BG95x0A-GL: CME Error: 31

IoT Modules LPWA Module
1

When sending the AT command AT+CGATT?, I sometimes receive the response:

+CME ERROR: 31

According to Quectel_BG77xA-GL & BG95xA-GL AT Commands Manual v1.1, error code 31 means “Network timeout.”

What is the correct way to handle this error?

  • Is this a transient condition that should be handled by retrying the command?
  • Should the device wait and retry later?
  • Under what circumstances, if any, is a modem restart recommended?

I would like to understand the expected behavior of the BG950A-GL when this error occurs and the best practice for handling it in production firmware.

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2

pls run the AT

AT+QENG=“servingcell”

Perhaps the modem has completely entered the OOS state.

3

After receiving +CME ERROR: 31, I run the command AT+QENG="servingcell" and receive the following output:

... Other AT commands
08:41:20:291 -> DBG (UART NB 200): REQ: AT+CFUN=1
08:41:20:307 -> DBG (NB CONN 1117): RES: OK
08:41:20:365 -> DBG (CHATSCRIPT 89): 16 -> 17
08:41:20:365 -> DBG (NB CONN 802): Modem state: CONFIG
08:41:20:365 -> DBG (UART NB 200): REQ: AT+COPS?
08:41:20:365 -> DBG (NB CONN 1117): RES: +CEREG: 2
08:41:20:365 -> DBG (CHATSCRIPT 89): 17 -> 18
08:41:20:365 -> DBG (NB CONN 802): Modem state: CONFIG
08:41:20:365 -> DBG (UART NB 200): REQ: AT+COPS=0
08:41:20:365 -> DBG (NB CONN 1117): RES: +COPS: 0
08:41:20:400 -> DBG (NB CONN 1117): RES: OK
08:41:20:400 -> DBG (CHATSCRIPT 89): 18 -> 19
08:41:20:400 -> DBG (NB CONN 802): Modem state: CONFIG
08:41:20:400 -> DBG (UART NB 200): REQ: AT+CGATT?
08:41:36:831 -> DBG (NB CONN 1117): RES: +CME ERROR: 31
08:41:36:831 -> ERR (NB CONN 1088): Network timeout
08:41:36:831 -> DBG (UART NB 200): REQ: AT+QENG="servingcell"
08:41:36:831 -> DBG (NB CONN 1117): RES: +CEREG: 0
08:41:36:831 -> DBG (NB CONN 1117): RES: +CEREG: 2
08:41:36:874 -> DBG (NB CONN 1117): RES: +CEREG: 2
08:41:36:874 -> DBG (NB CONN 1117): RES: +CEREG: 0
08:41:36:874 -> DBG (NB CONN 1117): RES: +CEREG: 2
08:41:36:874 -> DBG (NB CONN 1117): RES: +CEREG: 0
08:41:36:960 -> DBG (NB CONN 1117): RES: +CEREG: 0
08:41:36:960 -> DBG (NB CONN 1117): RES: +QENG: "servingcell","SEARCH"
08:41:36:960 -> DBG (NB CONN 1117): RES: OK
08:41:36:960 -> DBG (CHATSCRIPT 89): 19 -> 20
08:41:36:960 -> DBG (NB CONN 808): Modem state: ATTACH
08:41:36:960 -> DBG (UART NB 200): REQ: AT+CGATT?
08:41:36:960 -> DBG (NB CONN 1117): RES: +CGATT: 0
08:41:36:960 -> DBG (NB CONN 1117): RES: OK
4

It might be that the modem has just started up and initialized.

5

Yes, it has just started up, but what is the recommended procedure when receiving this type of error? Should the modem simply be restarted, or is there a preferred handling method?

6

No, I suggest you use AT+CEREG or AT+QENG=“servingcell” to check the registration network status.