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Wed Jul 27, 2005 12:22 am

Hey damn i looked it up and totally forgot to reply. You probably already did it by now, but once i found the right place in the manual.. I remember what i did was go from the plug on the picture. There are 2 grounds one says GND other says SGND or something like that, you want the signal ground one not the general GND. If you need me to scan that page in the wiring section in the back of my manual i can.
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Sun Jul 31, 2005 1:50 am

Yeah, I tried signal ground, and couldn't get anywhere with that, I just got a ton of feedback when I tried that. Not sure what else to try.

Mon Dec 19, 2005 5:57 am

to add to this...

the 8" door sub speaker wiring can be found in the passenger side kick panel (at least in my 91 st185).

you'll should see two sets of wires, some thin and thick ones.

the sub speaker wires should be wrapped in a black tubing (like the cigarette lighter wiring) and the pair you are trying to find is the thick wires.

look for a solid blue with gray dots and a solid light green with gray dots.

Sat Jan 07, 2006 2:19 am

OK, I'm attempting the install as daveryan describes, but I'm having to hold the salesman's hand as I figure out the bits I need, and I need a little clarification myself.
First, is this unused plug the one that a standard Toyota stereo harness adapter will plug into (not the Metra 70-8112)?


Second, I came across a mention in another thread http://www.alltrac.net/phpBB2/viewtopic.php?t=677 that talks about plugging into 2 harnesses, but this is just confusing me. If I'm following the daveryan method and installing a separate, I don't need to touch these two plugs, correct? And are these the two plugs?

I don't suppose anyone has the metra # for the standard Toyota stereo harness?

Sun Jan 08, 2006 4:43 pm

Those are the two plugs and you do want to use them. Those are the wires going to the speakers after the amp, so use the non system 10 aftermarket harnesses with those two harnesses and you don't have to cut any wires!
I just finished doing this no more than two minutes ago and it works great, but you don't get the use of the subs in the doors. If you want those get a two channel amp to replace the stock one under the seat and wire straight to the subs from the amp (someone mentioned these sub wires being in the passenger side kick panel).

Sun Jan 08, 2006 8:28 pm

OK, I was digging around there just now, and I've figured out what most of the wires in those two plugs are for (although there are a few extras that I can't account for).

CalgaryGTS, You wouldn't happen to have the part number for the harness adapters would you? Is it one or two harnesses that I buy (there are two plugs - do I buy one harness for each plug?) Second, what did you do to get power, ground etc to the head unit? Or is that what the extra wires in those 2 harness plugs are for?

I do plan on getting a separate 2 channel amp to run the door subs, and now I know which wires I need to tie into.

Sun Jan 08, 2006 9:03 pm

It appears to be Metra 70-1761 - a very generic harness used on virtually every Toyota standard stereo system. Here is one seller.

This gives you everything but sub speaker wiring - it includes head constant power, head ACC power, ground, antenna power up and of course the mids & tweeters.
Here you can see it's actually two plugs:


And here's my $50 new old stock Blau head unit from eBay:

Last edited by daveryan on Mon Jul 17, 2006 1:35 pm, edited 2 times in total.

Sun Jan 08, 2006 9:25 pm

Thanks Dave - I actually just found this thread over at celicatech which has filled in all the gaps.

Tue Mar 21, 2006 12:42 pm

Update: 1990 System 10 harness now available here:

SIO Harness

Note however, the item is "out of stock" at the time of this post.

Tue Mar 11, 2008 1:13 pm

hey there!
the stock unit is ok, but cd has lost its capacitors (low sound), i might repair them, but the cdrom is bad at reading discs and i need some "aux in" for mp3 player, so i`m getting a new head unit..

i`m not sure, but do the TWO PLUGS differ between 90 and 93 versions? i got some 2piece harness that fits these 2 plugs (from ebay), just didnt try them with another head unit. as i understand the plugs are "after amp" connection. you said "get new amp and wire it straight to the subs. and where will the amplifier get signal from? do i have to do any additional wiring from the new head unit to the new amplifier?

Re: Simple Wiring Question for System 10

Fri Nov 26, 2010 9:06 pm

I installed a '92 3-in-1 factory unit in my 90 alltrac by using a donor amp harness out of a 92-93 GTS. It was different in length and design, so I just cut off the original end that goes into the radio and replaced it with the end from the 92-93 amp harness. ALL OF THE COLORS MATCHED!!! It was a piece of cake and I would do it all over again. From this point you should be able to use the Metra kit for the 92-93 Celicas with system 10. Good luck.

Re: Simple Wiring Question for System 10

Tue Apr 19, 2011 12:38 am

I have heard if you get an aftermarket head unit some of the speakers quit working. Is this true? If so, how do you resolve it. Do you have to upgrade the amp as well?

Re: Simple Wiring Question for System 10

Tue Apr 19, 2011 6:43 am

the amp is only for 8" subs in the doors. others play straight outta original head unit. if you replace it with an aftermarket one, of course u lose the subs. . no idea how to rewire it, but its been done. anyway the sound from aftermarket head unit with any shitty sound processing will give better sound than the original unit with the subs included. but i threw the aftermarket unit in garbage as i hate to take the panel off every time i step outta car, i live in criminal country, original is not considered a demanded item :D

Re: Simple Wiring Question for System 10

Tue Apr 19, 2011 1:43 pm

That is why I am installing an Alpine tape deck. Who would steal that. However it will control a hidden disc changer and ipod.

Re: Simple Wiring Question for System 10

Tue Apr 19, 2011 1:56 pm

Hey guys,

Wondering if anyone could give me some advice on getting the door cards off. I can't seem to even budge them with all the visible screws out. Don't really want to break something!
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