P2181 - Coolant Malfunction...Coolant temperature sensor

[clemsongt]

I have had the P2181 MIL for a while now, and have yet to figure out what the problem is. The options that I have seen as a possibility are: low coolant level, water pump, thermostat, fan switches, coolant temperature sensor (CTS), and coolant level sensor. Since my car has not overheated (needle stays right in the middle), both fans run at idle, and my coolant level is fine, I have looked not looked at the water pump or thermostat.

I cannot remove or inspect the coolant level sensor because it is built into the reservoir tank. If anyone has any suggestions on how to test it, I would appreciate it.

I have not been able to find much information on the CTS for our engines, I believe the part number is 06A919501A for our car, but I cannot figure out where it is on our car. This thread says that it is just under the fuel pump on the transverse mounted A3 2.0T. I assume that means it is up against the firewall for me. Even with this, I cannot seem to figure out where it is. If anyone can give a little guidance (a picture is worth a 1000 words here), I would appreciate it.

Any other suggestions as to the P2181 problem would be greatly appreciated. I am also going to post this in the 2.0T forum on VWvortex.


EDIT WITH MY SOLUTION:
I am unsure what the exact problem was that caused my P2181 MIL to appear. During an oil change, I noticed a white powerdery residue on the bottom of the crank pulley housing seen here. I eventually figured out that this was dried coolant. From the location, the only logical explanation was that it was a slight water pump leak. Since the leak was so small that I hadn't even noticed a loss in the reservoir, I let it go for a while.
When winter came, I realized that it was taking a while to reach temp. This is indicative of a stuck thermostat.
During the following summer, when I finally got time to work on it, I did an entire timing belt change and replaced the water pump and thermostat while I was at it. The code has not come back. Whether it was tstat or water pump leak, I am unsure, but I am sure it was one or the other. If I had to guess, I would guess it was the thermostat given how slight the leak was (added a few ounces of water once in a years time).

[makav3li]

Does you coolant temperature gauge work? Like upon startup its at 0 and slowly gets up to half way?

[bez101]

the CTS is against the firewall
hard to see just feel for the wires and plug
id take a pic but it realy wont show you anything

but if your gauge is working and sitting at 90 in the middle id say its not that
could be the stat

18613/P2181/008577 - Performance Malfunction in Cooling System
Possible Solutions
Check Engine Coolant Temperature Sender (G62)

Check Coolant Thermostat
Check Engine Cooling System
Put the key on, fan speed on 1, and push the a/c switch. Are both fans kicking on? If not, you found the problem.
Put the key on and fan speed on 1. Does heat come out readily from the vents?
No. Probably the water pump is gone.
Yes. Probably the thermostat is gone.

[clemsongt]

Update:

the CTS is against the firewall
hard to see just feel for the wires and plug
id take a pic but it realy wont show you anything

but if your gauge is working and sitting at 90 in the middle id say its not that
could be the stat

I stumbled around under my hood and may have found it. This was on the rear or the block just above the catalytic converter on the passenger side. Let me know if this is the CTS.

18613/P2181/008577 - Performance Malfunction in Cooling System
Possible Solutions
Check Engine Coolant Temperature Sender (G62)

Check Coolant Thermostat
Check Engine Cooling System
Put the key on, fan speed on 1, and push the a/c switch. Are both fans kicking on? If not, you found the problem.
Put the key on and fan speed on 1. Does heat come out readily from the vents?
No. Probably the water pump is gone.
Yes. Probably the thermostat is gone.

^^I had a link to that in my first post, but what in the world does it mean? "Put the key on, fan speed on 1, and push the a/c switch. Are both fans kicking on?" Is that supposed to be when your car is warm? I don't know any car that turns on the radiator fans with the engine off and cool. What is the a/c switch? Would I just have the econ mode pressed and then unpress it?...I also don't know any car that puts heat out of the vents when the car is cool.

[ECS Tuning-Audi]

Yes this is a coolant temp sensor for your car. As for location, hope this diagram helps:

[bez101]

thats the CTS
and it means put your ignition on 1 first click if the fan comes on then theres your problem
do you get hot air ? this is when the car is warm
its just a guide for a few things to check to narrow it down
the ac means have your aircon on ie econ off and your aircon fan will turn on

[clemsongt]

Thanks for the responses guys. Another question: How much coolant does our car hold? I'm thinking about draining it and doing a flush (I know, I know...lifetime fluid), and seeing what happens. There was a lot of crap in the reservoir the other night when i cleaned it out, so I'd imagine there might be a lot of crap in the rest of the engine as well.

[ECS Tuning-Audi]

Thanks for the responses guys. Another question: How much coolant does our car hold? I'm thinking about draining it and doing a flush (I know, I know...lifetime fluid), and seeing what happens. There was a lot of crap in the reservoir the other night when i cleaned it out, so I'd imagine there might be a lot of crap in the rest of the engine as well.

