If you experience a "50.2" fuser error while using a LaserJet 4000, 4050, or 4100 fuser, you should check to see if two tabs on the fuser have come loose. (They can get dislodged during shipping or during istallation.)
Turn your printer off and remove your fuser. Flip it to the gear side (the left side) and press inwards on the fuser tab to make sure it is fully clicked in place, as shown below.
Then flip the fuser over to the right side (the non-gear side) and press in on the other fuser tab to make sure it is also fully clicked in place.
(right side of a LaserJet 4000/4050 fuser pictured below)
(right side of a LaserJet 4100 fuser pictured below)
