[A4] Engine Coolant Temp Sensor

Peter Kirby 4pkirby at gmail.com
Tue Apr 22 05:40:21 PDT 2008

I'll admit I based myself on previous Audis (10V90 and 20V90) when I
said there were two sensors.  I looked at the wiring diagrams in my A4
Bentley last night and it seems to show both a G2 and a G62 ECTS but
it's possible that there are two sensors built into the one unit -- I
don't know.  Bentley does include a test using a VAG-COM that should
be able to narrow it down.  If you don't have free access to something
that can read the output blocks (VAG-COM or PRO-DIAG) you may have to
get the dealer to check it out.  Make sure that they read the output
block for that sensor and not just checking for error codes.


On Mon, Apr 21, 2008 at 1:58 PM, Jim Coleman <jacolemn at rochester.rr.com> wrote:
> I looked through Bentley manual, searching on ECT and could find only one
>  sensor located at the rear of the head in a coolant hose. And the wiring
>  diagram shows only one sensor with the wire going into Control Panel Module.
>  I don't have any CEL, just a funky gauge. Hate to call the dealer and ask.
>  Maybe I'll hang on until the last couple of hundred miles and see if a CEL
>  shows up.
>  Jim
>  -----Original Message-----
>  From: Peter Kirby [mailto:4pkirby at gmail.com]
>  Sent: Monday, April 21, 2008 8:14 AM
>  To: jacolemn at rochester.rr.com
>  Cc: A4 Mailing list (E-mail)
>  Subject: Re: [A4] Engine Coolant Temp Sensor
>  The ECTS that is covered by the extended warranty is the one that
>  sends a signal to the computer, NOT the one that drives the
>  temperature gauge.
>  I just had my ECTS replaced by the dealer under the extended warranty.
>   My gauge was fine but it was sending a CEL any time the outside
>  temperature got above about +3C.
>  Peter
>  2001 1.8tq A4
>  On Thu, Apr 17, 2008 at 4:51 PM, Jim Coleman <jacolemn at rochester.rr.com>
>  wrote:
>  > The question is for an 2002 A4 with 1.8L Turbo motor. What is the current
>  >  opinion on the need to replace the Engine Coolant Temperature (ECT)
>  sensor?
>  >  Ours was acting strangely in that when starting up with a cold engine
>  heat
>  >  would be coming out of the heater but the dash gauge would be pegged on
>  >  cold. Then It would go partway up and return to cold several times
>  finally
>  >  returning to normal (middle of the dash gauge) after about 10 minutes of
>  >  operation. I was about ready to replace the sensor when we took the car
>  >  south on a trip to Florida where it was in a warmer climate for a few
>  months
>  >  and the symptom went away. It  seems to work fine now. Then a letter came
>  >  from Audi stating that the ECT was now warranted to 100K miles due to
>  >  failures. We have 98,600 miles on the car now so the ECT warranty is
>  almost
>  >  over for us. So should I go to the very inconvenient Audi dealer and get
>  it
>  >  replaced? There was never a CEL or any other indication. Will they
>  replace
>  >  it even though it seems OK now? If I wait, is the ECT sensor very
>  expensive
>  >  it I have to do it myself later outside of warranty?
>  >
>  >  Some of you on the list must have had a similar symptom. What would you
>  do?
>  >
>  >  Jim
>  >
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