2003 Stock Stereo NOT Compatible with Newer Models.
The buttons on my 2003 stock stereo (150 k miles) started working intermittently. The display is completely erratic. You can always get the unit on and off, and it will play the one radio station it is on. It reponds to a hard indicator like inserting a CD plays from beginning, but none of the buttons control it. If you plug in an aux cord it will automatically activate, but none of the AM FM CD AUX buttons will do this. Occasionally the buttons all work briefly, but not for long. It seems temperature/humidity sensitive. As it warms up or cools down there is a brief window of operation.
I bought a salvaged 2005 unit for $65 that has the additional XM buttom on it. Once you take the 2003 unit out of the dash (Easy YouTube video on this), you will see the aux plug for the older unit looks very similar to a standard earphone jack.
BUT, the newer 2005 unit has a small rectangular aux port that is not compatible with the 2003 wiring jack. I installed it without the aux plug and it worked EXCEPT no radio signal because the antenna functionality is included in that aux wiring.
I had to send it back.
I get minimal functionality and am getting by just fine. Will find a salvaged 2003 stock unit at some point.