For those who have older Audi with AMI (Audi Music Interface) unit installed, we tend to get stuck with a 30-pin iPod and iPhone original AMI cables. There are many part numbers for each type and year of the car, but by playing and modifying AMI cables, I found out that they’re basically the same, the only thing different is the resistors detection. All 3G cables have detection resistor (pin21 & pin22) ~18.7k and 2G ~ 1.87k. When the resistor detection is less than 900 ohm – 0 ohm, the AMI changes to Auxiliary mode which will turn off the USB power and play whatever on pins 1,2 with ground 3. By design, the resistor detection will go to Auxiliary mode with value of 1k ohms for all version. Anyone can convert 2G to 3G cable or vice versa by changing the appropriate detection resistor because the connector internal pins are basically the same.

AMI can only play either AUX (Bluetooth) or USB or iPod and not all at one time. So if an Ebay cable has both AUX (Bluetooth) and USB or 30PIN connector will not work. If you want to switch between AUX and iPod, you need a switcher between 1.8k (iPod) and 900 ohms (AUX)

How To Modify AMI Cable

How To Modify AMI Cable to Stream Music with Bluetooth

To make a USB female power cable for USB dongle and relay (auxiliary mode) power when plugged in.

Get a female to male USB extension or a bulk female, but it’s better to get the extension an try to splice out the 5V and Ground line for the relay.

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