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Discussion Starter · #1 ·
Hello all and thanks for allowing me to join the forum. I have an issue with my MK3 Supra in that I have a few connectors that seen to have no home. The car has been working okay until I needed to change the cylinder head gasket. Did a strip clean etc. I have 2 connectors that don’t seem to go anywhere. The car has been messed about with but the engine was running although I think the engine harness is not original. I have attached 2 bad photos in the hope that somebody can help. I am now having issues getting the engine to run. It will start and run for a few seconds and cuts out. It’s a 3.0 turbo. Any help appreciated
 

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Hello all and thanks for allowing me to join the forum. I have an issue with my MK3 Supra in that I have a few connectors that seen to have no home. The car has been working okay until I needed to change the cylinder head gasket. Did a strip clean etc. I have 2 connectors that don’t seem to go anywhere. The car has been messed about with but the engine was running although I think the engine harness is not original. I have attached 2 bad photos in the hope that somebody can help. I am now having issues getting the engine to run. It will start and run for a few seconds and cuts out. It’s a 3.0 turbo. Any help appreciated
What transmission do you have? The first pic (on left, more square than rectangle) looks like the ABS connector for the R154. No sure on the other one but may also be a transmission connector - reverse light maybe?
 

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Discussion Starter · #3 ·
What transmission do you have? The first pic (on left, more square than rectangle) looks like the ABS connector for the R154. No sure on the other one but may also be a transmission connector - reverse light maybe?
Hello thanks for your reply. The car is a manual but I have a suspicion that it may have an auto harness. I will have a look for R154. Thanks
 

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My 88 factory turbo manual also had two connectors I never found a home for. Not even when I built a new harness for the standalone I found where they go.

I also thought the harness in it was from an auto.

Everything seems to work too so...
 

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On an 87 Turbo with the R154, there are 2 sets of wires with plugs similar to this that head back over the transmission. They clip onto the bell housing front on the drivers side. One is for the backup light the other is for the ABS. You might be able to run it down by recording the wire colors / stripes and referring to the Toyota Supra wiring diagram. Here is a link to the online manual.
 

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Do your backup lights work? How about does the car start with the clutch out? Could be related on that front as well if its a manual swap car.
 

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Discussion Starter · #8 ·
Oh thank you for your responses I think I might give you an update on the problem I was having. It seems that the connectors go nowhere and at some point in time in the past the harness was replaced swapped from an automatic car. The symptoms I was experiencing was due to vacuum hose is not being collected the car now runs.
 

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@3p141592654 The ISCV connector is this one, much larger and in a different area of the engine bay. The two connectors OP mentions reach around the same area the two round sealed transmission plugs do.

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If you ever find where these went, I'd love to know. I never found out in my car nor found anyone who had the same issue - you're the only other person that I know of!

I wonder if Toyota at some point only had one loom for both MT and AT vehicles and simply left the unused connectors in MT vehicles unplugged. Mine's a factory MT turbo and it has those extra two connectors.
 
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