2002 Mercury Grand marqui
The horn goin off is the anti thieft system in active mode, try using the key to lock and then unlock the drivers door, if that didn't work then try pushing the 7/8 and the 9/0 keyless buttons at the same time, you should hear the doors lock, then put in your unlock code, that should turn off the alarm. HTH
Thanks I will try that
Search Mercury Marquis Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Mercury Marquis Experts