07' Accord Aux Port Install

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The Story

I recently got an 07', 4 Door, V6, 6 Speed, EX-L Honda Accord. I've read that the V6 Accords with a manual transmission also have all available upgrades except for the navigation system as a standard package. After about a month I love the car. It's a blast to drive and the interior features are really nice. The only issue I have is there's no auxiliary port to plug in my phone or an ipod. You can buy plug and play adapters for this, but they seam to average about $80. Why spend $80 when I could get the same thing for less than $10?

Getting Started

First I have to say there's not nearly enough documentation on the OEM radio and pinout on the interwebs and while there are a lot of forum posts talking about this project I couldn't find one that really brought it all together in an easy to follow complete manner. After a few days of fairly intensive searching I think I've pulled together enough information to give this project a shot.

Documentation Found

This car came with XM radio and there was a trial period of a little less than a month after buying the car. While XM radio is a pretty nice service, I can't justify the subscription cost for something I use less than an average of 2 hours a day. Even if the car hadn't come with the XM receiver, I think the factory radio would still have the 14 pin connector used for XM. This connector might also be used for trunk mounted disc changers, but I'm not sure about that. After some searching I was able to find this pinout for the XM connector that someone uploaded to install bay at www.the12volt.com.

OEM Radio XM Connector

A quick Google image search will show you that the tip of an aux cable is the Left channel, the next rung is the Right channel, and the final rung is Ground. I picked up a 5 pin 1/8" audio jack from radio shack for less than $3, part number 274-246. Below is a schematic representation of the jack to be used.

Aux Jack Pinout

Note that with out an audio cable plugged in pins 2 and 3 are shorted together as are pins 4 and 5. When an audio cable is inserted in the jack the cable makes connections to pins 1, 2, and 5 or Ground, Right, and Left signals.

Radio Shacks are harder to find these days. Here's an alternative, 3 pin jack from Amazon.


Direct Radio Connection

Connection Through XM Radio

The second setup will attempt to tie in the aux jack along with XM radio. If you're going to attempt this project I recommend buying a wiring harness to go between the XM connector and the Head Unit plug. You should be able to find on online for a couple bucks. I don't plan on using XM so I cut the factory harness. If I ever want to use XM I'll just open the console back up and rewire the connection. First I cut the R+ and L+ wires only. When I turned the radio on with the aux jack plugged in I could still hear the XM radio. When I turned the radio up I could hear that there was music coming through the aux jack too. I then cut the R-, and L- wires on the connector and left those disconnected.

Factory XM Harness Cut

Now when I turned on the radio I could hear the music from the aux port pretty well. One thing to note is that the music from the aux jack came through a little softer than the radio or CD player, but the quality is still good. Here's the connection schematic.

Aux Jack Connection Through XM

After taking a little road trip I decided I wasn't happy with the softer sound when using the aux port. So I opened the dash back up and tried a couple things. First I connect the L+ and L- pins together from the Aux port going back to the Radio. This just made the sound even softer, barely audible even. Then I connected the L- to Ground and noticed that the sound seemed to get a little better. So I tied both L- and R- to Ground and sealed everything back up.

Full Connection Schematic

There are a couple more features I've thought about adding, but have not done so yet. First if you wanted to keep the ability to use XM Radio you could easily add a 4PDT (4 Pole Double Throw) switch to this circuit as shown here.

Full Connection Schematic With XM/Aux Switch

These switches come in varying styles, sizes, and prices. You can find them at Digikey.com among other places. You just have to figure out what works best for you.

The other addition I was considering is some kind of ground loop isolation. I've noticed that when I connect my phone to the Aux jack with the charger plugged in I get some humming/buzzing. It's not really noticeable unless I'm listening to something really soft that I have turned up a good deal.

- According to this article at epanorama.net, "A ground loop in the power or video signal occurs when some components in the same system are receiving its power from a different ground than other components, or the ground potential between two pieces of equipment is not identical." That got me thinking that this could possibly be resolved by tying the Aux ground to the 12 DC Charger ground. This should eliminate the different reference points between the charger and the radio/aux ground, which should eliminate the noise. When I checked the difference between the two grounds with a digital multimeter it showed that they are shorted together. I tied the two grounds together and it sounded like the interference actually got worse.

- My next idea is to add some kind of AC filtering on the 12V DC power line. I've noticed that the noise changes as I rev my engine. That leads me to believe it is being generated by the alternator. If I can get a cleaner DC signal to the charger maybe the noise will go away. With any luck this will eliminate, or at least limit the noise generated by plugging the charger in. Stay tuned.

More to Come!

Enjoy and feel free to report any problems or suggestions to longet@spider.dnsdojo.net.