i did a search but no one has this problem. i never pull the codes yet but my check engine light just came on my 00 S40 1.9T and at the same time mt A/C is not working anymore and the temperture gauge spike up to the red and came back down. there was no way the car overheated that fast. also when i turn off the car the radiator fans stays on. can anyone help me???

 

Yes most likely a bad coolant temp sensor. Check the thermostat as well.

 

I just recently had the same prob....Get it fixed as soon as you can, best bet like tech said, change sensor AND thermostat, need not take a chance at payin more later when you can do it all at once... Dealer price was bout 280 or so, but under warranty, but u needto do it quick as i had all kinds of probs beyond what u have such as car overreving, not starting after turned off, many others.....Good luck, it's a beautiful car and this minor issue is worth the vehicle.