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Courtesy of user ac4000 (Adarsh) from board.mr2faq.com

So, got yourself Metra part no. 70-8112 and the connections look wrong? Yep, you've got yourself a '91 premium system. This unit appeared on the earliest MKIIs (possibly some '92s, but I haven't heard of any) and, unfortunately, to install an aftermarket system, you can't just plug and play. (The connection/wire color chart is below for those of you who want to jump right in.) You have two options:

a) You can wire in a new head unit (HU) and keep the existing amp (easiest and, since the premium amp is decent, you'll get good sound--my aftermarket HU makes a bigger difference than I thought it would); or

b) you can rewire everything, bypassing the factory wiring.

Here are instructions for a (for b, you're on your own). Make sure you use a HU with preamp (RCA) outputs--DO NOT send high current output to the amp! I'll assume you know how to dismantle your dash and pull the old system, so this only describes the wiring:

1. Get a 14-pin harness. You can pick one up from any electrical supply store. If you can't find a 14, you can use a 12, just attach the RCA connectors to the car side and you'll free up five pins on the harness. I picked up Mar Vac's part no. 11-06012 (made by Propart) for $4.39 (it's called a "Round Multi Pin Locking Connector"); it's a 12-pin, so I just skipped the BEEP and MUTE wires because my HU doesn't use them.

2. Get a short run of standard RCA stereo cable (or pick up four male RCA jacks, if you prefer). This will cost a couple of bucks.

3. Cut off the factory harness, leaving a little bit of wire in case you want to use old system again someday (save the old part). NOTE: The factory side includes two green wires and two brown wires--tag them so you know which ones go to which pins before you cut the harness!

4. Your "chain of connections" will look like this (the HU harness is what plugs into the back of your HU):

[CAR WIRING]-----[splice]-----[14-pin harness M][14-pin harness F]-----[splice]-----[HU HARNESS]

5. Connect factory wires 1-14 to wires 1-14 on the 14-pin harness. This just makes things easier to keep track of.

6. Connect your HU harness wires to the 14-pin harness as follows (note also that the 14-pin harness pin numbers correspond to the factory wiring, and I've provided the factory wire colors, if you decide to just wire this stuff directly--remember L = blue, GR = gray, and P = pink, in Toyota BGB parlance):

14-pin harness pin number (factory wire color) --> HU wire
1 (P-L) --> Amp/Remote Turn-On
2 (G) --> ILL+/Dimmer (+)
3 (L-O) --> +B/Constant Power/Battery
4 (B) --> MUTE
7 (B-R*) --> ANT/Power Antenna
8 (W-G) --> ILL-/Dimmer (-)
9 (GR-R) --> ACC/Switched Power
10 (BR) --> GNDL/Ground (Primary)
12 (Y) --> BEEP

* The BGB shows this as G-B, but on my car it was not.

7. Connect the remaining 14-pin harness wires to your RCA connectors. Remember that the center RCA pin is positive, so connect all the center pin wires to the appropriate wires on the 14-pin harness. Connect all the negative wires together and splice them to GNDS (pin 11) (five wires will splice together for this part). Working with RCA wires is a bit delicate, so you may find it easier to buy RCA jacks. If you do that, you can run some extra wire to split GNDS into four wires (one per jack). Here are the speaker assignments:

5 (W) --> FL+/Front Left (+)/White Front RCA Connector Tip
6 (R) --> FR+/Front Right (+)/Red Front RCA Connector Tip
11 (G) --> GNDS/Speaker Ground/Speaker (-)/All RCA Negative
13 (BR) --> RL+/Rear Left (+)/White Rear RCA Connector Tip
14 (L) --> RR+/Rear Right (+)/Red Rear RCA Connector Tip

8. Tape up your HU's high-level output wires so they don't cause any problems (you won't be using them, of course).

9. Plug your HU harness into the HU, connect the RCA plugs, plug the 14-pin harness into the one you've added to your dash and you're ready to rock 'n' roll.

