My 2000 has just started a little quirk. When you turn the key off...the radio may play for a sec or lots longer. The radio always turned off when the key was off. Anybody else have this going on. The system is all factory. Thanks.
The test will be to see if the radio still does that if he unplugs the inverter.
I have a rechargeable jump starter. It can be recharged by plugging it into a 110v outlet, or by plugging it into the car's DC outlet. When it's plugged into the DC outlet my radio also plays when the engine is off.
Hint Hint!!! unplug the inverter and see if the problem goes away. Problem has been reported before. If something is plugged in the sockets they can feed voltage back causing the radio to continue playing.