6871er1003c how much for the main part

There is no schematic as such because if the boards fail, under warranty, they are replaced.
Gone are the days of engineers. They use fitters now.

• Code: L4 01
• Description:Main motor lock detection. The main motor does not rotate. After rotation of the main motor, the motor lock signal is detected for 1 sec or more. During rotation of the main motor, the motor lock signal is detected for 1 sec. When the main motor is stopped, the motor lock signal is not detected for 5sec or more. (Though the motor is stationary, it is judged as stable rotation.)
• Causes:Main motor unit abnormality Improper connection or disconnection the main motor and the harness. MCU PWB abnormality
• Remedy:Use SIM 25-01 to check the main motor operations. Check connection of the main motor harness/connector. Replace the main motor. Replace the MCU PWB.

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Have you tried eBay for the parts?

Might be "tE" error code. Thermistor error. A $6 parts and pretty common and causes the symptoms you described.

Your going have to open it up. I think its the PWB ASSY, MAIN Part#6871ER1003C. Unscrew the top on the back and from the front push the top back. That will slide it back, it you see a red light on the power assembly then its not your problem but if its off then that is the part to replace. I'm ordering the part right now. Its pretty easy to unplug all the cables. I found it from 53 to 160 on the internets. You just have to shop around and call them to see if they actually have it in stock. http://media.fotki.com/1_p,ssbrgfbfrktqtddxgtqsskgwtqkq,vi/rwsbqgrbwxrqrkswwdq/1/1303472/5961857/image1927948615726646899img-or.jpg

It sounds like you have a hall sensor failure, if your machine fills with water and then does the buzz thing without the drum ever moving in the cycle.
The Hall sensor (part number 6501KW2001A) has failed. The hall sensor is rather easy to replace, and is covered by a seven year part warranty (in the US). Take the back cover off. Take the big nut off and remove the motor rotor. Remove the bolts holding the motor windings. Remove the electric plug on the sensor and unclip it from the motor winding. Snap new sensor on and reassemble. Usually takes under a half hour. On a difficulty scale of 1 - 10, it might rate a 4. This should be a Fix-Ya for your machine, and at basically no cost!
In the US, find a service provider using your zip code at http://us.lgservice.com/index_b2c.jsp or call LG at 800-243-0000

sorry to say it but i think you still have a faulty hall sensor.
Try another one and send the last one back as being faulty.
It means the motor gets the power but the hall sensor stops it dead in its track