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Discussion Starter · #1 · (Edited)
I'm going to apologize ahead of time for what may seem like a redundant thread, but @Master Jedi's fantastic post (Create your own jumper harness for adding a sub) wasn't dumbed-down enough for me. Thank you to @removedonut for taking the time to get me straightened out. Sometimes I need to work at the 3rd grader level, that's the intent of this post.

Note that to do this the right way, you really should purchase 2 wiring harnesses: Metra 71-1761 (Amazon.com: METRA 71-1761 - Radio Harness Into Factory Radio - OEM HARNESS TOYOTA 87-UP : Electronics) & Metra 70-1761 (Amazon.com). These two harnesses allow you to build your own pigtail so that you don't need to hack into factory wiring. I also recommend getting a set of RCA cables with wires on one end, something like this: (Amazon.com).

Important Point: The wiring harnesses ARE NOT plug-and-play. The advantage they provide is the ability to plug into the stock amp and wiring harness; however, they must be re-pinned. Yup, I blindly tried this and it's not pretty; you'll get a very loud ~60hz tone out of your sub - glad I didn't damage anything.

If you haven't re-pinned a harness connector before, there are YouTube videos on how to do various connector types (I couldn't quickly find this exact one). Just get yourself a jeweler's screwdriver kit, then one of the smaller standard screwdrivers will allow you to release the pins, they slide out, and then you can put them in a different slot. Be patient in learning this, it's not hard once you find out how the connector is constructed.

The second problem I had is that I couldn't decipher whether Master Jedi's picture was of the female or male connector, so my second attempt had everything 180 degrees off (it's the female btw). The remaining pictures should help ensure you don't have this problem.

First, this is a picture of the stock harness plugged into the stock amplifier. Ignore the 2-wire harness on the right, it's not necessary; we're only going to work with the 9 wires in the 10 slot connector (pin 7 is unused). The four wires on the left, (blue/white & yellow/green) are the "less-amplified" (0-2V as measured by @removedonut) signal wires which we're going to grab for the RCA's. The next one over on the bottom (dark green) is the remote turn-on wire, you're going to want to grab this one as well and run it with your RCA's to the amplifier. Lastly, the 4 larger gauge wires on the right of the are for the door speakers and are already amplified; for the pigtail we're going to construct, you're just going to pass these straight through so they are unchanged.

Hood Motor vehicle Automotive design Trunk Bumper


ok, so now that we know the goal - let's talk about how to practically make this work. Please note, the color of the wires in my pigtail are completely irrelevant - it's only relevant what they are passing from the amp to the factory harness and which ones we're going to tap into. You should focus on ensuring each pin passes through the same way to the amplifier regardless of wire color.

It's best explained using the male connector of the pigtail we're building. This is the one which will go into the factory amplifier. Remember, I had to flip everything 180 degrees once I found out my problem, so my white/grey wires are now on the left and the red/yellow/orange/black wires are on the right (again, the colors don't need to match what you do). The white/white-black wires on this pigtail correspond to the white/light-blue wires on the factory harness connector and we will use these to create the Right RCA. The grey/grey-black wires on this pigtail correspond to the green/yellow wires on the factory harness connector and we will use these to create the Left RCA. The blue wire on this pigtail corresponds to the green wire on the factory harness.

Wood Space Electric blue Plastic Cable


For illustration purposes, here is the female connector (upside down, sorry) which is soldered to ensure all those wires pass through exactly. This is the connector that the factory connector will plug into.

Hood Motor vehicle Automotive exterior Automotive lighting Wood


And the completed pigtail (before I taped it up, so you can see the wires).

Electrical wiring Cable Gas Electrical supply Technology


Lastly, I know some of you may want to see what this did as compared to the factory wiring diagram, so I marked this up.

Product Rectangle Slope Font Parallel


Please note, these are not true line-level outputs; however, they seem to be low enough to be tolerable even by an inexpensive amp such as the one built into the RockGhost. That said, my gain is set almost at zero, but to me this is preferred because high inputs, low gains are associated with higher sound quality.
 

