307 hdi 2004 anti polution error

Oh dear, it has happened again. Engine warning light comes on straight away
and with it the Antipollution error. Then the car runs very badly. Also, the
battery goes dead after a couple of hours standing (nearly new battery). The
battery problem has occurred at the same time as the error message. But,
there is history!

The same thing happened about 8 months ago and it took an age to discover
the problem with Peugeot telling me to change all the heater plugs.
Eventually an auto electrician discovered that the heater plug relay had
burnt out causing a short that deadened the battery and caused the same
error.

My question is how can I test the relay without buying a new one and is it a
well known or common problem that the relay doesn't last very long?

Another question, maybe but maybe not related is that sometimes when driving
along normally the car will suddenly start to judder quite badly for a few
miles as if it is only running on 2 or 3 cylinders. The it will right it's
self and I might get another 30 or 300 miles before it happens again. During
this problem there is never any error message or error light. I have also
noticed (but it might be quite normal) that there is always quite a build up
of soot on the bodywork above the exhaust exit pipe at the back of the car.
I am sure that this is more that normal.

Any thoughts or experience with these problems and I would love to hear from
you before I spend another £400 trying to get the car repaired.

Cheers
Lenny

 

forgot to mention....
307 SE Hdi 110, Deisel, 2004. Updated software (because of fan over
running). Fully serviced. Particulate filter fluid topped up 10000 miles ago
and reset.