Loss of L/100 info after stereo upgrade or battery disconnect

[Malicious]

Have seen a few issues with installation of after market stereos losing the trip functions on the dash

This is the connector in the steering column the black wire on the left is earth and must still be earthed for the button to work.
It appears to feed via the audio system and can get disconnected .

Second if for some reason the trip functions vanish press and hold "i" to reset it

 

[Old.Tony]

So they haven't yet isolated the earth from the stereo - it can still cause problems! Good to know, thanks!