If Aux Mode on your stereo head unit can no longer be enabled, it's due to that the aux port fails to signal the stereo head that a patch cable has been plugged in. This failure occurred when my 2007 Sienna was only two years old.
Here is a simple modification that will enable the Aux mode to work again. You must solder contacts that are set in a plastic connector so good heat in minimal time. This mod does not restore factory functionality; rather it will spoof the stereo head unit to sense a patch cable is inserted into the aux jack full time, aux mode will be selectable whether or not a cable is inserted.
In my Sienna, the aux jack is mounted on one end of a small PC board. The other end of the PC board is the connector that plugs into the console. Remove the “aux jack/pc board” wherever it is. Very easy in my Sienna, not one screw and the panel on the right side popped right off using a credit card from the bottom.
This mod is done on the connector that plugs into the console. The Pin 1–3 are L+, R+ (or visa-versa), then audio common/ground. Pin 4 is the signaling contact. Cut pin 4 flush from the PC board and bend up slightly to clear it from touching any contact on the board. Solder a 3.3K resistor between pin3 (common) and the lifted pin 4 on the connector side. Using a 5K pot, I discovered Aux mode begins to function at approximately 750 ohms. There was plenty of room for the addition of the resistor where the board is housed. Reassembly was literally a few snaps.
I’m back a few years later now and I am VERY happy to hear that this information has helped others to get their sound system working again.
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