89 trans am

i have a friend who inherited her dads 89 trans am but she keeps having problems with her stock stereo she says whenever the car hits a bump the screen goes blank and then the screen either locks or gives an error message and she says she has to press the mute button twice to get it to work again so i assume it takes a long time for the lock message to come up and she can use it again.....any ideas whether it is just the head unit that is bad or a loose wire?? she is concerned becasue she does not want to loose the stereo controls on her steering wheel so she doesn't just want to buy a new head unit thanks for the help

i would do the easiest and most logical thing first, remove it and check all the connections. its probably the constant 12 volt source is loose so when she hits a bump it becomes disconnected and the memory gets erased and theft lock kick ins.

It may also be that the engine ground strap is broken. Easy to fix, just run a suitably short battery cable from an accessory bracket to the chassis. Voila!