ST185 IG1 and IG2 connectors (big grey and big white one)

[l0ch0w]

Its always been easy to track down the pinout locations of the ECU, but also on the engine harness are two larger but equally important connectors that go to the body harness...

It was important for me to know the purpose of each of these connectors because I am attempting to streamline my entire wiring harness, and make it "better" than OEM. I also am running a fully standalone engine management system, and it was important that I figure out what some of these connections were for so that I could retain complete stock functionality. Two of the pins are unknown... I searched through the whole of the wiring diagram and I could not find any mention of IG2 pin3 or pin17... I know the white-red wire goes to the check connector, and I believe the same for the white-blue wire... so they arent that important, but ill just make sure to reconnect them back in the same way I found them. CKC means check connector, and some of them I dont know what they mean, but I can tell you where they go and speculate on what their purpose is, really the most confusing seems to be the white-blue series of wires that go to the cruise, coil, CKC, and airbags.

Anyways, here are the pin numbers for the two connectors as described in the BGB (you are looking at the ones labeled IG1 and IG2). Note that the numbers reflect as if you are looking into the open end of the female connector.



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Below are the descriptions of most every pin. I had to spend quite a bit of time tracking all of these buggers down in the wiring diagrams, but here it is nice and compiled for you.

IG1:
PIN------Description----------Wire color

1-----------NOT USED------------
2------IDL (TPS switch)------Pink
3------Speed sensor---------Blue
4------A/C Switch----------- Black-White
5-----------NOT USED------------
6------VR3 (Cruise)----------Grey-Black
7------VR1 (Cruise)----------Grey
8------MC (Cruise)-----------Red-Green
9-----------NOT USED------------
10----------NOT USED------------
11-----Ground---------------Brown
12-----Oil Light (Gauge)-----Yellow-Black
13-----Water Temp (Gauge)-Yellow-Green
14-----Tach (Gauge)--------Black
15-----Turbo Pres (Gauge)--Red-White
16-----L (Cruise)----------- Red-Yellow
17-----VR2 (Cruise)---------Grey-Red
18-----MO (Cruise)----------Pink-Black

IG2:
PIN------Description----------Wire color

1-----------NOT USED------------
2-----------NOT USED------------
3------TC CKC---------------White-Blue
4------Backup light sw. in----Red-Blue
5------Fuel Cut--------------Green
6------TC CKC---------------White-Blue
7------+12V Battery----------Pink
8-----------NOT USED------------
9-----------NOT USED------------
10----------NOT USED------------
11----------NOT USED------------
12-----Airbag CKC------------Brown
13-----Backup light sw. out---Red-Black
14-----Ground (Gauge)--------Brown
15-----IG from alternator------Black-Red
16-----Battery light-----------Yellow
17-----Unknown CKC----------White-Red
18-----+B Switched power----Black-Yellow
19-----Fuel Pump CKC--------Blue-Black
20-----Starter switch---------Black

I can get a more accurate description of two unknown CKC wires later, i just dont really feel like ohming out my check connector at the moment...

[BoostedBlueToyotas]

I have a spare 90 engine harness in the basement. I will go down and check if I can figure out where those wires (what other connector they end up at) go . Hopefully I can remember to take a look.

[sMARTINside]

Here is a reference that I have made while swapping my engine:


IG2-3 is the TC pin, in the diagnosis box: IG2-3 is connected to IG2-6 so they are the same
IG2-17 is the TS pin, in the diagnosis box

They both are related to the ABS system. When you connect TC with E1 (ground) it will flash the ABS light to tell you which malfunction code was recorded by the ABS ECU, just like checking the engine malfunction codes. When you connect TS with E1 (with TC and E1 still connected) it will give you access to more codes. This all has to be done with the WA/WB jumper removed.

So TC and TS, in the diagnosis box are going to the ABS ECU, passing through IG2 connector.

[l0ch0w]

Here is a reference that I have made while swapping my engine:


IG2-3 is the TC pin, in the diagnosis box: IG2-3 is connected to IG2-6 so they are the same
IG2-17 is the TS pin, in the diagnosis box

They both are related to the ABS system. When you connect TC with E1 (ground) it will flash the ABS light to tell you which malfunction code was recorded by the ABS ECU, just like checking the engine malfunction codes. When you connect TS with E1 (with TC and E1 still connected) it will give you access to more codes. This all has to be done with the WA/WB jumper removed.

So TC and TS, in the diagnosis box are going to the ABS ECU, passing through IG2 connector.

Should have asked u first huh

I found the circuit in the BGB wiring, and i must have skipped over it... Turns out that the wiring diagram says it should be going through IG2 pin 2 instead of pin 3.... But whatever...

I think the TC circuit is the general check circuit, since it is also used for checking the airbags, and cruise control...

[sMARTINside]

I found out that sometimes, the BGBs aren't always right. My Celica's Chilton book isn't accurate at 100%. Some pins are mixed up, in the wiring diagrams. I checked about 1000 times over them, misunderstanding and came to the conclusion that the book was wrong, comparing with the real wiring, in the car.

[l0ch0w]

^ I noticed you didnt follow BGB convention for terminal numbering.

[sMARTINside]

Ohhhh, maybe! What is different, in the BGB? The way that i wrote it follows the numbering on the connector though.

[l0ch0w]

Oh... nvm you did it right, I screwed up and wrote green for when it should have said grey for a bunch of the wires and i got confused... I used short hand to take notes and I read gr as green instead of grey. Next time ill write gy for grey in short hand...

Anyways the errors have been corrected above in my original post...

[sMARTINside]

Good! Yeah, gr, can be for both! That is confusing!

[l0ch0w]

Why does the A/C amplifier have a Tach signal going to it???

[sMARTINside]

Maybe the AC amplifier needs to know at what rpm the engine is reving. Is there a pin, in the pinout that pointed this out?

[l0ch0w]

I discovered this while tearing into my harness... Apparently, the Tach RPM signal splits in the harness and feeds the A/C amplifier plug (small white one off the harness but still inside the firewall)

Did some research and found out that in order for A/C to come on, a tach signal must be present to verify that the engine is running...

Now comes the task of figuring out whether or not I have to modify my A/C amp so that itll be compatible with my standalone's 12v tach signal, instead of the OEM 20v Signal...

[sMARTINside]

Ok, thanks for the information, I just can't help you on that, since I ripped my A/C out of the car

[tubasteve]

I discovered this while tearing into my harness... Apparently, the Tach RPM signal splits in the harness and feeds the A/C amplifier plug (small white one off the harness but still inside the firewall)

Did some research and found out that in order for A/C to come on, a tach signal must be present to verify that the engine is running...

Now comes the task of figuring out whether or not I have to modify my A/C amp so that itll be compatible with my standalone's 12v tach signal, instead of the OEM 20v Signal...

I believe the a/c amp needs engine rpm signal cause it checks compressor rpm to make sure the pump isn't slipping.

[l0ch0w]

Think ill need an external tach adapter then huh...