The F51 fault code on these types of washers indicates that the machine control board detects an RPS (Rotor Position Sensor) failure. This sensor is on the motor at the bottom of the washer. Here is the troubleshooting for the F51 fault code:
Do not overload the washer. Overloading can cause this fault code.
Check underneath the washer for any clothes or toys that could be under the washer and obstructing the motor from turning freely. This can occur because there is not a cover on the bottom of the Washer.
Using too little water by choosing the wrong cycle for the type of load being washed can cause this fault code.
Make sure that your drain hose is properly installed per your installation instructions. Siphoning of fill water out of the washer can cause tub resistance and will result in this fault code.
Lift the lid and reach in and make sure that the basket turns freely. If not, you could have garments stuck between the two baskets or a problem with the basket hub. Any abnormal resistance to tub movement can cause this fault.
Unplug the washer. Make sure that both the Control Board Connectors P5 (Motor Wires, red, blue and yellow), and the P10 (RPM Sensor Wires, 7 brown wires) are securely plugged into the Control Board. I have included a set of illustrated instructions (See below). These should step you through the process of teardown and component testing.
Remove the (P5) Motor Connector from the Control Board and take a resistance reading between the 3 combinations of motor wires (red/blue, red/yellow and blue/yellow). It should read around 32 ohms on the Motor Windings between any of the 3 pins on the harness. NOTE: If you do not get the proper resistance reading on the motor harness at the board, check the reading at the motor end. If you get a good reading replace the upper or Lower Harness whichever is defective. If the reading is still bad when checked directly off of the motor, then you will need to replace the motor. (See notes below for motor access.)
Unplug the P10 connector and take a resistance reading between the two outside pins (1 and 7). It should read between 600 and 21.6K ohms. *NOTE: (If it reads open you will need to pull the Rotor and Stator so you can check it right at the RPS Sensor. If it reads good at the sensor, replace the Lower, or Upper Harness whichever is open).
To access the motor and RPS sensor, lean the washer back against the wall. Secure the washer with blocks if needed. Remove the rotor (1-bolt), and the stator (4-bolts). When you pull the rotor off, check to make sure that the thin plastic beads that run between each magnet on the rotor is intact and in place. This could cause an F51 code as it will no longer separate the poles of the magnet for the sensor to read them properly.
Check the wiring connections on the motor and the RPS sensor. Unplug and then plug the wiring harness connections back in on these components 5 or 6 times. This will normally scrape through any possible corrosion or deposits on the connections. Tug slightly on the connections when they are inserted for the final time to make sure that they are secure.
Reassemble the washer and run a test load to see if the F51 still occurs.
If you need further assistance, please reply below with the checks you have made. I will be looking forward to helping you again in the near future.
You can have it repaired at your home by a Sears technician. Here is a link for the website:
Sears Home Services
I hope this helps.