if i'm not mistaken the round circle means the coolant level is low.
Is there a sensor in the coolant resivoir or on the side of the radiator on this unit? On the cats it means low coolant.

and the p22 code is something in the directional control
on the cat trucks it can also be triggered if the PDS (presence detection system) is triggered with the seat switch open.
check the seat switch circuit.

one other thing to consider too is if these trucks have the same relay box's like the cats do it could be a faulty relay or relay box.

on the cats we had a myriad of issues that were traced back to the bad relays or box's.

just some thoughts to throw at cha :o)

good luck