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View Full Version : Coolant Temp at middle when engine is completely cold



pbcrazy
01-22-2017, 12:33 PM
I have been diagnosing an overheating issue, and I determined it was a faulty aux fan. So I had been unhooking various fuses/testing the fan's 12v source connector last night to come to this conclusion.

This morning I go out and start it up and the temp needle is at the center, after sitting for over 12 hours in ~40F weather. Definitely not right, after 5 minutes of idle it rose up to give the overheating warning. Upper rad hose was warm but not hot, heater was cold, valve cover/block was pretty warm. I tried unhooking the battery but it still went right to center, I think the gauge somehow got calibrated to go to center when it should be at cold. Does anybody have any idea how to fix this?? I don't want to drive it when after 2 minutes it says its overheating (even if its not actually)

OverSpun
01-22-2017, 12:49 PM
Your G2 sensor is out.

Do you have any codes? Could see a code like this in VCDS.


1 Fault Found:
01039 - Coolant Temperature Sensor (G2)
30-10 - Open or Short to Plus - Intermittent

http://images16.fotki.com/v368/photos/4/41970/1982850/OEMCTSG_540-vi.jpg

I replaced mine last year since the entire coolant gauge stopped working from the sensor. These sensors are very inexpensive to try it anyway.

pbcrazy
01-22-2017, 01:06 PM
No codes, but that sensor was working 100% before I started playing with the fuses/fan. It's almost like the gauge thinks that the middle is actually cold, then it rose like normal from there. I actually have a new sensor coming in the mail tomorrow (bought it when I thought that was my overheating issue), but I just need to be able to drive 12 miles to work and back tomorrow and I can't if it is beeping at me that its overheating...

OverSpun
01-22-2017, 01:52 PM
No codes, but that sensor was working 100% before I started playing with the fuses/fan. It's almost like the gauge thinks that the middle is actually cold, then it rose like normal from there. I actually have a new sensor coming in the mail tomorrow (bought it when I thought that was my overheating issue), but I just need to be able to drive 12 miles to work and back tomorrow and I can't if it is beeping at me that its overheating...

I also didn't get a code all the time while the gauge was going erratic. I dealt with it for a couple months before it finally threw a code (I posted exactly what I eventually got). My gauge was working properly sometimes or it would drop to nothing during a drive. It would start working again after restarting the motor (sometimes).