After some really heavy rain here in England, I got the classic message:
Passenger Door Open! - which was really annoying as it doesn't go away once you drive off and prevents central locking with the fob etc.

So I dutifully went and purchased a secondhand door latch, thinking that I would change said latch and be done with a faulty micro switch.

After removing the door card though, I thought it best to clean out the 17(?) pin connector before I started and this magically sorted out the problem!

If you open the connector, you may even find it loaded with WD40 from your attempts at clearing the microswitch earlier, so clean that out first with electrical cleaner (alcohol based stuff), blow it out with compressed air and then once it's properly dried out, place some silicone grease in the connector before you place the two pieces back together.

Job done!

 

Good job!