If you later decide to reinstall the factory unit, pretend the part you cut off earlier is the HU harness and wire as above. You may want to attach four RCA connectors to make things neat.

Installation Pictures

Dash area with 12-pin harness spliced onto the factory wiring:



Rear of the HU with 12-pin harness spliced onto the HU harness and HU harness plugged into the HU:



(Note, I used a 12-pin, rather than a 14-pin, and skipped the BEEP and MUTE connections, since my HU doesn't use them.)

Send me any questions or comments via email and I'll try to help you out if you're stuck. Enjoy!

Cheers,

Adarsh
 

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awesome, if you would like i can put up an install how-to similar to this on how me and my friend worked this out by going the by-passing route, it was a little time consuming, but a fairly simple install.
 

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posted by k2mr2
awesome, if you would like i can put up an install how-to similar to this on how me and my friend worked this out by going the by-passing route, it was a little time consuming, but a fairly simple install.
can you post yours too..






what are the color of the speakers? look at Gragon's post and im confuse of the color wire for the speakers...
 
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can some1 help please
i have power in my new HU but problem is when i connect the 4 negative wires on the HU to pin 11, HU wont work but if i just connect only 1 negative wire (say front left negative), then the HU work. power antenna is working as well (90 model MR2 Turbo)

question is where do i connect the speakers negative wireS? obviously i cant connect all of it to pin 11. help needed ASAP. just got the car and i got no toons to cruise wit
 

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i thought there is only one speaker ground wire? i only connected one... (i think) but my stereo would make a screeching noise when i turn the engine on... i still have to figure this out..
 

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I've got a Sony that I can't get the power to come on.

I used
1 (P-L) --> Amp/Remote Turn-On
2 (G) --> ILL+/Dimmer (+)
3 (L-O) --> +B/Constant Power/Battery
7 (B-R*) --> ANT/Power Antenna
9 (GR-R) --> ACC/Switched Power
10 (BR) --> GNDL/Ground (Primary)

I also combined the wires 1 and 7 to hook into the Sony ANT turn on.

I took out the stock HU Amp and Stock Sub Amp. Is this why my radio does not come on?
 

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I have removed the stock amp behind the passenger seat, side panel on the 92 turbo. I have also removed the sub woofer amp behind the drivers seat. When this is done, the following wires will not work.

3 (L-O) --> +B/Constant Power/Battery -- I ran a wire to the battery
9 (GR-R) --> ACC/Switched Power -- I wired to the cigarette plug
10 (BR) --> GNDL/Ground (Primary) -- I wired to car

I did not try 2 (G) --> ILL+/Dimmer (+)

So out of the orginal wires, I only used 1 (P-L) --> Amp/Remote Turn-On and 7 (B-R*) --> ANT/Power Antenna. I wired them together to get my antenna to work.
 

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posted by k2mr2
awesome, if you would like i can put up an install how-to similar to this on how me and my friend worked this out by going the by-passing route, it was a little time consuming, but a fairly simple install.

please please post this... im so utterly lost
 

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Keep in mind guys, that

10 (BR) --> GNDL/Ground (Primary)
is a SHEILD GROUND, as opposed to

11 (G) --> GNDS/Speaker Ground/Speaker (-)/All RCA Negative
which is a SIGNAL GROUND.

On better audio cable there are two wires surrounded by a sheild (or grounding sheild)
On the wire I use there is a red wire and a black wire and the full sheild.
The red wire would be the signal wire or center of the RCA jack. The black wire would be the signal ground and hook to the outside of the RCA jack. The sheild is NOT hooked to the RCA jack and is hooked (usually) only at one end although it might have to be hooked to the frame at both ends. Sometimes hooking both frame ground ends to the frame can cause "ground loops" and produce hum. You have to experiment.
 

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If you have '91 premium system, I still think the easiest way is just to bypass the amps. It's really not that diffucult a job.

