The modem restarts after sending the command AT+CFUN=1

[Yury Morgunov]

Hi, 

When running the at_client example, I send the AT+CFUN=1 command via the LTE link monitor. After a few seconds, the nrf9160 reboots.

I want to say that before my program worked and connected to the server. However, now I cannot even work through at_client. Commands like AT+CGMR work

If I pull out the sim card, the nrf9160 will not restart. What could be the problem?

P.S. I tried to get modem trace but tace collecor is not accepting anything. Are there any other ways to debug this problem?

Modem firmware version - mfw_nrf9160_1.1.0
I use nRF Connect SDK v1.3.0

[Yury Morgunov]

I got an oscilloscope and this is what I found on the 5V line

When I turn on the power, there is a strong voltage drop.
Strange but I tried different usb wires and used different usb power supplies. Only an external power supply of 5 volts helped. Even with an external power supply connected, the voltage briefly drops to 4V. In general, the reason is clear, now I will understand why the voltage drops so much

Many thanks for the help

[Martin Lesund]

OK,
I just saw you last response.

Just let me know if anything else is unclear.

Best regards,
Martin L.