59.99 error sounds like sensor issues, but it is not. It is caused by the drop of power supply voltages. Following are what I did to fix this problem.
1) Checked the out put voltage from the power supply while powering up. The orange wire(the thicker one) and the yellow wire (the thinner one) should be at least +3.5v. This voltage is for all the senor and logic signals. If it is lower than +3.3v, it will cause error codes. HP uses a group of long and thin wires for the sensors and motors, there are voltage drops on those wires. By the time the senor signals reached the main board, the drops are low enough to cause error. It is will happen when the power supply aged and providing weak/less power/voltages. Mine was fluctuated around +3.3v
2) Checked and replace the two lage caps on the power supply.
3) Adjusted the +3.3v up to +3.55V. If you are facing the power supply on the of display panel side, the adjustment pot is the orange one on the upper right corner of the power supply. The white glue on the pot must be removed before adjusting.
4) Adjusted the +24V output power too, to ensure motors have proper power. The multiple red thin wires carry +24V. The adjustment orange pot is the one closer to you.
5) Restart , no more error code. Ready.
Hope it will help.
Feng