Canon C2050 Service Handbook page 288

ERROR CODE
E540
Main cause The bins shift motor (M1) fails to rotate.
Condition of
detection
After the motor drive signal has been generated, the operation does not end
within a period 4 times a specific period or less:
Period: 20000 msec during initialization
The clock signal from the bin shift motor clock sensor (PI1) is absent for
250 msec or more.
The input signal from the lead cam HP sensor (PI2) does not change for
200 msec.
E-24
2000 msec during non-initialization