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
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