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The wires are all high level. The car’s standard external amp and dash speakers are getting high level power signals from the head unit. Connecting RCAs directly to these will have a lot of voltage and require the gain on the aftermarket amp to be really low. If the aftermarket amp has high level inputs, I would use those or you may want to get a high to low converter.

Edit: I see in another post you are connecting a Rockville Rockghost. This unit has high level inputs. Wire those in instead of using the RCAs.
 

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Discussion Starter · #3 ·
The wires are all high level. The car’s standard external amp and dash speakers are getting high level power signals from the head unit. Connecting RCAs directly to these will have a lot of voltage and require the gain on the aftermarket amp to be really low. If the aftermarket amp has high level inputs, I would use those or you may want to get a high to low converter.

Edit: I see in another post you are connecting a Rockville Rockghost. This unit has high level inputs. Wire those in instead of using the RCAs.
I understand your point completely, and based on the diagram from Toyota, those are not line-level inputs into the amp. That said, I'd so much rather use a line level input into an amp if at all possible. I really thought by having the Premium that I had that option. :-(
 

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I understand your point completely, and based on the diagram from Toyota, those are not line-level inputs into the amp. That said, I'd so much rather use a line level input into an amp if at all possible. I really thought by having the Premium that I had that option. :-(
The voltage range on the input to the factory amp and the input to the dash speakers is 0-2V, which is within the input range that would generally be considered to be line level. The dash speakers are just run off this very weak signal.

For example, here’s the spec sheet for my amplifier. It accepts up to 8 volts through the line level inputs, which to be fair is high. Pretty much every amp should be able to accept up to 4 volts over RCA though.

Font Number Circle Document
 

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This is a great write-up, and I don't want to fully derail the thread, but I'm curious if there are reasons other than budget that people aren't opting to remove the factory headunit/amp setup? Does the factory radio have dependencies with other systems in the car?
 

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The voltage range on the input to the factory amp and the input to the dash speakers is 0-2V, which is within the input range that would generally be considered to be line level. The dash speakers are just run off this very weak signal.

For example, here’s the spec sheet for my amplifier. It accepts up to 8 volts through the line level inputs, which to be fair is high. Pretty much every amp should be able to accept up to 4 volts over RCA though.
What volume did you measure that at? I agree, it isn’t a lot. All I was suggesting is they could just use the high level inputs since the Rockghost has them. I am sure with the gain all the way down it should be ok and not clip/distort at high volumes etc. The input for low and high are not too far off based on the Rockghost manual. And with 2ohm load on those channels with a weak head unit, you are probably right on the voltage. I never measured it at max listening volume and I have the base which run the doors and tweeters in parallel (premium has mids and tweeters in parallel). I have the Rockghost installed on my base GR86 with high to low converter off the head unit. With my high to low converter pot knob all the way up, the gain control for the amp sub is a little past mid. If I had the premium, I would probably have just used the high level inputs. Unfortunately for me, I had to tap off the front of the car, and at that point it made sense to do a high to low converter.


My install:

 

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This is a great write-up, and I don't want to fully derail the thread, but I'm curious if there are reasons other than budget that people aren't opting to remove the factory headunit/amp setup? Does the factory radio have dependencies with other systems in the car?
I personally like keeping OEM radios as long as possible. They give me less problems and look better than aftermarket options. Plus, budget.
 

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This is a great write-up, and I don't want to fully derail the thread, but I'm curious if there are reasons other than budget that people aren't opting to remove the factory headunit/amp setup? Does the factory radio have dependencies with other systems in the car?
The factory head unit is more integrated and allows you to set other non-audio type things. Overall it is a nice for a factory unit. I wish the DSP/EQ was a little better. It is possible to use aftermarket head units. In Japan, I know at least one of the models, come with a blank insert for you to install your own.
 

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Discussion Starter · #9 ·
This is a great write-up, and I don't want to fully derail the thread, but I'm curious if there are reasons other than budget that people aren't opting to remove the factory headunit/amp setup? Does the factory radio have dependencies with other systems in the car?
Not derailing at all. My situation is that this is 90% a track car, but the factory sound couldn't even drown out the drone of my exhaust. I don't mind the integrated head unit with Apple Car Play. I only wanted to add just enough to make the sound more full, while reducing any modifications and weight additions. If this were my daily driver, I would consider doing more because the mids/highs still leave a lot to be desired; I don't know if it is the factory amplifier or the quality of speakers, but I don't think it's the head unit; regardless, it's really is a sad excuse for sound quality in today and the small sub helps out a lot. This small upgrade allows me to get to and from the track in relative comfort.
 

