For information, my 306 sits around 90 degrees during normal driving.

Often when an engine fault is detected the car will switch into a "Safe
mode" which limits power etc, but is designed to get you home/to the
garage whilst running within additional limits designed to reduce any
further issues to the engine.

Antipollution fault sound like it's something to do with the emissions
of the engine, so maybe a sensor has failed or something.  The
dealer/garage should be able to diagnose the fault and get it fixed as
it's under warranty.

D

One of the many sensors has either gone closed/open circuit or reported a
value out of it's normal range. In fact, if you unplug any of the sensors on
the engine, including fuel injectors and run the car, it'll report:
"Antipollution fault" It just seems to be a catch all error code. You'll
have to read the diag code from the ECU to find out which of the many
sensors has reported a fault.

If you can - ask the tech for the fault code, and what they did to repair
the vehicle and prevent the fault from reoccurring. Any response along the
lines of "We've reset the ECU and that's fixed it" will almost certainly
mean another trip back to the dealer, and you don't want that outside of the
warranty. (Seriously, the Siemens / Bosch parts on these engines are not
cheap)

Chris