So i got me a 2001 s40 and the temp sensor failed and i replaced it, it was fine for a month and now it just failed again, i don't want to have to replace the sensor every month, is there any other possible reasons it might be failing because it shouldn't be affected by anything since it just changes resistance depending on temperature...

 

Your temp sensor is not going to "fail every month" (unless you bought the cheapest part you could find). But It might set a code every month until you find the real problem. Do you have any more details other than "I got a code, replaced a part and got the same code again"? (A code does not mean the sensor is bad, it means the signal sent is not what is expected)

 

I can not really explain it but the temperature value wildly fluctuates like in this recording

 

How about corrosion or a bad connection - or a 20 year old wire with missing insulation touching something or grounding out? Nice looking graphing software. What scan tool is that?

 

The scan tool is a elm something i cant recall the name but its really good and i really recommend it