Catalyst Oxygen (Lambda) Sensor Correction

the light comes on when i was driving and the temp were 4 c

i went to the technician as he scanned with the Vcds and found fault ENGINE and it was Catalyst Oxygen (Lambda) Sensor Correction

-he cleared all the errors and it's been okay for 4 days so far but the problem came with the temp problem when the whether temp is about 4 to 8 Celsius (40 to 80 Fahrenheit) the engine temp goes down and up between 70 - 90.

are this two things related to each other .. and what should i do with the fault Catalyst Oxygen (Lambda) Sensor Correction and with temp goes down and up.???