pto won't engage on john deere 155c?

Sounds like a micro switch issue shutting the engine down, check all the safety micro switches are depressing correctly,and the wires have not come loose on them, seat switch/deck engagement switch, if it thinks you are trying to engage the clutch whilst not in the seat or the grass collector is not fitted properly it will shut the engine down.

Husqvarna man
March 2010