Daniel,

Complete the CANBUS circuit test first. The steer column has a rubber cover on the right side. Under the cover is a test port computer connection. The two top sockets are A and B. The bottom one is C. A ad B should read about 2.5 volts with key switch on and using C as the ground. The voltage can vary between the two 1 to 1.5 volts. As long as it is close to 4.5 volts your good. If you read nothing, try a different ground. If it reads now, bad ground. With battery disconnected, VOM set on ohms, check resistance between pins A and B. Should read about 60 ohms. If you read 120, bad termination resistor. If you have the Kubota 3.8, check wires from ACU to VSM. The ACU is a module mounted on the left side that helps the ECU talk to the VSM. The 155's were also known to have a failed left side harness. With everything connected and switch on, move the harness up and down. Watch the display and see if code changes. Good Luck.