coolant temp gauge not working, co

The coolant temp gauge does not use the G62 coolant temp sensor that is wired to the engine module. It uses the G2 coolant temp sensor wired directly to the instruments module. Checking G62 in address 01 engine will not help him diagnose a temperature gauge issue as it is not relevant. He needs to check the G2 coolant temp in address 17 instruments. What makes it even more bizarre is both sensors exist in the same part located in the coolant flange under the tandem pump.

Thank you for detailed simplified instructions.
The posted ideas and suggestions have been very insightful.
I asked my son , a recent mechanical engineering graduate, to help with data collection and creating three columns of data 1 top of the radiator hose, 2nd from live data engine measuring block 1, third column instrument measuring Block 17 coolant temperature. He shows lots of Interest and curiosity about learning automotive and engine Technologies.( that's always a good sign)

all data taken in deg C

call M IR temp reading , VCDS Engine block1Temp Reading , Instrument Reading (block 17)

Engine off,
Electronics on 32 27.9 0

engine on
1 min 30.6 33.3 0
2 min 32.2 38.7 0
3 min 38 40.5 0
4 min
5 min
6 min 40,6 44.1 0
7 min 44.1 45.0 0
8 min 46.5 44.1 0
9 min 49 47.7 0
10 min 47.9 50.4 0
11 min 50 52.2 0
12 min 56 53.1 0
13 min 57 54.9 0
14 min 56.9 57.6 0

reving engine to 20k rpm, reading taken at 1 min intervals

62.6 62.1 0
68 63.9 0
73 66.6
72.4 70.2
78.2 72
77 73.8
81 75.6
80 76.5
87.9 77.4
85.2 78.3
88.9 78.3 0

the last post all the spacing and columns get messed up. So I am reposting his data collection:


all data taken in deg C IR temp reading VCDS Temp Reading Instrument Reading (block 17) Electronics on 32 27.9 0 1 min 30.6 33.3 0 2 min 32.2 38.7 0 3 min 38 40.5 0 4 min 5 min 6 min 40,6 44.1 0 7 min 44.1 45.0 0 8 min 46.5 44.1 0 9 min 49 47.7 0 10 min 47.9 50.4 0 11 min 50 52.2 0 12 min 56 53.1 0 13 min 57 54.9 0 14 min 56.9 57.6 0 reving engine to 20k rpm, reading taken at 1 min intervals 62.6 62.1 0 68 63.9 0 73 66.6 72.4 70.2 78.2 72 77 73.8 81 75.6 80 76.5 87.9 77.4 85.2 78.3 88.9 78.3 0

I have tried several different way to post the data and the spacing of text is getting messed up and becomes unreadable . at least on my browser. All his good data collection and formatting is getting mixed up. I hope you guys can read it.



all data taken in deg C

IR temp reading , VCDS Engine Block 1 Temp Reading, Instrument Reading (block 17)
Engine off,
Electronics on 32 27.9 0

Engine on:
1 min 30.6 33.3 0

2 min 32.2 38.7 0


3 min 38 40.5 0

4 min

5 min

6 min 40,6 44.1 0

7 min 44.1 45.0 0

8 min 46.5 44.1 0

9 min 49 47.7 0

10 min 47.9 50.4 0

11 min 50 52.2 0

12 min 56 53.1 0

13 min 57 54.9 0

14 min 56.9 57.6 0


reving engine to 20k rpm, reading taken at 1 min intervals, Instrument Block 17 was 0 all the time!

62.6 62.1 0

68 63.9 0
73 66.6 0
72.4 70.2
78.2 72

77 73.8 0
81 75.6
80 76.5 0
87.9 77.4 0
85.2 78.3 0
88.9 78.3 0

if you were reading coolant temp in block 17 and thru the whole process the reading is 0, bad sensor or wire?

1st thing I would do is install a new sensor onto the harness and check the reading on block 17. If the reading agrees with the block 1 reading, you know the sensor is at fault, and you can install it into the coolant manifold.

I feel like the op had made a mountain out of a moles hole...the cct is stupid cheap, a common failure and can be changed in less than an hour so long as you have fresh coolant on hand. Not being negative here as these repairs can be very intimidating and confusing. I get hot sweats just thinking about computer programming.

When you hear hooves look for horses not zebra.

The cct fails so often that from this point on any time i pull a BHW it will be replaced if i can't remember doing it before (sadly that may have been 2 weeks ago)