I used

Constant power from the clock
ACC from the cigarette lighter
Ground from a bolt behind dash
Illumination to cigarette lighter illumination
and
(1) and (7) to power antenna

Then, I just ran new wire to the speakers and removed stock wiring. Pretty simple and just about anyone can do it.
 

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Okay, here's my contribution to the thread.

After reading this, I decided to tear the interior out and do this the right way. But to my dismay, I discovered that not only was the wiring to the stereo shot, so was the amp wiring and everything in between!

So I have some photos, and what I have learned, to submit for the group.

As mentioned above, the Toyota 91 Premium Sound wiring:

GR-R Switched power
BR Primary Ground
P-L Remote amp on
P-L +12v constant
B Mute
Y Beep

Now there will be a second bundle of wires inside the wiring harness sheath that will contain the speaker wires, and if I'm not mistaken the mute and beep wires along with a ground braid

W Front Left +
R Front Right +
L Rear Right +
BR Rear Left +
G Signal Ground (RCA -)



My vehicle harness was spliced INCORRECTLY with butt connectors, so I elected to make myself a custom wiring harness.



Since this was a last minute project, I had to make due with what I could find a Radio Shack. I DO NOT reccomend this, as they' don't have hardly anything like they used to. Do it right, and order a 14-pin connector.

Wiring the RCA (as mentioned above) is relatively easy. Remember that RCA plugs are center positive, and to tie all the negative wires together onto the signal ground pin.



In my case, the previous owner (who, if I find him, will earn himself a two month wheelchair ride) elected to butcher the crap out of the factory amplifier wiring harness, and wire the speaker-in wires to the speaker out wires. I went through and re-wired the harness by cutting out the bad sections, and soldering the wires back where they belong and heat-shrinking them for moisture resistance.



Keep in mind while you're doing this, that Toyota puts vehicles together intelligently. A wire will be the same code from start to finish, even if it junctions off (in the case of the door speaker harnesses) so if you have to re-attach wires to connectors the way I did, match them up and you'll be fine. I did mine the easy way and matched up color codes (and then cross-referenced the FSM wiring diagram book) and everything worked out as it should.

Now, for those of you that are having difficulty with your drivers-side door speakers not working at all, I discovered that the purple wire (door speaker wire) broke in the harness between the door and the chassis. The easy way to diagnose this is to take the door panel off, and the kick-plate on the driver's side. It will come off with the kick-panel along the bottom of the door sill in one peice. (or it should)

You will see a junction box, where wires plug into the chassis wiring harness. If you tug on the wiring harness inside the door, you will be able to feel what plugs belong to the door. The purple and pink wires on the smaller plug are your speaker wires. Continuity check them. One of my wires was bad. After tracking it back, all fixed.



I hope this helps some of you out there, or at least improves this thread, which was of great help to me!

Thanks all,
Will
 

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Very confusing...what happens if i just connect the wires from the HU harness and tie it with the factory wires? I have a feeling i'm commiting suicide :)
 

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2 Browns and 2 Greens

How do we determine which is for which
ON the browns there is one wire with silver lines that come in singles and another that has silver lines in doubles. THe green wires are identical. How do we know which is ground, rear left +, Ill+/ Dimmer, and GNDS for Speakers. I wouldnt want to get any of these wires wired inncorrectly. Can somone please help.
 

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To know which wire is which you can look at the pin numbers (if you haven't cut your factory harness).

1 (P-L) --> Amp/Remote Turn-On
2 (G) --> ILL+/Dimmer (+)
3 (L-O) --> +B/Constant Power/Battery
4 (B) --> MUTE
5 (W) --> FL+
6 (R) --> FR+
7 (B-R*) --> ANT/Power Antenna
8 (W-G) --> ILL-/Dimmer (-)
9 (GR-R) --> ACC/Switched Power
10 (BR) --> GNDL/Ground (Primary)
11 (G) --> GNDS
12 (Y) --> BEEP
13 (BR)--> RL+
14 (L)--> RR+
 
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