Just over a month ago I bought a secondhand 10 plate mk4 Mondeo and I really like it but over the weekend I have noticed a small issue with the Automatic Relocking mechanism on it. It is supposed to relock after 45 seconds if you do not open a door or the boot, however, if the only door I open is the rear passenger side door then it will relock itself after those 45 seconds. If I open any other door then it will stay open and if i open any other door in conjunction with the rear passenger one it stays open.

I've tried re-programming the remote key to open only the driver door with one click on the remote and two clicks open all doors but it still relocks when only the rear passenger door is opened in the 45 seconds.

My issue with this is that the rear passenger side is where our little boy sits so when i'm strapping him into his car seat this is the door i'm going to go to first, and i'd rather not have to open another door before opening that one.

I'm pretty certain i got 3 months 'warranty' from the place I bought it and I'm happy to take it back there but I just thought it would be worth asking on here if anyone knew of a quick and easy fix for this?

Many thanks in advance

the door lock system knows a door has been opened by the activation of the interior light circut, does the rear door activate the interion light? if not it may be a problem with the door light switch.

Yep. The interior light comes on when the back door is open. So the car is recognising that the door is open but it's still locking again.