Arduino mega problem

Im not sure if this post belongs here so forgive me.

i have been scratching my head trying to get a sketch that works perfectly on an arduino nano work on the arduino mega but when i upload it to the arduino mega not all the functions from the sketch work.

is there any reason the mega would read data differently than the nano?.

or is it just faulty ?.

Post your code, and describe what behavior is different, and we can probably tell you what's different

Without any details, I can only mention the obvious being that the pinouts are different. i2c (SDA and SCL) for example is on A4 and A5 on the Nano.

On the Mega, it would be 20, and 21.