P2181 Code

So I am getting the somewhat infamous P2181 code on a 2006 MKV GTI (BPY engine). I did some research and found that it's either an Engine Coolant Temperature sensor, maybe the thermostat, or water pump.

I replaced the ECT sensor as it seemed easy and wasn't too expensive. I disconnected the battery for a while and it ran clean, but then the code came back in two days.

So I'm thinking thermostat, but that job is more involved and more money (which is tough for me right now). I could go get it diagnosed, but even diagnostic fees are tough for me to come up with at the moment. I was hoping I could describe what is happening and see if the thermostat is the most likely culprit.

Temperature gauge is maybe one unit lower than normal at operating temp. It also never goes above the halfway point.
Not losing coolant, and the heater blows heat just fine.
Getting off the freeway and onto surface streets will cause the temperature gauge to read cooler for a minute or two. It goes down to about the 1/4 mark. Thought that was odd. Continued driving gets the temperature back up after a minute or two.

Hopefully that info points to the most likely cause of the problem. Any help you can provide is very much appreciated.

Sounds like a faulty thermostat. Its not too terrible of a job as long as you have somewhere warm to work

Thanks for the reply eurocars. I've been reading as much as I can, and it does seem like the thermostat is the issue. It's not as simple as an oil change, but it looks straight forward enough.

One thing I didn't find is how much coolant needs to be drained? I'm seeing some say drain it all, some say don't drain any. Just keep the reservoir cap on and remove the thermostat, replace whatever coolant was lost.

I need to replace the timing belt in about 8 months, so if I don't have to dump all of the coolant now, that'll be better since I'm draining it when doing that timing belt. Thanks again.

I tried doing this job before, and gave up on it. It all goes well to the part of removing the actual piece. There is a hard line that goes into it, and you cannot remove it without removing the small flex pipe below the throttle body to get some clearance. Alternator removal is straight forward. It's a lot of money, I ended up paying the dealer to do it :/ Very silly design on these cars. Last 2 vehicles I owned, just opened up a housing, swapped out the actual thermostat and closed it back up. This car is a whole assembly with 3 different outlets you have to remove.

Oh and also I had the same issue and code, cold days temp would go down below normal. Thermostat is the problem.

danman132x said:

I tried doing this job before, and gave up on it. It all goes well to the part of removing the actual piece. There is a hard line that goes into it, and you cannot remove it without removing the small flex pipe below the throttle body to get some clearance. Alternator removal is straight forward. It's a lot of money, I ended up paying the dealer to do it :/ Very silly design on these cars. Last 2 vehicles I owned, just opened up a housing, swapped out the actual thermostat and closed it back up. This car is a whole assembly with 3 different outlets you have to remove.

Oh and also I had the same issue and code, cold days temp would go down below normal. Thermostat is the problem.

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This code popped up on me last winter, I cleared it and it never came back until a few weeks ago. I was already a little leary about tackling this job on my own after reading this I've become even more discouraged!! How much labor did you wind up paying to get it done?

To the OP if you do decide to do it yourself Pelican Parts has a pretty good walkthrough here. I also found this on Youtube. Based on the narrative looks like he was pretty determined to get it done




This one is a little more detailed and makes it seem a whole lot easier.

I had this on my TSI powered 09. The thermostat is inside the water pump and I opted to replace the whole thing. It wasn't terrible but you can't see some of the bolts and have to go by feel.

zrickety said:

I had this on my TSI powered 09. The thermostat is inside the water pump and I opted to replace the whole thing. It wasn't terrible but you can't see some of the bolts and have to go by feel.

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TSI thermostat is placed differently than the FSI's. Quite a different job between the two but still do able on both. I do know labor at a dealership is 3 hours or about $280-300 if you have the parts. I may DIY it this weekend so I'll tell you how it goes

I know they are different, just posted in case someone with 08-09 searches this code.

Good info here, thanks for the replies guys. I'm going to give this a try next weekend if I can get the parts arriving on time. It does seem time intensive, but I do have a backup car if I don't have it all back together by the time I have to go back to work. Sometimes having the backup car is the most important aspect of car repair .

I recently had same code and corrected it by replacing the thermostat. Take the opportunity to clean your intake valves. Once you remove the intake manifold, the thermostat housing is right there and it's an easy job. From what i could tell, doing it from the under the car would be a frustrating nightmare.

I'm seriously considering doing just that. I am due for a timing belt soon, so I may wait to clean the valves then.

I received the thermostat yesterday. I ordered a thermostat o-ring separately, but was surprised to see that the thermostat comes with an o-ring.

Did I buy an extra o-ring that I don't need, or are there two o-rings involved with the thermostat and how it seals to the engine?

only one o-ring

Okay, well I have an extra then. That damn thing cost me ~$6.00. Not a lot, but a lot for one o-ring.

Might as well do the timing belt.

I still haven't installed that new thermostat - mainly because I'm contemplating doing the timing belt at the same time. I'm at 87K miles, so it's definitely time.

I'm looking at various timing belt kits and I'm wondering if anyone has any experience with some of the ones that blend in non-OEM parts. I'm looking at the one on EuropaParts in particular. It's a good price, but some of the key components like idle rollers and tensioner are made by INA.

Anyone have experience with kits that don't use OEM parts? How are non-OEM parts holding up? Saving money is always good, but OEM can be a good idea for some of the more critical components.

Virtually all the components in a timing belt kit are not manufactured by VW. VW has contracts with OE suppliers that actually make the parts and put VW logos on them. These companies sell the same parts under their own brands as well. One example is Continental, who makes the belt itself. Europaparts uses parts from these OE suppliers in their kits.

FYI you won't save anytime by doing the thermostat and timing belt at the same time. They are completely unrelated jobs on different sides of the engine. Better to do the thermostat at the same time you do a valve cleaning, since the thermostat is right there under the intake manifold that you have to remove to clean the valves.