MIL Code Help

[cain12345]

Ok, let me preface this all by saying I have searched and searched and searched all Audi Forums and google, and can't get the info I am looking for.

I have an 06 A4 that I bought about 3 weeks ago. A week ago it threw a CEL with a MIL of p2181 cooling system malfunction (this happened at highway speeds). My coolant temp gauge had always sat a little over the 1/4 mark (should it be at the 1/2 mark regularly?), and I saw it closer to the 1/2 mark and freaked out. Not thinking I cleared the code, and went to the Audi dealership. They charged me $80 and said they couldn't diagnose the problem since there was no code in the computer, and they couldn't reproduce the CEL. 2 days later it threw the code again at highway speeds.

Paying attention to the coolant temp gauge over the past week I have noticed a drastic fluctuation in it's readings. It does not appear to be related to being at speed or idle, the gauge just seems to fluctuate quite often between the 1/4 mark and the 1/2 mark. Heat/A/C seem to be fine. The car also seems to take awhile to warm up(~8-12 mins while driving...still typically sitting a little over the 1/4 mark), but this is my first Audi so I don't know.

Long story short after all my research it seems to me the likely candidate is the Coolant Temp Sensor...correct me if I'm wrong. I think if it was the thermostat I would see it be more of a change be directly related to driving or idling. Also I'm assuming it would be overheating, which it doesn't at all.

So, I would like some input on that...and also if someone knows of a writeup for changing the sensor. I can find pictures and writeups for the 1.8t engine, the 2.8l v6, basically every model but the b7 A4. I can't imagine that changing out the CTS would be something worth taking to the dealership. Any help would be much appreciated.

[rune]

Ok, let me preface this all by saying I have searched and searched and searched all Audi Forums and google, and can't get the info I am looking for.

I have an 06 A4 that I bought about 3 weeks ago. A week ago it threw a CEL with a MIL of p2181 cooling system malfunction (this happened at highway speeds). My coolant temp gauge had always sat a little over the 1/4 mark (should it be at the 1/2 mark regularly?), and I saw it closer to the 1/2 mark and freaked out. Not thinking I cleared the code, and went to the Audi dealership. They charged me $80 and said they couldn't diagnose the problem since there was no code in the computer, and they couldn't reproduce the CEL. 2 days later it threw the code again at highway speeds.

Paying attention to the coolant temp gauge over the past week I have noticed a drastic fluctuation in it's readings. It does not appear to be related to being at speed or idle, the gauge just seems to fluctuate quite often between the 1/4 mark and the 1/2 mark. Heat/A/C seem to be fine. The car also seems to take awhile to warm up(~8-12 mins while driving...still typically sitting a little over the 1/4 mark), but this is my first Audi so I don't know.

Long story short after all my research it seems to me the likely candidate is the Coolant Temp Sensor...correct me if I'm wrong. I think if it was the thermostat I would see it be more of a change be directly related to driving or idling. Also I'm assuming it would be overheating, which it doesn't at all.

So, I would like some input on that...and also if someone knows of a writeup for changing the sensor. I can find pictures and writeups for the 1.8t engine, the 2.8l v6, basically every model but the b7 A4. I can't imagine that changing out the CTS would be something worth taking to the dealership. Any help would be much appreciated.

http://wiki.ross-tech.com/wiki/index...3/P2181/008577

[makav3li]

yep sounds like a coolant temp sensor, should sit at half when warmed up and 8-12 min warmup time isn't far off.

[cain12345]

Yea I have seen that wiki on the mil code...but that is entirely generic. Check coolant temp sensor, check thermostat.....that doesn't help me diagnose what is the actual problem as I am unsure how to check the coolant temp sensor or the thermostat. Like I said I feel fairly confident that it is the CTS now, but I still have no clue where it is on the car. Any help?