Adjust the engine idle speed periodically on the engine at normal operating temperature.
To adjust the idle speed:

Engine oil and filter change
Throtile cable playPrecautions
Precautions for exhaust system
To avoid
the risk of being burned, do not touch the exhaust system when the
system is hot. Any
service on the exhaust system should be performed when the system is
cool.
Caution
make sure that the exhaust pipes and muffler ...
DTC “c28” (p1655): secondary throttle
valve actuator (stva) malfunction
Detected condition and possible cause
Detected condition
Possible cause
The operation voltage does not reach the stva.
Ecm does not receive communication signal from the
stva. Stva can not operate properly or its motor locked
Stva malfunction.
...
Turn signal / side-stand relay removal and
installation
Removal
Turn the ignition switch off.
Remove the frame cover assembly. Refer to “exterior parts removal and
installation” in section 9d .
Remove the turn signal/side-stand relay (1).
Installation
Install the turn signal/side-stand relay in the reverse
order of removal ...