S4 temperature gauge/sensor

[TomCrox41]

Hello Ladies and Gents

I need knowledge...
I had a fluctuating temp gauge and corresponding fault code recently. So I put a new sensor in. That fixed the code but then found car was not getting up to temp. At this point I suspected thermostat.
I fitted a thermostat today, no improvement in temp.

reading temperature with vagcom from engine shows correct coolant temp (85-90 ish deg). So why is the gauge only showing 69-70ish under normal driving???

I pulled battery for 10mins to reset. No success.

Any ideas? Does the sensor need to coded? Or reset?
Car is 2004 S4 4.2

Cheers
Tom

 

[Mike B]

did you use a genuine sensor?

 

[TomCrox41]

It was a OEM sensor with the correct PN. although brought from flee bay. I was thinking same thing but surely if it was a bad sensor vagcom wouldn't read right?.?.?¿

 

[Jimmy TDI]

You could have a working stat and sensor, it could be the temp gauge that's faulty.

You can test the function of the clocks by doing a needle sweep in the system functions test.

 

[Scott0583]

My temp via torque pro on my phone always comes up with temp up to 90 long before the needle. Strange.

 

[TomCrox41]

can you do a needle sweep test on a B6??? i didnt think that was possible....

when i access the instrument panel in Vagcom and look at the coolant temp it says very similar to what the needle shows.

So does the instrument panel get different information to the Engine??? different sensor?

 

[Scott0583]

On my old car it had two sensors one for the dash and one for the ECU. And that's much less technological. So I suppose that it could be the same here.

 

[TomCrox41]

Interesting. Just been looking on at diagrams, and it suggests that the temp sensor is a 'dual temperature sender'.
So..... is it possible that the two circuits within the sender are feeding different things, one to ECU and one to dash?????

Me thinks im gonna get another one from Audi.

 

[Mike B]

I would always fit a genuine one.If the dial is right you should be able to tell if the engine isn't getting hot as soon as it should.Its unusual for the dial to fail being fairly crude and simple

 

[pauldazzle]

Interesting. Just been looking on at diagrams, and it suggests that the temp sensor is a 'dual temperature sender'.
So..... is it possible that the two circuits within the sender are feeding different things, one to ECU and one to dash?????

Me thinks im gonna get another one from Audi.

Yes the CTS has 2 outputs i.e. 1 to the ECU & the other to the gauge. It is common for one output to fail. Aftermarket CTS's are notorious for not working correctly. Fit a genuine VAG CTS only.
Buy cheap, buy twice!

 

[Jimmy TDI]

Yes you can do a needle sweep test on a B6 as I've done it myself.

As said above its a duel sensor, and if you have a tps local to you try them first as they're £25+vat as opposed to £40+vat from audi.