Pioneer YN020GMFI22M2D Service Manual page 54

8.4.2.5 E5 (Over-voltage or under-voltage protection) diagnosis and solution.
Error Code
Malfunction decision
conditions
Supposed causes
Trouble shooting:
E5
An abnormal voltage rise or drop is detected by checking the
specified voltage detection circuit.
● Power supply problems.
● System leakage or block
● PCB faulty