Y motor keeps moving then Error 0031? (Page 2 of 2)

This machine uses photo sensors on all of it's axis as you said. However they do not react to magnets. That would be a hall sensor. What happens in this machine is that the photo sensor is a U shaped device. On one side is and IR LED. On the other is a photo transistor. As long as the beam of light (IR so it's invisible) is allowed to shine across the device to the photo transistor it will conduct current through the transistor like a switch that is on. If the beam of light is broken such as is the case in our machines by a plastic part that slides into the U shape then the photo transistor stops conducting like a switch that has been turned off. Now depending on the type of devices our machines have they could do the reverse and conduct when blocked and not conduct when unblocked.

However there are no hall sensors (they react to magnets) in our machines and thus no magnets either.

What it sounds like to me is that the left side of the Y carriage is hitting the back of the machine before the right side where the sensor and home is. So it sits there skipping and eventually times out and throws up the error code. I would suggest for the op to do what the previous poster said. Pull the carriage all the way forward and see if both sides hit the X pulley on each side at the same time. If not then forcefully pull the side not meeting the pulley to force it to skip a notch or two on the belt. You can do same thing by pushing it all the way back on both sides till it won't move further. Again with force as you want to make it jump a notch or two on the gear. Depending on how far it has skipped. I had to do this on mine once as it was trying to home and got stuck on a plate that was set too high. Made the left side of the Y carriage skip a few notches.