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Discussion Starter · #1 ·
It’s been many years since I’ve been on here as my 91T has been collecting dust in my garage…I’ve finally come into some time to get back into it but I need some help identifying some plugs on the engine harness. It’s a 91T chassis with a JDM 3rd gen 3sgte in it and I know some of the plugs don’t get used but I can’t remember which ones these are…also the 2 wires for my fuel pump resistor solenoid pulled out of the harness side and I don’t know which way they go back in…please help…
 

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It’s been many years since I’ve been on here as my 91T has been collecting dust in my garage…I’ve finally come into some time to get back into it but I need some help identifying some plugs on the engine harness. It’s a 91T chassis with a JDM 3rd gen 3sgte in it and I know some of the plugs don’t get used but I can’t remember which ones these are…also the 2 wires for my fuel pump resistor solenoid pulled out of the harness side and I don’t know which way they go back in…please help…
55 = Distributor
56 = Coil
DC = Igniter
29 = Not 100% sure.
E1 = Pin 1 is Blue w/White. Pin 2 is Blue w/Black. In the photos they are set up correctly, not that it really matters as it is a resistor so can be wired either way.
 

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Also need help identifying these 2 wires. Engine bay fuse box 1 is black with a white stripe and 1 is solid blue…I can’t even find them in the BGB…please help!
The Black w/White wire is for the AC magnetic clutch.
The Blue wire is for the Cooling Fan motor power.
 

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Thanks, I got it running this afternoon finally…but my tach is not working so I’ll be chasing wires for a bit longer
The Tach wire is black. In pin 5 of the plug called EA3. The one I circled. It takes a signal off the igniter.
So it goes, Pin 4 Igniter, Pin 5 EA3, runs through the body harness down the left side of the car to plug IE1 in the left kick panel. Then it heads off to the gauges. Make sure all those connections are good and the wires are good and it should work unless the gauge isn't happy.
Electrical wiring Cable Electronic engineering Auto part Electronic device
 

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Discussion Starter · #9 ·
The Tach wire is black. In pin 5 of the plug called EA3. The one I circled. It takes a signal off the igniter.
So it goes, Pin 4 Igniter, Pin 5 EA3, runs through the body harness down the left side of the car to plug IE1 in the left kick panel. Then it heads off to the gauges. Make sure all those connections are good and the wires are good and it should work unless the gauge isn't happy.
View attachment 81609
Thanks, you probably just saved me a ton of time👍😁
 

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Discussion Starter · #10 ·
I read a post a while back about someone that had swapped a 3rd gen 3sgte into a 91T and their tach didn’t work and they kept blowing their 7.5 amp gauge fuse in the drivers side kick panel, but the issue was resolved after they moved one of their wiring connections…but now I can’t find that post. Anybody remember that?
 

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Interesting. But you aren't blowing a fuse?
I assume you've done your checks of the wire? The black wire is sort of hiding in your photo but it appears correct in the fuse box plug. Toyota didn't really change the wiring in this plug apart from the air temp sensor and some AC idle up stuff depending on the model. The tacho stayed the same except for maybe the BEAMS 3SGE version which could still be in that location knowing Toyota.
 

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Discussion Starter · #12 ·
It is blowing the gauge fuse…I just pulled the whole engine harness off again so I can recheck everything but I did read a post that was very similar…I think the poster had to move one of the harness changes to another location(on the body harness maybe?) but I can’t remember and now I can’t find the post to review…
 

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Discussion Starter · #13 ·
Looking at the ecu connections and I can’t seem to match them up with any diagrams that I’ve found…does this look like it should? I have wires in places that are marked as empty 😳…Does someone have the correct pin out
 

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Ok. Lets figure this out.

I'm going to list as many wires as I can that go to the 7.5A GAUGE fuse and then we can check on your car if it is right vs the engine harness.

91 SW20 USDM wiring diagram
Page 72 Cooling Fan Warning light.
Page 55 Check Engine Light
Page 56 Potentially the ELS diode
Possibly more, I ran out of time to look.

Looking at the ecu connections and I can’t seem to match them up with any diagrams that I’ve found…does this look like it should? I have wires in places that are marked as empty 😳…Does someone have the correct pin out
Open up the ECU. The pinout is written on the board.
Also what is the pink wire coming out of the EA1 plug-labeled “CCo” in the diagnostic port?
CCo is Catalytic converter temp sensor.
 

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Discussion Starter · #16 ·
Many thanks! Here’s where I am now:

Opened ECU- no luck on finding anything useful.
What pages are you referring to for the 7.5 amp fuse connections?
Chased a ton of wires for ECU connections- see pics
Will not having the catalytic converter temp sensor connected effect drivability or performance?
 

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Font Audio equipment Office supplies Office equipment Electronic device


The text at each pin on he socket. RSC and RSO for idle control as an example.

1. Idle speedo control valve or ISCV.
2. IAT or Intake Air Temperature Sensor
3. Boost control solenoid or T-VSV. (Not TVIS)
The temp sensor is only there to note when your cat is getting too hot, I've cut mine off the GEN2 3SGE and no affects.
 

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Discussion Starter · #18 ·
Awesome thanks!…still trying to untangle the rats nest so I can be sure there are no shorts and everything is connected that needs to be. I’m also going to redo all of the common grounds because they’re all tangled throughout the harness and I’m getting sick of pulling pins to reroute wires…I’m going to have gray hair from this
 

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Discussion Starter · #19 ·
Ok, I’ve done the 26 pin plug now…the middle is what I have for wiring, the immediate outside is what’s printed on my ECU, and the far outside is what I’ve found that the abbreviations mean. There are a few that I’m not sure of though…I’m going to tackle the 16 pin next, this is tedious…
 

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Awesome thanks!…still trying to untangle the rats nest so I can be sure there are no shorts and everything is connected that needs to be. I’m also going to redo all of the common grounds because they’re all tangled throughout the harness and I’m getting sick of pulling pins to reroute wires…I’m going to have gray hair from this
Yeah the Toyota way of building these harnesses with the grounding wires all over the place is crazy. Nothing is simple.
 
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