Here's how to hack into your radio to add an aux input to connect your phone or mp3 player.

This method applies to the Honda Accord, but may also be similar for the Civic, CRV and Element from the mid 2000's that did not originally come with an aux input.

Forget expensive aux adapters that cost $30-$100! Add your own for the cost of the 3.5mm stereo cable - $1! This DIY video shows you how to open up the radio, examine the motherboard circuitry, solder and connect your own aux line. Also shown is a second method, that you don't even have to open up your radio - just add it to the CD changer lines going to the radio through the accessory port.

Honda radio's internally use digital data transmission to select inputs. Traditionally, this hack would be easy with a tape player or analog CD player. However this radio uses a digital CD player. Therefore, the radio is the only analog signal that can be hacked into.

Wires are soldered to the AF OUT port on the AM/FM modulator, and automatically override the FM signal when audio is played. The downside is that it's only a mono input.

The second method to getting an aux input requires a Honda accessory plugged into the 14-pin M-bus connector. The accessory, be it an external CD changer, tape player or ipod connector, will use the internal I2C protocol to fool the radio into thinking there's an audio input from the accessory port. We then inject our own signal from our phone/mp3 player. This will give you clearer stereo sound, however at line level volume, so you'll have to crank it up a bit.

Additionally you can add a bluetooth adapter to pair your phone with your car wirelessly. Now you can finally throw away that FM transmitter for some much improved quality sound!

This hack was performed on a 2004 Honda Accord and will be the same for 2003, 2004, 2005, 2006, 2007 Accords.