A long time ago I used this Metra 70-8112 (crutchfield link) (amazon link) harness on my 96 Avalon (6-speaker) It adapts the RCA outputs from your head unit to use the factory amplifier. This is contradictory to your request to bypass the amp, but I figured I would mention if it you were interested in a plug-and-play that would clean up wiring.

I dug into the factory amplifier in this thread, and it is basically onpar, if not slightly better than most aftermarket HUs. it puts out the same RMS power, and its larger chassis means it probably outputs that RMS longer before thermally throttling.

Otherwise I think you are stuck in the route of splicing down at the amplifier plug as shown in one of your pictures, and extending the wiring up to the Pioneer unit. I'm pretty confident no aftermarket harness exists for these plugs. It gets a little ugly next because the factory amplifier provides power the stereo location. (power enters the amplifier though the blue plug and leaves to the radio in the green plug) So you would have to either 1) cut the speaker wires out of the plug, or 2) run new power wires (batt, acc, dimmer) to your radio, bypassing the need for the OEM amplifier to provide the power. Then you could just leave the the blue and green plugs detached... but you still need to splice onto the green plug for speaker wires though.

 

A long time ago I used this Metra 70-8112 (crutchfield link) (amazon link) harness on my 96 Avalon (6-speaker) It adapts the RCA outputs from your head unit to use the factory amplifier. This is contradictory to your request to bypass the amp, but I figured I would mention if it you were interested in a plug-and-play that would clean up wiring.

I dug into the factory amplifier in this thread, and it is basically onpar, if not slightly better than most aftermarket HUs. it puts out the same RMS power, and its larger chassis means it probably outputs that RMS longer before thermally throttling.

Otherwise I think you are stuck in the route of splicing down at the amplifier plug as shown in one of your pictures, and extending the wiring up to the Pioneer unit. I'm pretty confident no aftermarket harness exists for these plugs. It gets a little ugly next because the factory amplifier provides power the stereo location. (power enters the amplifier though the blue plug and leaves to the radio in the green plug) So you would have to either 1) cut the speaker wires out of the plug, or 2) run new power wires (batt, acc, dimmer) to your radio, bypassing the need for the OEM amplifier to provide the power. Then you could just leave the the blue and green plugs detached... but you still need to splice onto the green plug for speaker wires though.

Morning and thanks for responding. Well, through a lot of research, a few tech support calls and diligence, I analyzed the wiring diagrams and know exactly which wires that were cut from the original Toyota radio plug twh15 do what. It took several hours of trouble shooting with resistant tech support people, but I believe I have it now. I'm going to try it in the morning and see if it works. If it does not work, then my only conclusion is that the factory amp blew. I will post my findings after I try it for anyone who may have this same scenario. The most comprehensive wiring diagram I received was from Metra tech support, when I reached out to them about connecting their 71-8112 harness to the radio connector wires that were there from the cut plug twh15. Thanks again Carck

 

Somehow, i totally missed the part of your original post where you were already aware of the metra 71-8112, hehe.

I'll be interested in your findings. This seems to be common enough question where I thought about making an inferred (non-fsm) wiring diagram that should be friendly to share on the forum.

 

Yeah. I just wish the people I purchased the car from had disclosed everything. Going to do my best to get everything right then go from there. Will keep you posted

 

Hi Jigg007. Thought i would give you an update on my progress with the aftermarket radio installation. I was fortunate enough to find a very nice guy who was parting out a 97 avalon with the factory amp system and the plug i needed behind the factory radio. It was exactly the plug i needed, see pics and helped me as a lay person get an even better understanding of the wiring diagram. The good news is, with the 71 8112 metra plug, i did wire it correctly to the cut off plug wires, however as soon as i tried to power up the radio, it blew the 7.5 amp radio fuse in the engine box. My next step is to try and locate a short, which i figure will probably between the antenna motor and relay in the trunk area or one of the brown grounds. Im going to try my best to find the short. Another forum user had asked the question about the same color wires with either 1 gray dot or 2 dots along the length of the wire. Looking at my original oem plug, i figured out that the 2 dots was speaker wire. What a pain this is. Will keep you posted. Carck

 

Alls good with the radio. Turned out to be an easy fix as I had the rad cig .5 amp interior fuse in the wrong slot, which is why the radio did not power up. Still bypassed the factory amp and ran all connection to radio and amp harnesses. Now onto the next problem. Stay safe

 

Hey good post and pictures, I'm trying to do the same on a 98 avalon xls with what I believe has the same setup with the amp and speakers and was wondering if you had any pictures of what you 2 amp harness plugs looked like after you spliced into them. I just need power from the harness of the amp going correctly to a aftermarket stereo I'm trying to put in and was curious how you solved that problem.