Help with identifying wiring harness plug!!!

[hcorea]

Hi there I can't for the life of me find out what this plug is for or where it connects to. I've searched google and this place but I have no idea what this plug is called. It's a 91 automatic wiring harness I'm putting into my original NA 91 supra but swapping for a 7mgte. Does anyone know what it's for? I can't get any spark it turns over but wont ignite and I'm wondering if it has to do with this plug I'm holding in my hand. Any help would be appreciated thanks

 

[suprarx7nut]

That looks like the heater control plug so I doubt that would be your problem.

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[hvyman]

It's the m1 connector. Mostly for the gauges but can't remember everything that it goes too.

It doesn't plug into that other connector to the right in the picture that's not plugged into?

Are the grounds on the intake manifold clean and tight?

 

[IBoughtASupra]

You should have all the plugs in the computer plugged in. I believe there are three or four body plugs under the dash.

Does your check engine light come on when the ignition is on? Do the injector plugs have a 12V source on one of the pins?

 

[gatorm]

Or, did you do like me and put the bundle of brown wires onto the starter post. If you put the brown bundle or the white/black bundle on the starter, take them off and put them on a ground on the block.

 

[ForcedTorque]

You should plug that into the plug that is up and to the right of your hand in that picture. And, you need to be sure ALL of your graounds are hooked up. Here's the ones I can thin kof off the top of my tired head.

1. The bundle that gatorm mentions, that comes through the intake, and should bolt to a plenum bolt.
2. Back of the block, passenger side....goes to the firewall.
3. Tranny mount to the frame rail
4. From a bolt between tranny and block, driver side to the frame.

I'm sure I'm missing something. Maybe somebody else can help me.

Or, did you do like me and put the bundle of brown wires onto the starter post. If you put the brown bundle or the white/black bundle on the starter, take them off and put them on a ground on the block.

That bundle goes to one of the bolts between the intake manifold and intake plenum.

 

[hcorea]

Thanks for the replies I'll try to make sure everything is grounded and reply if I have any issues thanks!

 

[gatorm]

There is also a ground wire from the coil packs to the cylinder head and of course the main ground wire from battery (-) post to the drivers side of the block just behind the a/c compressor

 

[hcorea]

Alright I believe I've got the grounding issue fixed since I'm getting spark but now im getting no injector pulse; Any suggestions?

 

[hcorea]

The car is running thanks for your help but I have an issue-the gauge cluster does not work only the volt meter on it works. I assume it's because of these two plugs because the lights in the gauge work fine! They don't fit eachother though I'm completely baffled since they're the same year harness except the body plug is N/A and the wiring harness is the turbo one; What can I do?

 

[suprarx7nut]

I'll try to reply tonight. I should be able to track down all needed wires.

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[suprarx7nut]

Ok this was way too easy. I never read this at home and reading on my phone clearly had me skipping over some details. Your answer is in the second reply from hvyman. He's right, that's your M1 plug and it sends a bunch of signals to your gauge cluster. See the diagram below. See the little boxes with "M1" inside? That's your connector.

I bet the male end of the connector is stuffed in the ECU area hidden somewhere. The connector is the same for turbo and non-turbo. The volt meter still works because it doesn't use the M1 connector.

If you still have the N/A tach, you'll need to add a resistor to the tach for it to work correctly.

Let me know if that works!

 

[ForcedTorque]

Speedometer should be working also, as it is driver by the cable.

suprarx7nut....Whta color is the wire for the tach in that connector?

 

[suprarx7nut]

It's black and in terminal #4.

Speedometer also has a Pink cable coming from an electronic sensor inside the gauge cluster. This signal is used by the ECU as a parameter for Spark Advance and Idle Speed Control Valve and is in terminal #3 of the M1 connector. Pink wire going from M1 to ECU.

 

[hcorea]

Thanks for the help yea I changed switched the tach with a turbo tachometer so it should be fine but the issue is those two plugs won't fit. If that's really the M1 plug then clearly it is responsible for my gauge issues but it just won't connect to that female end it's too small. From looking at the two plugs they have the same colored wires so I'm pretty sure they are supposed to connect I just don't understand why they won't. Do i need to source a male plug and splice the wires onto it or what other alternatives do I have? There for sure are no other plugs down there everything else is connected to ECU and body plugs. I notice there are one or two plugs near the ignitor that aren't connected to anything could these also be contributing? I'll post pictures in a bit

 

[suprarx7nut]

Do you still have your old NA harness? You should have that same plug regardless of NA or turbo. Maybe somebody repinned those wires before you got the chassis? I'd check the old harness and see if it had the same small M1 plug. If your old harness had it then you MUST have the male end of the connector hiding somewhere in that ECU area. If the old harness does not have that plug then someone must have switched it out.

I was about to do that with mine...

 

[hcorea]

Shoot I sold my NA harness a year ago there's no way for me to check it. Can you look at your plug and compare it to my picture you should be able to tell the size difference. I don't know the first thing about wiring so I may be screwed for awhile until i can find the right plug to switch it with...

 

[suprarx7nut]

From left to right (top three): B3, B2, B1. The one below is the female M1 connector.

The M1 connector should be small and is routed above your head if your looking at the ECU area. Here are the wires attached to the cross bar right above the ECU.

If that connector you have looks like it has wires going back over top of the ECU then maybe the PO repinned those wires. The unplugged connector in your pic looks like the same as the B3 connector. The M1 connector is just as small as the one on your engine harness. Hope that helps.

 

[hcorea]

Thankfully I found my old NA harness and yep, the M1 connector fits. The problem is the connector on my engine harness it's from 89' so it won't fit into my 91' female connector. Now I gotta cut the NA male connector and repin the engine harness connector to it so they'll connect up. I don't know the first thing about doing this though is there some instruction manual that teaches you how to splice wires to connectors or something? Thanks for the help btw I appreciate it

 

[suprarx7nut]

Thankfully I found my old NA harness and yep, the M1 connector fits. The problem is the connector on my engine harness it's from 89' so it won't fit into my 91' female connector. Now I gotta cut the NA male connector and repin the engine harness connector to it so they'll connect up. I don't know the first thing about doing this though is there some instruction manual that teaches you how to splice wires to connectors or something? Thanks for the help btw I appreciate it

Glad I could help. Learning wiring stuff can be a bit tough at first, but if you google "Making wire splices" or "making wire crimps" you'll get some good scattered info. You'll need a crimper, a butt splice and a wire stripper. It's simple stuff, but it's easy to do a poor job on it.

It's good knowledge to have though, so you wont be wasting time if you learn to do it right.