citreon ds3 anti poplution fault

[gun12b]

my daughters ds3 is showing this fault, any ideas to what it could be ??
it had an o2 sensor fitted 6 months ago.
thx in advance

[gun12b]

1.6 2010 plate
borrowed my mates obd, and reset the code all good now.

[gun12b]

the code came back on the next day.
fitted one of these myself, all good now