Hint:
Past problems that seem unrelated may also help in some cases.

Operation flow
Symptom confirmation and diagnostic trouble codeDiagnosis system
Description
Air conditioning system data and the diagnostic
trouble codes (dtcs) can be read through the
data link connector 3 (dlc3) of the vehicle. When
the system seems to be malfunctioning, use the
intelligent tester to check for malfunctions and
perform troubleshooting.
...
Ig power source circuit
Description
This is the main power source supplied to the air conditioning amplifier when
the ignition switch is on.
This power source is used for operating components, such as the air conditioning
amplifier and servo
motors.
Wiring diagram
Inspection procedure
Inspect fuse (ecu-i ...
Removal
Disconnect cable from negative battery terminal
Caution:
Wait at least 90 seconds after disconnecting the
cable from the negative (-) battery terminal to
prevent airbag and seat belt pretensioner activation.
Remove mass air flow meter
Disconnect the mass air flow meter connector.
...