On an 8 hour drive yesterday I found there's a data display easter egg in the 300C Electronic Vehicle Information Center (EVIC).
There are 7 pages of additional EVIC data you can access by pressing mode (music note) and compass on the steering wheel simultaneously for about 10 seconds. Use the leftmost Up/Dn arrows to scroll through the pages.
Page 1 - CCN SW P/N
Page 2 - Speed/RPM/Coolant Temp/BattV
Page 3 - Temp_AVG/Temp_RAW/Pedal_Position
Page 4 - Compass/Compass_RAW
Page 5 - Left/Right fuel tank level info
Page 6 - last VTA trig (???)
Page 7 - Chime request info,