Chainds

I am trying to resolve a P2181 code by replacing the coolant sensor. I know this question has been asked before, but I have not been able to locate the coolant sensor. I have found plenty of threads and pictures that show it near the firewall and I can even find that location on my car, but the location on the plastic housing is blocked off. I have been advised by an audi tech that it has been moved "near the radiator." Any help would be appreciated.

Also, I assume I am looking for a two wire connector on this sensor.

Please help Obi-Wan, I have been looking for so long...

mister pepper

Is P2181 commonly the sensor? I have that code a well (accompanied by the temperature needle not always coming up to temp as you would expect) and assumed that my problems were caused by a faulty thermostat not closing all the way. I'd be happy to replace the sensor to fix my problems, rather than swapping out the water pump/thermostat assembly I have sitting in my garage.

Chainds

===================================
I have spent a lot of time trying to decipher the various stated causes for P2181. I don's see anything strange on my temperature gage nor anything performance related. The car seems to have lots of electrical gremlins, so I am going after the easy/inexpensive stuff first. I do think I have found the sensor I am interested in. Hidden under the intake manifold. As near as I can tell the manifold will have to come off, so I am waiting for enough time to finish the job.

Moviela

P2181 could be the sensor, but usually not. It is under the intake manifold on the water pump assembly. The water pump is a black plastic unit that is driven from the rear of the engine by a timing belt. It is easy to replace if you remove the intake manifold. You will need one triple square bit to remove one brace. Other tools should already be in your tool box. Clean the intake while the manifold is off.

Back to P2181. It is usually a stuck thermostat. You need a new one. The rub is there are two types. One from Europe, the other from Korea. Best to take the pump off to see which one you need. My car VIN said I had the Korean version, but there was a Behr in there. The two are not interchangeable.

I invite your attention to this excellent thread with pictures:

B8 A4 2.0 TFSI: DIY Water Pump Replacement

oaktreelimb

Engine coolant temperature sensor is mounted on water pump / thermostat assembly.
Most likely your car has thermostat problem. I would get new water pump / thermostat assembly from dealer. New water pump comes with New temperature sensor.

mister pepper

Wouldn't a stuck (open) thermostat cause the temp gauge to read cool? Mine does, although it seems to read normal most of the time now. So is it just the thermostat that is either Korean or European? I figured it would be just as easy, and have a lower likelihood of user-caused leaks, if I went ahead and replaced the entire water pump assembly. It's sitting in my garage while I wait for a good time to install it. But now I'm worried that it won't fit. It should include the thermostat as well, presumably the correct one for the assembly. Should I be good to go? Is it worth replacing the thermostat in the one I take out (otherwise fine, but with 110k miles on it) to keep as a spare?

Msponseller

But is there any more info out there as to where the sensor is?

SMac770

The coolant temp sender? It's in the coolant pump. Lots of information out there.

youtu.be/K3TfykE4uFo?t=48

Temp sender is on the upper left of the coolant pump as pictured there, with the 2-pin electrical plug. Thermostat is a purely analog operation, located inside the rearward large pipe at the bottom.