Good luck. According to my ex-dealer there are many, many reasons why
this can happen - and they never managed to stop my 807 giving that (and
many other) fault messages on a regular basis. But, on the bright side,
it never seemed to cause any problems other than being yet another
spurious warning to ignore.

Do a check on google - you'll find that hundreds of other people suffer
the same problem. It is one of the main search terms that brings people
to my website. The only real cure seems to be to get rid of your car
before the warranty expires and it becomes an expensive liability, and
buy a car from a competent manufacturer instead. It's a real shame as
Peugeot diesels used to be very solid engines.

Matt

http://807faults.co.uk