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Discussion Starter #1 (Edited)
Hi, I have problem with temp. on dashboard. Suddenly, temperature drops.
When I hooked up VCDS I have two different results:


About 3 years ago, thermostat was changed.

Thanks to all.
 

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sorry I don't have a better technical explanation than this:
there are four wires that come off the sensor.
one pair sends a signal to the dash (or whatever feeds info the dash), the other pair goes to whatever is controlling the air/fuel ratio.
it seems one set (no i don't know if there are two different sensors in the actual CTS, as I have never opened it up) flakes first, and usually its the one that goes to the A/F ratio.
Symptoms of this are that the car doesn't turn over and start right away in cold weather, because the sensor is sending the temps to the controller so the A/F is wrong for the air temps.....after like 20-40 cranks or so the engine is warmed enough that the wrong reading no longer matters and the car turns over and starts.

based on what you are seeing, it seems the information going to your dash is the screwy data

for those of you who know more please feel free to correct me.
 

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To add to what ar393 said:
The CTS is, in fact, two sensors in one housing. There are two separate thermistors.

One sensor is wired to the ECM; it's what you see on VCDS in "Engine" and controls fuel/air ratio, etc.

The second sensor is wired to the instrument cluster; it determines the temperature gauge reading. You see it in VCDS in "Instruments."

They should both read nearly the same. The CTS is a common (and confusing) failure in our cars.

Why didn't they just use a single sensor and communicate the to the cluster? The ECM was pretty cutting edge when our cars were new--drive by wire in year 2000! I suspect the design team (from Bosch) didn't want to take any chances. The cluster was designed by a different vendor, too.
 

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Discussion Starter #6
Ar393 and FrescoGreen01.5 FrescoGreen01.5, thanks! You gave me great help.
I'll find and buy new one.

Best regards!
 

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Also if you have a multimeter / voltmeter, you can test the old sensor to confirm that it is sending out two different signals (thus two different temps).

a quick search will bring up a bunch of videos.
 

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Discussion Starter #8
Since it is cheap and it is realy naccessable (too much time for aproach) I'll try to replace it. Thanks one more time.
 
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