turtlepeas

I've long since replaced my burned out factory radio screen and have been using a couple of different FM bluetooth receivers which works fine. I stumbled across an android head unit that I think I like and am researching as much as I can to achieve as painless an install as possible. The best tutorials and articles I've seen are pretty straight forward.
Any aftermarket radio will come with it's own wiring harness that needs to be married to your specific models aftermarket wiring harness. My question is where can find a correct/reliable aftermarket head unit harness for my 98 es? Googling brings up results, but I've seen comments where people say to stay away from the Metra brand.
Also, I've read about the stock amplifier being an issue when replacing your radio; it needing to be bypassed or some such? If I'm looking to only replace the head unit would this not be an issue for me?

LeX2K

I've used Metra adapters they are okay certainly not high quality but they work. Not sure if there is a specific adapter that will utilize the ES amplifier? If you have the Pioneer amp here's the wiring specifics it can be interfaced to any head unit with line out.
https://www.clublexus.com/forums/es-...and-specs.html

IMO the Pioneer is a good amp a fair bit better than the built in amps of most head units.

BMeek

To utilize or integrate with the factory amp, buy the Metra 70-8112 "amp integration" harness. This assumes your aftermarket head unit has 4 RCA line outputs and you tape off the high-level speaker leads from your head unit. The factory amp will then take this presumably full range 4-channel signal and feed it to the 4 door speakers (6 if you count the front tweeter components) and the factory subwoofer.

This will work all right, but the factory amp is really designed only for the factory head unit. With an aftermarket head unit you will almost certainly hear background ground loop noise and a variable alternator whine (faint at times and louder at others). Also, you will likely hear a rather loud "pop" whenever the factory amp is powered on or off. I put up with these noises for quite a few months before finally deciding to bypass the factory amp.

The good news is that I discovered you can pretty easily make a clean reversible factory amp bypass from already having an aftermarket HU integrated to the factory amp using the Metra 70-8112. To do this and power your factory (4ohm) door speakers from your Head Unit's internal amp, or integrate an aftermarket external amp, buy ANOTHER Metra 70-8112 harness (connects to the amp-end of the wire bundle between HU and amp), and a Metra 70-1761 harness (plugs into factory speaker wiring and reroutes power & ground back to HU).


This shows the 3 wire bundles previously plugged into the factory pioneer amp (shown in its "bypassed" state behind on right) now connected to Metra 8112 and 1761 harnesses.



Incoming 12v power (12v accessory, 12v constant & ground) flowed through the factory amp to the Head Unit. Connecting the red, yellow and black wires of the '8112 and '1761 harnesses as shown will reroute power back to the Head Unit while bypassing the factory amp.

This factory amp bypass, as described, abandons the (2 ohm) factory subwoofer that's dependent on an external amp. My aftermarket HU, an ATOTO A6 Pro, has a decent internal amp that's said to deliver 29w RMS to all 4 door speakers. Connecting it directly to the factory pioneer door speakers (with the component tweeters in the front doors) clearly sounded much cleaner and better than the factory amp had (even when abandoning the factory subwoofer in the bypass). Your mileage may vary, etc. The good news is that you can now simply unplug your new harnesses behind the dash and reconnect to the factory amp for comparisons.


I later added an old Infinity BassLink powered/active subwoofer in the trunk, and removed the factory subwoofer from under the rear window (to let the thump out of the trunk). I also finally replaced all the factory door speakers with some well-regarded but lower-end JBLs, but this last "upgrade" made less difference than the amp bypass and the powered subwoofer had... those old factory made-in-japan Pioneer woofers in the doors are pretty hefty.

Some may suggest sticking with the factory amp by using multiple filters to remove the noise & pops, but the quarter-century-old amp and subwoofer aren't worth it. Put the relatively high cost of the filters toward a more powerful head unit to drive your door speakers, or to buy a powered subwoofer and/or an external amp.

By the way, I believe the gripes about Metra you saw complained that the 70-8112 harness lacks an orange wire for the headlight/illumination switch. Metra says it's not supported by the factory plug. I always drive with my headlights on day or night, so I didn't worry about finding a connection to the orange wire going into my aftermarket head unit. If there is an illumination wire that ran into the factory head unit via the 15-pin plug that connects to the Metra 70-8112, it joins the wire bundle along the way (at least it doesn't originate at the factory amp).

Finally, I credit @teamgoon in this ClubLexus thread from 17 years ago for pointing out that one should use the AAMP/Best harness #BHA1761 (Metra 70-1761 equiv) to cleanly connect into the factory speaker wiring originally connected to the factory amp (and also @NYC ES3 for starting that thread and the nifty amp wiring pic). Because my "amp integrated" HU lost power when I unplugged from the amp, and I had an extra 70-8112 harness on hand, I discovered how to also use it behind the dash to restore power to the HU and complete the amp bypass in an easily-reversible way!

FWIW, I had started to prep for writing this up for the Lexus Audio, Video, Security & Electronics forum and have been meaning to write the post for a while, but since a fellow 1998 ES300 owner was starting down the aftermarket head unit path and asking, I thought I would share it here first.

turtlepeas

BMeek, thanks so much for that write up and the time you put into it. And thanks for the info on the Android Head Units forum. I'll start a new thread to document it all once I get started.

BMeek

FYI, I posted an expanded version of this "clean factory amp bypass" method to the "Lexus Audio, Video, Security & Electronics" forum. I'm hopeful that people will find it more easily there, hopefully before following other instructions to cut & splice factory speaker wiring. Probably best to follow up to that forum.LeHHxus Audio, Video, Security & Electronics

Paul33570

I just installed a JVC unit I had in my Miata. I added ground loop insulators and the hum is gone. I used the factory amp, which I was impressed that it was still working after 22 years. Now thinking of adding one of those 10" Android units. The prices are so reasonable it's hard to believe. The JVC has no "extra" sound. The ground loop idolaters really work! I am not an audio guy lol!

User902748

I bought this
https://axxessinterfaces.com/product/TYTO-01
(The TYTO-01 interface is designed to allow the user to replace the factory radio with an aftermarket radio in select 2001-up Toyota / Lexus vehicles and retain the use of the factory amplified sound system.)
[https://www.ebay.com/itm/401124428315]

You can follow along the YouTube video I found [ ]

turtlepeas

A quick question. Since were connecting the color coded speaker wires of the Metra 70-1761 directly to the head unit harness, does this mean that it isn't necessary to connect the four RCA plugs of the original '8112 into the head unit itself?

BMeek

Correct. I unplugged mine from the head unit when I bypassed the factory amp (although it wasn't strictly necessary). Certainly no need to plug them in if you're installing a new head unit while doing an amp bypass.