If you can get to them there are a couple solenoids you could check on the hydraulic manifold block between the power unit and the mast. The block is covered by a black shield with 4 -10mil bolts on each side (you don't have to remove them all the way.) On the right hand side of the block there are 2 solenoids stacked labeled SVT (solenoid valve tilt) and under that one. Check to make sure they are getting 24v when requested, they shouldn't ohms higher than 40ohms. Check solenoid SPA as well on the left side of that black 24v no more than 30ohms. Code 731 refers to tilt not functioning. Check the tilt sensor on the right side tilt cylinder on the power unit is functioning and not stuck.