I make you all right, there would be no comeback on the OP. He sold the car to the dealer, it's the dealer's worry if the person they sell it on to gets into an accident and then gets done for having a non-declared map.
Otherwise can you imagine the amount of backdated claims that would be going on!! Knock at the door.....
"Oy.... you know that car you sold to someone 10 years ago?? Well he sold it to someone else, who sold it to someone else, who sold it to someone else, who sold it to me and i've just found out that it was you who stuck that massive air freshener on the rear view mirror which blocked my vision and caused me to crash. Pay up!!"
HOWEVER.... To be fair to Staz he hasn't actually said that the OP would be facing legal action etc if there was an accident. He just said....
"What happens if someone buys the car, has an accident and the insurance company has the car checked and finds the map? They can refuse to pay out and then who's fault is it?"
Which I would read as.... as the OP knows he left the map on and didn't try to inform the dealer then
morally it would be his fault.
Don't think he really meant that he would actually be liable, or at risk of being sued etc.
I could be wrong, but that's how I read it.