Hi, I am new to this forum and did Google to get here. I have read tons of threads regarding P2181 coolant system warning here. Here is my situation. My 2008 Audi A4 had this warning popup on 01/02/2015 when Austin got very cold. I just got a scanner to read and erase the code since the engine temperature seems normal in the next several days. However, on 01/12, 01/22 and 01/26, almost the same time, the CEL came on again after I erase the error for each time, the scanner gave me below message:

P2181 01/02
P2181 P 02/02

Is this a repeating P2181 warning happening on these days or just I didn't reset/clear the error correctly?

If it is repeating, I would like to replace the thermostat, but I want to confirm before I open the hood.

Thanks

 

It's likely your thermostat. Is your engine temp "wandering" or pegged in the middle? Your engine temp may be fine, but if it's taking too long to get to temp (stuck open), it will throw that code. It could be the coolant temp sensor and that's a cheaper fix to try first if you want, but on mine, I did that and the code came back. Replaced the t-stat and it's been gone for a while now.

 

Yes, it does wander between the middle and 3/8 position for the first 20 minutes. Does it confirm the thermostat needs to be replaced?

 

I don't know about confirmation, but yes, that is highly suspect of a bad thermostat. That's what mine was doing. It's a medium-skill DIY (lots of write-ups around). I think I paid somewhere around $300-350 at my local indie shop to have them do it. Now, it climbs straight up to the 12:00 position in about 5-7 minutes and pegs there.