M66 module doesn't restart


my M66 module sometime falls into state, where I can’t restart it from.

After 10 x sending AT to M66 without response, I try to restart module - see picture
Pull PWRKEY pin for 870ms down, then wait 13 sec and try to switch on.

However VDDEXT voltage doesn’t change, no NORMAL POWERDOWN on serial line appears.

Communication with modem is stuck, and only way how to fix is power down / power up.

However netlight pin stil shows that modem is attached to GSM network.
Any idea?

Many thanks

Dear Radomir Kozub,
Thanks for your inquiry in Quectel forum.
You mean you cannnot restart the module with PWRKEY pin ? Could you double check the following Timing of resetting system? Normally, you should make sure it have the 500ms delay before resetting the module. And you also can try to use AT+CFUN=1,1 to reset the module. Thanks!