The troubleshooting steps listed for this code said to check the park lock circuit fuse. If the fuse was good to check relay #5 the park lock relay. There wasn't anymore than that, and none of that would fix my problem.
The relay wasn't working so I swapped it with the work light relay to see if the problem went away. The problem did go away with the relay change, so problem solved, or so I thought. The tractor ran okay for a while and then the park locked again.
Swapped the relays around again an it didn't work. Park is on until power is supplied to solenoid valve and no power was getting to the solenoid. This tractor has a backup brake system that will engage the park lock if the brake pedals go to the floor. I had to lift the cab to check the wiring. I checked the wiring to the brake pedal switches carefully because they run near the exhaust but found no problem with these wires.
I went back up into the cab and jumped the wires across the relay and got power back to the solenoid. I decided to check the current going to the solenoid. Wow! off the scale at 21 Amps.
Well there's your problem!
Swapped the bad park solenoid with the working MFD solenoid and measured the current again. Now it is back to normal. This tractor was recently purchased at an auction. This must have been a problem for a while because I noticed many parts had been changed like the transmission controller. It was a used controller with software for another model that had front suspension which this tractor did not have. I loaded the correct version while I was there.
This tractor has a severe engine miss and a loud noise coming from the front of the transmission. I think it is probably headed back to the auction yard for the next wide eyed buyer. I wonder if I will see it again.