Daikin GYEQ20AN Service Manual page 176

Flow Charts for Troubleshooting
Inter-CPU Communication Failure/
41
Software Mismatch/Abnormal ROM
Sub-code 0: Unable to communicate between I/O CPUs for 20 seconds.
Description Sub-code 2: Unable to communicate between ignition CPUs for 20 seconds.
of the failure
Sub-code 3: Abnormal I/O CPU ROM
Sub-code 5: Abnormal ignition CPU ROM
CPU program write error; power supply circuit board failure; main circuit board failure; T phase missing
Possible
causes
of the failure
Flow chart
If sub-code 0
Software rewritten?
YES
Rewrite software
again
165
If checker display is
If sub-code 2
NO Replace main
circuit board
NO
Harness
inspection
Is the power
NO
supply circuit
board LED1 lit?
YES
Is the power supply
circuit board fuse F4
Is the harness for main
operating normally?
circuit board CN10 and power
supply circuit board CN107
operating normally?
YES
Replace main
voltage normal?
circuit board
SiAUY361411EA
Error
code
If sub-code 3 or 5
Replace main
circuit board
NO
YES
Replace the
fuse(s)
Is the supply NO
YES
Power supply
voltage inspection
Replace the
circuit board
025909-00EN02
Troubleshooting
U2