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This is a great write-up, and I don't want to fully derail the thread, but I'm curious if there are reasons other than budget that people aren't opting to remove the factory headunit/amp setup? Does the factory radio have dependencies with other systems in the car?
Nobody makes a dash kit for this car. I’ve done some preliminary testing though, and it should be possible to mount a floating mount radio with a single din body (like the Alpine F409) into the factory location and just hope the giant screen covers up the unusable buttons. Next time I have a grand laying around i’ll buy one and see, this is just a normal single DIN i test fit last night.

Vehicle Motor vehicle Gear shift Speedometer Steering part
 

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Around 20-ish, which is close to the max on the stock system before distortion starts happening.
That is good to know. For the base GR86 stock speakers, I think it was about the same volume before they choked. I replaced my front, door, and rear speakers with the most efficient non-paper speakers I could find, and they are at my max listening volume at about 22-23. I have cranked it to 26-28 and they didn’t distort, but wouldn’t run that high as I would be afraid of killing the head unit amp. The factory setup has fronts at 2ohm and rears at 6ohm for the base, but I replaced the rears with 4ohm 4” speakers and front with 6.5” and 4” coaxial. So far no issues with the Denso head unit in this config.

 

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Nobody makes a dash kit for this car. I’ve done some preliminary testing though, and it should be possible to mount a floating mount radio with a single din body (like the Alpine F409) into the factory location and just hope the giant screen covers up the unusable buttons. Next time I have a grand laying around i’ll buy one and see, this is just a normal single DIN i test fit last night.
Wow, yeah, there isn’t anything in the US that I know of either.

Here is a thread of Japan options. I wonder if anyone imports those borders/brackets?

 

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That is good to know. For the base GR86 stock speakers, I think it was about the same volume before they choked. I replaced my front, door, and rear speakers with the most efficient non-paper speakers I could find, and they are at my max listening volume at about 22-23. I have cranked it to 26-28 and they didn’t distort, but wouldn’t run that high as I would be afraid of killing the head unit amp. The factory setup has fronts at 2ohm and rears at 6ohm for the base, but I replaced the rears with 4ohm 4” speakers and front with 6.5” and 4” coaxial. So far no issues with the Denso head unit in this config.

Sorry for what might be a dumb question, but can you just install a small coaxial speaker in the dash to replace the dash tweeter?
Do you just put it in and use the connection that previously was connected to the tweeter?
Cuz that sounds like a really efficient upgrade and not too hard.
 

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Wow, yeah, there isn’t anything in the US that I know of either.

Here is a thread of Japan options. I wonder if anyone imports those borders/brackets?

Offtopic but none of the Japanese models come with a head unit. The head unit in the US is not available in Japan, instead you can use a Toyota/Subaru unit or any other 2 din unit. However, while a 2 din unit fits, Toyota was nice enough to make their own unit slightly higher so if you buy a 3rd party unit I believe you'll end up with something like a 10mm gap on top.

The unit Toyota sells in Japan is around $2000 for the 9" model (and this doesn't even have carplay/android auto), or ~$900 for the 7" model that has a godawful ugly plastic piece to cover up the empty space.

I got suckered into paying the 2 grand... didn't want to go with 3rd party stuff from the start and didn't want the ugly plastic cover up piece on the smaller unit either. As long as I have Bluetooth audio I'm fine but yeah... it was the only thing on my car I wasn't that happy to spend this much money on.

Fun tidit, the Japanese units should also be able to connect/integrate to ETC units (Japan's system for automated highway toll registration) and drive recorders.
 

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Sorry for what might be a dumb question, but can you just install a small coaxial speaker in the dash to replace the dash tweeter?
Do you just put it in and use the connection that previously was connected to the tweeter?
Cuz that sounds like a really efficient upgrade and not too hard.
Yes, see my base speaker upgrade how to thread I linked to in this thread. That is exactly what I did.
 
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