Hey there,

I am having some trouble with my company's Hyster H60ft forklift and I am hoping someone has some input as to what is going on.

The trouble code is 51-7 and I've looked it up in the service manual and it tells me that:
"DTC 51-7 - Throttle Position Sensor Signals A and B Not At Commanded Value"

So the issue im having with this unit is that about half the time when I start the unit and go to use the throttle it has no response. Then I'll turn it off and start it again without changing anything and the throttle will respond like normal. This happens over and over again. When the throttle doesn't engage the armature that the 'driver' is supposed to pull in to activate the TPS doesn't move and can be moved manually to engage the throttle.

I have spent some time troubleshooting it and the connector on the output of the throttle is sending signal voltage as it should be (confirmed 3x) the throttle position sensor (TPS) is receiving signal voltage as it should according to the test procedure in the service manual. I checked that the fuel in the unit is diesel and not gasoline and it was indeed diesel. I took it for a good hard test drive to see if I could shake any loose wires or connections loose. I checked all the grounds that I could find in the schematics for the fuel system.

If there is any more information I can provide that would help feel free to ask

Thanks for reading