How to Connect an External Amplifier to an Android Headunit
Your front pre-outs are the white and red RCAs on Harness A, pins A4 and A6, and your rear pre-outs are the white and red RCAs on Harness C, pins C3 and C4. The amplifier turn-on lead is the blue wire on A1. Harnesses A and C ship with the unit, and you only connect them if you're running an amplifier.
9" MK4 Multimedia Headunit for Toyota LandCruiser 70 Series (2009-2026)
View product: 9" MK4 Multimedia Headunit for Toyota LandCruiser 70 Series (2009-2026)What this gives you
You get four channels of clean line level out of the headunit, so an amplifier drives the doors instead of the internal output. On a 70 Series you either lose the music at 100km/h on corrugations or you can still hold a conversation with it on.
The same harnesses also carry a separate subwoofer output and a 5.1 centre channel, so the amplifier isn't the ceiling of what you can feed off the unit.
Before you start
- Harness A, the front audio pre-out and AUX harness, and Harness C, the rear audio pre-out and centre channel harness. Both come with your headunit.
- Four RCA leads long enough to reach your amplifier, and a thin wire for the turn-on lead.
- Your amplifier already mounted, with its power and earth run. The headunit end is the small half of this job.
- The battery disconnected before you pull the fascia.
Step by step
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Work out how many channels you actually need
If you're doing front only, that's two RCAs off Harness A. Front and rear is four, so you add Harness C. A subwoofer is a separate output again on A16, and it doesn't use any of these four.
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Connect the front pre-outs
On Harness A, A4 is the front left pre-out and carries a white RCA plug. A6 is the front right and carries a red plug. Run those two to the front input pair on your amplifier.
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Connect the rear pre-outs
On Harness C, C3 is the rear left pre-out with a white plug and C4 is the rear right with a red plug. Run those to the rear input pair. If your amplifier is only doing the front, skip this harness entirely.
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Run the turn-on lead
A1 on Harness A is the external amplifier control, and the wire is blue. Run it to the remote or turn-on terminal on your amplifier. Without it, the amplifier either never wakes up or stays on and flattens your battery overnight.
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Leave the speaker wires alone unless the amplifier is doing that speaker
The 16-pin main plug still carries the four factory speaker pairs. If your amplifier is driving a speaker, don't also wire it to the headunit output.
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Set the gains with the headunit volume high, not low
Bring the headunit up to about three quarters of full volume on a track you know, then raise the amplifier gain until just before it distorts. Set the gain against a quiet source and you'll clip every time you turn it up.
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Check balance and fader before you blame the wiring
If you're missing one side or one end after the install, check balance and fader on the headunit first. That's a faster check than pulling your dash apart.
If it does not work
- If your amplifier never powers up, check the blue wire on A1 is on the amplifier remote terminal, not on a permanent supply.
- If you get sound from one side only, check balance on the headunit, then check the white and red RCAs aren't swapped or half seated.
- If you hear a whine that rises with engine speed, that's an earth path problem, not the pre-outs. Take the amplifier earth to a bare chassis point rather than a factory bolt with paint under it.
- If you get no sound at all from the amplifier, confirm the headunit still plays through its own speakers. That tells you which one is at fault.
Worth knowing
Harness A also carries an AUX audio input on A5 and A3, white and red, so you can run a second source in without touching the amplifier wiring.
