I have been attempting to extract the firmware from an HVAC controller board using my Pickit3 and MPLAB X.

It seems that many HVAC controllers are PIC based and most are kind enough to include debug/flash pins. Grabbing the firmware images should be trivial once the correct pins are traced out. MPLAB X will see my Pickit3 and the target MCU, but it fails to pull an image that isn’t all zeros. (The “bin” file is a text file with each line noting the start address, followed by 16 byte values.)

I do get an occasional “Target device ID invalid message” but that is usually due to my janky wiring to the board. Once I get that issue cleared, MPLAB will always warn that the debug bit (byte?) is set on the MCU. (That doesn’t make sense as the MCU should be running standalone on the board during normal operation.)

Is there some kind of read protection that may be enabled on the PIC? Do I just need to unsolder the PIC and put it in its own dedicated circuit for pulling the firmware?