Actually ,you could run a quick and simple test beforehand without disassembly. At least it works on the X1. Not sure about the P1. Unplug the filament PTFE going to the extruder, manually insert a piece of filament, heat up the nozzle to the last filaments extrusion temp, and then extrude 10mm. If the extruder slips on the filament, which you can feel on the filament while observing that the wheel on the extruder is turning, you should look insides the extruder. If it does not, go for the nozzle cold pull or (temporary) nozzle replacement first.
If you first check the extruder, any likely issues should be pretty obvious by discoloration in the extruder teeth and manual operation.