All Baseline and some Mid-Range PIC microcontrollers require a special –ICD device mounted on a debug header circuit board to enable the debugging feature. For a list of these devices and the required ICD header board part number, see the “Processor Extension Pak and Header Specification” (DS50001292).
Each ICD header board comes with the necessary – ICD device and is used on the target board instead of the production microcontroller. However, most header boards have an RJ-11 debug connector which requires the AC164110 RJ-11 to ICSP™ adapter kit to connect it to MPLAB PICkit 4.
Many Mid-Range PIC microcontrollers and all PIC18 and 16-bit PIC microcontroller devices do not require an ICD header and can be debugged directly through the ICSP programming connections.