Step 1 : The EMMC must make planting-beads and wipe up the tin beads with the newspaper,and also change the VCCQ voltage in the setting;  Step 2 : If the EMMC_AUTO_8BIT can’t work,use the EMMC_AUTO_4BIT to have a try; If it can’t work by reading four areas on the left,try to read a area alone; Exchange the chip of same type to try(make sure of the chip well or not); Fly line reading EMMC mistake:  Step 3 : Make sure of the length of the flying line in 10CM; If the signal line and EMMC key port connect correctly; If the EMMC power supply is normal,it is generally 3.3V or double power of 3.3V and 1.8V; If the main chip has stopped working(power supply,clock,restoration),complete one is OK; Or remove the resistance connecting with the signal line,weld the fly line on the welding pad beside to EMMC; The EMMC chip damage itself : The reading has not finished(half or more),try more times to see if it’s the same position every time. The EMMC chip damage itself(find the mainboard with same chip); Clean away the external interference(obvious for desktop computer) : electric soldering iron on-off,light on-off,etc.