Thanks for the response.
The type of printer I have is an Ultimaker 2 Extended.
So not sure if I have the green coloured screw terminal you mentioned.
Couldn't seem to find it.
Also, I do believe that I have the PT100 thermistors.
I did check the connections, both at the PCB side and at the heated bed so far, to see if they were loose.
Today, I turned on the machine and I didn't get an error immediately.
With TMP03 and TMP01 switched, I did not get an error, even after about 5 mins.
I swapped them back and did not get an error immediately, but after about 6 mins I got the ER02 error.
I loosened the screws at the heat bed sensor location, maybe I over tightened it when I was checking for that problem. Now its up to over 45 mins with no error.
Should I attempt heating the bed again?