551 Error Code For Corbitt Tractor Models
There are 2 kind of error description.
Hand Throttle (STD cab) Idle Validation Switches are both open
Foot Throttle Idle Validation Switches are both open (engine controller pins B25, B26)
Hissing noise at expansion valve, Loss of refrigerant.Restriction in refrigerant system.Check receiver-dryer for uniformity of temperature.