New Holland T8010 Manual page 1640

Section 55 - Electrical System, Controller - Chapter 5
FAULT CODE ARM 10091
Controller Internal Failure
Cause:
Controller internal failure: +5 V or +8 V regulator is out of range.
Solution:
Make sure the controller has a good connection (C137) to the battery and is properly grounded.
Shut down the tractor and restart. Calibrate the armrest controller. If the same fault code appears again, replace
the controller.
NOTE: See schematic sections 47 and 48 on schematic poster.
55-5-35