Identify problem of I2C

Projects Networking, Protocols, and Devices
1

After my previous problem, I bought a new I2C and LCD (1602). At first, I've tested I2C through I2C address scanner (Arduino UNO R3). No I2C found. I used MEGA and found at 0X27.
I think: 1)Pull up! 2)damaged A4 and A5!
for pull up, I connected a 5k Ohm resistance (from rear and middle pin of potentiometer) between SDA and VDD and another between SCL and VDD, no thing was detected!
for test of A4 and A5, I had no idea but measuring resistance between these two pins (11k Ohm).

Please suggest any solution.

2

The Mega2560 has on-board pull-up resistors, so that might explain part of the difference.

Post a wiring diagram of your setup!

For pull-up use a 4k7 resistor and don't use potentiometers (the risk of producing a short is to high).