Reverse Engineering the firmware on a Kenwood DDX9903S

UPDATE 14 MAR 2020: For discussion, see the Google group. Comments from the old WordPress site have been migrated there.

I bought and really like my Kenwood Excelon DDX9903S headunit. I had it in my WRX, and moved it to my LS430. It supports Android Auto and CarPlay, which I find really useful when driving.

However, it has a nag screen every time it boots up. This got me curious as to how it worked, and see if it could be patched to skip this disclaimer. I figured it probably ran Linux on a SoC, as pretty much everything does nowadays. So I grabbed the latest firmware for it (mine was already updated to it), and started probing.

Extract that and you get 3 folders under S_V2_7_0008_0600/:


Custom Speed app update

I update Custom Speed to 1.1. Changes include: An actual theme (consistent colors) More units New icon 2.0 will include an actual settings page that will allow the units to be selected from an easier control, a setting for keeping the display on, and other minor UI improvements. There’s no ETA currently for 2.0.