Tech question - code p2181

Recently bought a 2003 TT; runs grat, but has a check engine light obd code is p2181, which transates to "cooling system performance"- but not very specific.
Contacted previous owner, who has tried the following:
replaced thermostat replaced temp sensor on top of motoron drivers' side replaced cooling fan module (big square thing on the bottomof the motor)
Since we stillhave hte light, I assume none of these were the problem. So - I'm hoping someone else out there can provide suggestions on where to look next.
Second question (possibly related) - sometimes the coolant pump will stay on for over an hour after the car's parked - is this normal?
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On Sat, 17 Apr 2010 10:38:32 -0400, against all advice, something

My '04 doesn't do that.
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I am not familiar with the TTs but I will ask some questions: Did you install the Coolant Temperature Sensor from the dealer? What color is it, green?
How many miles on the water pump/timing belt? I am thinking that the impeller on the water pump might be slipping.
Did you properly dilute the G12 coolant? AFAIK it could be that if there is too much G12 and not enough water, the cooling performance might be poorer. It actually needs the water to perform well.
AFAIK that electric coolant pump should not run that long! I am thinking 20 minutes tops but probably more like 5 minutes.
--
later,
(One out of many daves)
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Google is your friend. Take a look here, maybe it is a simple fix -
http://www.jlaforums.com/viewtopic.php?p=34640531
Dan D '04 A4 1.8Tq MT06 Central NJ USA
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