Reddit reviews BMW (82 11 0 149 389 Audio Auxiliary Input Cable

I don't know about the Avalon specifically, but its possible in many cars. You'll have to exercise some Google-fu.

A whole bunch of factory head units, especially on nicer cars starting in the early 2000s, have aux inputs on the back of the unit. Before an aux input became a standard equipment expectation, it was often a dealer-installed option (i.e. plugging in and running an aux cable) or used to wire up a CD changer (which you can often unwire and replace with an aux in).

For instance, here's what I installed in my car: http://www.amazon.com/BMW-82-11-149-389/dp/B000PA00XM#productDetails. $36 on Amazon for OEM, or you can hunt around on eBay or other smaller sites and probably find an OEM one for $25 or a knock off for $15. Literally just plugs into the back of the unit, then you run it to wherever you want, but typically the glovebox is easiest.

Optionally, I also discretely mounted a small ~$40 bluetooth/A2DP receiver (this guy, much nicer than OP, gets power from the car and also doubles as a USB power plug) on the dash next to the stereo and ran its wire under the trim into the glovebox to connect to the 3.5mm aux. It works/sounds great and I mostly use the bluetooth since its nice to not have to fiddle with wires every time I get in/out of the car, but I can also unplug the bluetooth and plug straight in to the 3.5mm plug in the glovebox.

I'm not entirely sure if you it will work in a 2004 or not but I installed this bad boy amazon in my 2006 325ci about two years ago and it still works like a charm.

This: http://www.amazon.com/BMW-82-11-149-389/dp/B000PA00XM

Hook your iphone/ipod into the aux input.

You might need these: http://www.amazon.com/Leegoal-Panel-Dashboard-Dismantle-Installer/dp/B00D7XNQHG/ref=sr_1_3?s=automotive&ie=UTF8&qid=1452048112&sr=1-3&keywords=panel+removal+tool

And watch this for how to install it: https://www.youtube.com/watch?v=0qmXdnFdjwk

I found this job to be pretty easy. I installed in the back of pocket below the radio. I can tuck the wire away that way.

Everyone is right about the maintenance. Stay on top of it or it will get out of control.

How to tell if you have DSP. You will need the BM53 radio to add auxiliary to have Bluetooth streaming. Buy used on eBay. For non-nav vehicles, the radio is located in the dash (with the amp in the trunk), beneath the little flip-up panel and behind the MID. It's pretty simple to upgrade. BMW sells an auxiliary input retrofit kit for the BM53 radio. Pair that with an aux->Bluetooth device that you can keep in the glovebox.

Personally, I would just go for the aux. Save yourself a ton of money, and don't worry about the bluetooth pairing. If you're dead set on bluetooth I apologize for not helping in that field. I don't know much pertaining to it.

Here is the aux kit: http://www.amazon.com/BMW-82-11-149-389/dp/B000PA00XM

Thats spot on. I figured i was pretty lucky in that regard. Good on BMW to allow that to happen though. Here is the cable that i am using right now in my car. Not too pricy, and the install wasnt much of a hassle either.

Take a look at your radio model number and compare it to the model numbers in this thread about aux-enabled radios. If you have one that is aux compatible, getting [an aux adapter] (https://www.amazon.com/BMW-82-11-149-389/dp/B000PA00XM) and routing it to the front isn't too difficult - just pull out radio trim piece, radio, AC unit, sunglasses tray.

I ended up drilling a hole in the bottom of the center console panel (empty space next to the passenger heated seat button) and pulling the aux port there, since I found that was much easier to reach than the glovebox.

If your radio is not aux-compatible (they all have the port, just some don't have aux mode enabled), you could always go for the GROM or similar units (the £150 fancy adaptor that they were talking about), use an emulator, or you could splice into the CD player lines.