G ECU Pinouts
If you have any questions or comments feel free to PM me at any time. Please remember to rate my tech article.
This procedure corrects the tach signal so your tach works with a 91-94 ECU. This procedure was covered on the KeyDiver web site which I give full credit for presenting the original wiring schematics.
The procedure has been removed from the site and this article is provided to replace it. There is another procedure used for the ECU swap ignition wiring but that way is much longer and requires many more parts.
converting a 1990 to a 1991-1994 ECU system
For this process the only part needed is a power transistor from a 1991-1994 2.0 engine (N/T or Turbo).
The 1990 coil plug has 4 wires coming out of it where as the 1991-1994 plug only has 3. The color of the wires on the 90 coil plug are as follows from the back of the connector.
1 2
3 4
1=Yellow/Black
2=Yellow/Green
3=White
4=Black/White
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You must be logged in to view this image or video.
These two pictures show the 1990 coil pack connector and the four wires used.
The 1991-1994 power transistor (#J722T) has 8 pins while the 1990 power transistor (#J122) only has 6. The wire colors for the 91-94 are as follows from the back side of the PT.
1 2 3 4 5 6 7 8
1=Yellow/Black
2=Yellow/Red
3=Black
4=White
5=No wire
6=Black/White
7=Yellow
8=Yellow/Green
You must be logged in to view this image or video.
On the left is the 91+ PT and on the right is the 90 PT.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
These two pictures show the 91+ PT and its wires.
The 1990 wiring harness is almost identical in the engine ignition area as compared to the 1991-1994. The wires needed from the harness are originally go to the power transistor the colors are as follows.
1=Black
2=Yellow/Red
3=Yellow
4=Yellow/Green
5=Yellow/Black
The first wires that need to be connected are the thick gauged Black/White wires on the power transistor plug and the coil pack plug. The transistor's wire needs to be spliced into the coil plug's matching wire. That is the only wire on the coil pack plug that needs to be changed the rest are untouched.
Then the 1, 2, 3, 7, and 8 wires on the 1991-1994 power transistor have to be connected to the corresponding colored wires on the 1990 wiring harness.
The next wire that needs to changed is the 4th wire on the power transistor, this wire needs to be lengthened to reach inside of the car so it can connect to the ECU. The wire needs to replace the 109# pin out wire, the ignition pulse detect, the existing wire that was in the 109# spot is to be left unconnected. The 6# and 14# pin out wires on the ecu need to be swapped also. This is a link that shows the pin out location and #'s on the ECU.
1G ECU Pinouts
If you have any questions or comments feel free to PM me at any time. Please remember to rate my tech article.
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