As I said I think you may need a 68K pull up resistor, not 41K. What voltage does your sensor operate at, and what voltage are you connecting the pull up resistors to?
There is only a single ground connection on an EV3 sensor port. The NXT had two ground pins Pin 2 and Pin3. However on the EV3 Pin2 is used as part of the sensor type detection process. You can see that Pin 2 is not connected to ground in the schematics available from here:
http://botbench.com/blog/2014/02/19/ev3 ... available/
You can see the rules for the automatic detection logic here:
https://sourceforge.net/p/lejos/ev3sdca ... d_analog.c
as you can see from:
https://sourceforge.net/p/lejos/ev3sdca ... log.c#l129
to be identified as an i2c sensor pin 2 needs to be pulled low and pins 5 and 6 both need to be high (hence one reason for needing the pull up resistors).
There is no NXC for the EV3. However you may be able to use the dexter blocks with the standard Lego software. Please see:
http://www.dexterindustries.com/howto/c ... 3-arduino/
Please note that all of the above information is publicly available, you just need to dig a little for it...