M66 modem shuts down when 4G sim card is used


             I  have a pcb board with M66 R1.0  modem , when i use a 2G sim card  , the Modem can detect the sim card , its IMSI etc is  retrieved  through  AT  commands , but when i put a 4g sim card on it , modem automatically powers off within 1 or 2 minutes of powering on , when 4g sim card is removed and  a power on signal is applied again the Modem will stay on and answer AT commands, it answers all networks related commands like AT+COPS etc , i have tried putting the  4g sim in a 2g phone , making a call through it and then  putting it back in the board with no success .

i tried 2 different 4G sim card from Vodafone idea, and one from Reliance JIO.

ATI command to modem .
Revision: M66FAR01A12BT

I’m sorry to reply you so late.
If your problem still exists, please contact us. You need to grab the log for us to analyze.Thanks.

What??? M66 is only 2G module.

HI ,

M66 is 2G module only and it can work with companies supporting 2G network such as Vodafone , airtel but it cant work with 4G only network such as reliance Jio who doesn’t have any 2G fallback .

M66 works with 4G sim card , in 2G mode if network has support for 2G , this problem is solved ,
higher value capacitor was required on Modem Power Pin , M66 apparently requires more capacitance on Power Pin ( > 470 uF) compared to similar modems from other vendors .