I'm always a fan of coolant flushes in these circumstances. Lifetime or not - it can get dirty and start oxidizing. You will need just under 3.0L of coolant for a full flush. If you are doing a full flush, you have a couple of options here as well: G12 G12 plus and G12 plus plus.

[clemsongt]

Thanks again Chris. I have a follow up question. Where's the picture you posted from? That looks like a different sensor than what I showed in my picture. Am I wrong, or is that off of a different car (transverse mounted or something) causing it to look different?

I'm always a fan of coolant flushes in these circumstances. Lifetime or not - it can get dirty and start oxidizing. You will need just under 3.0L of coolant for a full flush. If you are doing a full flush, you have a couple of options here as well: G12 G12 plus and G12 plus plus.

And by 3.0L, I guess a 1.5L bottle and 1.5L of water is what I need.

[ECS Tuning-Audi]

It may be a different car, but it is a 2.0t block so the sensor is in the same location on your block. I'm afraid I don't know where the source image is from, many times I just "save image location" when people make pic requests. That way I have a "database" of pictures in my arsenal.

As per coolant, it depends on what you order in terms of diluting or not diluting.

[clemsongt]

Has anyone pulled a temp sensor? Would I need to drain fluid first, or would it be OK to remove it without draining any fluid? Is there any difference between the sensors shown in the pictures in post 4 and 5?

[ECS Tuning-Audi]

You shouldn't need to drain the system and the sensors should be the same. They have been using the same CTS for generation upon generation of Audis now.

[clemsongt]

You shouldn't need to drain the system and the sensors should be the same. They have been using the same CTS for generation upon generation of Audis now.

Thanks...but I don't think you quite get my question...what your picture points to and what my picture shows are two different things (They don't look the same). I can't seem to find what your picture is pointing to.

[ECS Tuning-Audi]

ETKA shows it on the thermostat housing with the coolant temperature sender in the side.

[clemsongt]

'Preciate the help. I wanted to give an update on the sending unit in case someone comes along and is still a little confused. The picture I showed in post 4 is of the sending unit. I was able to work ETKA well enough to confirm this:

This is a picture showing the part mounted to the block that holds the sending unit (CTS):

This is the illustration showing where the 'water connection' is in the grand scheme of things:

Less zoomed in than the picture above:


I guess if/when I figure out what is causing my P2181 error, I will relay that information back here just to add more info to the archives.

[clemsongt]

New thought and new question: How long does it take you guys to get up to operating temp? (I'm wondering minutes here). Next time anyone goes out for a drive if you time how long it takes the needle to point up, I would appreciate the info.

[ECS Tuning-Audi]

4 - 9 minutes depending on ambiant temp.

[bflinn]

Anyone have a problem where temp gage goes dead when warning light comes on. Then when reset the code, temp gage works again...but just for a day or two?

Help appreciated...

Thanks

[billyhoyle]

Clemsongt, any chance you found a solution? I got the P2181 error code tonight and am starting to do some research.

[-Boosted-]

I just got my car back from the dealer after having the same P2181 code stored. Their diagnosis was "sticky thermostat" not allowing the engine to reach optimum operating temperature. I am going to replace both the thermostat and CTS this weekend.

[clemsongt]

Clemsongt, any chance you found a solution? I got the P2181 error code tonight and am starting to do some research.

Solution added to original post. I try to be good and go back when I find a solution, my apologies for missing this one.

[billyhoyle]

Awesome, great contribution to the community!

I'll have to go have a look and see if I'm leaking anywhere. How long were you driving around with the MIL? I'm not quite due for a timing belt job, so I'm hoping I can wait until the spring and do it then. Meantime, I'm going to replace the coolant temp sensor (ECS has a few here for anyone that's looking) and see if that has any impact.

[ECS Tuning-Audi]

Awesome, great contribution to the community!

I'll have to go have a look and see if I'm leaking anywhere. How long were you driving around with the MIL? I'm not quite due for a timing belt job, so I'm hoping I can wait until the spring and do it then. Meantime, I'm going to replace the coolant temp sensor (ECS has a few here for anyone that's looking) and see if that has any impact.

Thanks for posting the link!

Jason

[clemsongt]

Awesome, great contribution to the community!

I'll have to go have a look and see if I'm leaking anywhere. How long were you driving around with the MIL? I'm not quite due for a timing belt job, so I'm hoping I can wait until the spring and do it then. Meantime, I'm going to replace the coolant temp sensor (ECS has a few here for anyone that's looking) and see if that has any impact.

I drove for quite some time - maybe a year, because I could not actually identify what the cause was. Although over that time it was probably only 5-10,000 miles. Once I realized I had a bad Tstat that winter and at 80,000 miles was near a tbelt change, I went ahead and did it all and it went away.

I eliminated the coolant sensor as a potential cause because my gauge never failed as bez101 said. It was always working properly.

[Arecki]

Has anyone ever found the green coolant sensor?
I replaced the thermostat and gray 2pin sensor but my engine light is still on.