If all three anti dust fans rotate, but have error then check fan rotation sensors. Look levels on F620, F621 and F622 connectors ( pin 3 ) . There should see changes, when fan stopped and when fan rotate. Hold fan ( do not allow to rotate ) and then release. You should see changes on pin 3.
If rotation sensors work, but still have error then check connectors. Rotation sensors are connected to PDC13 pin 1, 4 and 7 ( there signals from F622, F621 and F620 ) .
If all OK, but still have errors then faulty PDC20, CTL20, or some connector on them.
On Fuji 370 minilab ( LP2000 printer ) error E-2502 can cause :
Missing power supply on fan (F620/F621/F622) .
Anti-dust fan (F620/F621/F622) malfunction. Fan has power supply, but doesn't rotate.
Rotating sensor malfunction. Fan rotates, but no level changes from fan rotation sensor.
Connection error or disconnection between anti-dust fan(F620/F621/F622) and PDC13 on PDC20 circuit board
Circuit protector F4 on PDC20 circuit board trip
PDC20 circuit board malfunction
CTL20 circuit board malfunction