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Discussion Starter · #1 ·
I think I have a bad CTS again...it was replaced abotu 2 -3 years ago. I was scanning with a Scan tool (using a generic car) and the temp reading was jumping back and forth between 50 and 90*C (125 and 195*F).





Does the coolant temp sensor affect the way the engine runs? I mean does the computer use this reading to determine how to dump fuel? Or is the sensor strictly for the gauge on the dash? The guage on the dash seems to work fine though...no weird fluctuations.
 

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Grinding Gears...gone fishing!
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hard starting or no starting is what it can cause, it is a 2 sided sensor. gauge can go nuts also.
 

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2004 GLS 1.8T
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Does the coolant temp sensor affect the way the engine runs? I mean does the computer use this reading to determine how to dump fuel? Or is the sensor strictly for the gauge on the dash? The guage on the dash seems to work fine though...no weird fluctuations.
Yes, it does affect operation, and this will not necessarily show up on the dash gauge. Two sensors in one module; they can and do fail independently.
 

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Discussion Starter · #4 ·
There are two sensors? How do I know which one failed? Where are these sensors?

BTW, I am not getting any codes related to this.
 

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There are two sensors? How do I know which one failed? Where are these sensors?
You replaced it before, right? That's it. The module contains two independent sensors. Four wires. One runs the gauge, the other reports to the computer. I don't know how to make it any clearer than that.

I don't know for sure, but I assume the one your scanner is reading is the one that reports to the ECU. How to tell if the one that activates the gauge is OK is left as an exercise for the alert reader.
 

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Discussion Starter · #6 ·
I see now, there are two sensor in the same unit that I have already replaced.
Why the hell wouldn't they make one sensor that way you'd know right away if it wasn't reading right...that way it would prevent exactly what is happening now where the computer side of it is screwed up and the guage reads fine...how misleading.

I wonder if the scanner has a hard time reading it properly...maybe I need a VAG-com to confirm its really not working properly.
 

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Discussion Starter · #7 ·
I do not have access to a Vag-com in my area. Is there any test that can be done with a multi-meter? i don't want to buy another CTS and dind out I replaced it for nothing.
 

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The Rubberband Man
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There's a way to check the CTS reading with Climatronic......


Did your '99 come with it?
 

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The Rubberband Man
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btw, on my W8 I have two sensors in two different locations. I've had to replace one of them twice in less than a year!
 

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The ECM needs that temperature data for proper engine management. If it didn't, they wouldn't have bothered engineering it into the system. When my CTS was bad I had some starting issues and some idle issues. I've also had three bad CTS's in less than a year. I may have set the record.:lol:

1999 1.8t 5-spd manual
 

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Discussion Starter · #13 ·
See the thing is that my car seems to run normal...the odd hard start and mileage isn't as good as it use to be. I do not get any codes which is the stupid part because you'd never know there was a problem unless the symptoms were really bad. They should have programed the computer to pick up if the sensor is jump 20 or so degrees difference within seconds indicating it gone.

BTW I got a new sensor today but it was light green coloured one...I asked the parts guy if he was sure because the one I replaced it with last time was a dark green one. Of course he said yeah its the right one...guess what...its not.
 

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Discussion Starter · #14 ·
my car does not throw a code. They should have programed the computer to pick up the faulty sensors.

I bought a new sensor today and the parts guy assured me it was the right one though it was light green (my old one was dark green). Went to install it ....wrong one!
 
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