'90 Dash Harness Different From '89 Engine Harness

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Hotwheelsjr

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May 22, 2011
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Hi all -- I did some searching and have come up empty, so please forgive me if this is buried somewhere on the site. I just installed a '89 7MGTE/R154 into a '90 MKIII that originally had an auto and 7MGE. Previous owner did away with the auto and a 7MGE/W58 was in place and ran great until I toasted the head gasket (of course). I am going AEM EMS with the GTE and I expect the ECU connectors are fine. My dillema is plug B1 that connects to the dash harness. The '90 dash harness is a 15 pin gray connector and the '89 7MGTE engine harness is a 22 pin gray connector. Was '89 unique? I thought 86-87 was the same, 88 was unique, and 89-92 was all the same for the engine harness? I found that the pre-88 harness had a yellow 22 pin B1, but this '89 is a gray one! Can I cut the '89 22 pin one off and splice ont he 90 15 pin one per wire color? The '89 harness does have more wires "in use" -- will I be missing something critical if I splice the '90 connector in place of the 89 and leave the unused cut wires alone? HELP! My AEM EMS is supposed to be here Wednesday and I need to get this wiring complete so I can hopefully have it running this coming weekend.

THANKS!

-- Mike

Here is a pic of the two B1 connectors. The one on the left is my '89 7MGTE engine harness and the one on the right is the '90 7MGE plug I chopped off that will connect to the '90 dash harness.

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ForcedTorque

ForcedTorque

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I have a thread I started a couple of years ago that should help you alot. I'll go find it after posting, and edit with a link. What I learned, is that 89 is a beast all it's own! It had no air bag. 90 added the air bag, so it is different. Then, in 91-92, they have different connectors all together. The ECU plugs will all work, but the body plugs is where the problems come in. I wish the 89-92 MYTH would go away on wiring harnesses.

I used my thread to convert an 89 harness to fit my 92 body. I got a lot of good help in there thta may help yo uas well. You don't want to cut your plugs off. You want to de-pin those connectors, and use uncut wirng in the other connectors. Your air bag wires in the 90 will not have wires coming out of the 89 harness, so you will lose that. People will say that the car is old enough that it probably doesn't work anyway. I'll tell you the one in my 90 still worked from experience. I wish I still had that car.
 
ForcedTorque

ForcedTorque

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Here is the link to my thread. There are wiring diagrams on a couple of the pages. Some might not help you, but others might. 92TealSupra (Eathan), who helped me alot does not have a Supra anymore, so he's not around much anymore. But, if you PM him he will get it and help usually. Even with this thread and all of the help, I still have a few issues that I'm not willing to live with once the car ever gets on the road for good. I'm going to pitch it and buy a 91-92 harness.

http://www.supramania.com/forums/sh...1-90-Wiring-experts-Please!&highlight=harness
 
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Hotwheelsjr

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May 22, 2011
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Excellent! Thanks much! I'll go through it best I can and hit some of those members if need be. A lot of the stuff these plugs support I really don't care about -- I just want it to run. I will be running AEM EMS and can care less about the CEL, airbags, ECT (I have a R154), TEMS (don't have it), ABS (don't have it) or theft deterrent horns and such. I just need to make sure my ignition and fuel works along with the tach and gas gauge. The other gauges are useless as I have after market gauges covering them. I am working with an '89 engine/ecu harness and '90 chassis. I don't have a B2 connector on the engine harness, so I'm not too worried about it...from what I understand it is all for TEMS and ECT. The M1 and B3 connectors were the same between the harnesses...not sure if the wires are the same, but the connectors snapped right into place. The one connector I have different is the B1...and it has all the fuel and ignition stuff on it. This is where I need the help. I am not going through the trouble of pulling pins if I can avoid that -- I have a professional crimp tool that installs sealed crimps, so my plan is to cut off the '89 engine harness plug and splice on the '90 engine harness plug (to mate to the '90 chassis harness) I have pictured to the right in the previous picture I posted. I believe my C1 plug is already taken care of -- I'm using a '89 ignitor, so it plugged right up.

So, the age old question is are the wire colors the same besides the red or brown rings they added? Reading through your other thread, I'm 99% sure the answer is yes. Second question is, seeing the M1 and B3 plugs plugged right into each other, are there any wires I need to worry about from them that "should" be in the B1 plug? I have the pinout for the M1, but not the B3 connector.

Thanks again for your help!

-- Mike
 
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Hotwheelsjr

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May 22, 2011
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Anyone else have anything to add? I spliced on a 90 B1 connector in place of my '89 engine harness B1 connector color for color...I think there were 6 wires left over from the 89 plug and from what I understand they go to the B2 plug (don't have one) and are for TEMS and ECT. No big deal -- I don't need them. I plugged in a stock ECU today to see if I could get fuel pressure and I have no power to my fuel pump or fuel gauge. The fuel pump relay wire is yellow and properly spliced, but no dice. I know I can bypass the relay and jumper the FP (Walbro 255) with a fused toggle switch, but the gauge doesn't work. Any idea why they don't have power?

Thanks -- Mike
 
suprarx7nut

suprarx7nut

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Nov 10, 2006
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Honestly, I would go through the wiring manual (Buy one on ebay if you dont have one for your year car) and go through the circuit checks. They go pretty in depth. You may be able to chase down the problem faster that way.
 
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Hotwheelsjr

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May 22, 2011
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Ok -- so I'm a dumbass. I figured just turning the key on would turn the fuel pump on, NOT! Took a look in the manual and found the "procedure" to check the fuel pump and it works peachy. Thanks again folks...hope to have her running in the next day or two!
 
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Hotwheelsjr

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May 22, 2011
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IT RUNS! Finished up the exhaust and drive shaft tonight and fired her up. Started right up on a stock ECU. It's running full lean at idle, though. As RPMs climb it richens up, but as soon as I let off she goes full lean (AEM wideband is just displaying dashes). Took it for a couple of spins around the block and have boost set at only 5 psi...it richens up under light boost and drops right back to about 17:1 "cruising" at 30-40mph. I'll have to take a video of the AEM to see what it's really doing...too hard to watch it and the road at the same time...LOL. I tried playing with the base fuel pressure to no avail...stays lean at idle. My EGT peaked at 500* after driving for a short while. Any ideas how to richen it at idle and cruise without any piggy back (SAFC-II...I do have one, but it's not hooked up) or the AEM EMS installed? In the next week or so it will head for the dyno and the AEM EMS will go in and it will be tuned to about 20 psi, hopefully.

Second problem is pretty much nothing on my dash works -- gas gauge, dash lights, tach, etc... Any idea why? Also -- I have a Prosport oil press gauge with the sender installed on one of my oil cooler lines. I get 0 psi. Baffled by that too...there should be pressure in those cooler lines. The gauge/sender is brand new...I don't suspect the sender to be bad, but maybe?
 
suprarx7nut

suprarx7nut

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Lean at cruise and idle is normal and intentional by Toyota. Gas Mileage anyone? ;)

For your gauges, sounds like your M1 connector is not plugged in. That connector feeds your dash with info and without it not many of the gauges will work. Boost and voltage are the only two that don't go through that connector.

Now for oil pressure: By "cooler" lines, do you mean the stock system's cooler lines? Because it's not a full flow system so unless you have an aftermarket, full flow oil system you won't see much pressure in the cooler line. You'll need to relocate that sender.
 
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Hotwheelsjr

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May 22, 2011
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Ya...the stock cooler lines. Barely any pressure in thos lines is what I figured. Thanks!

I'll have to double check connectors but I am pretty sure the only connector I don't have connected is B2....

Thanks all!
 
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