Most of the time, the BC660K can finish network registration within 10 seconds. However, the BC660K may hold at network registration for longer than 5 minutes without complete. By inspecting the AT command traffic, I found that the BC660K had reported a registration failure with EMM reject cause #19.
Referring to 3GPP TS 24.008 Annex G,
Cause #19 – ESM failure
This EMM cause is sent to the UE when there is a failure in the ESM message contained in the EMM message.
Why the BC660K may occasionally report ESM failure and what are the possible causes for the failure?
Below is my BC660K AT command traffic while waiting for network registration and see the ESM failure.
[2023-09-07 15:18:29.962] TX:AT+CFUN?
[2023-09-07 15:18:29.978] RX:+CFUN: 1
[2023-09-07 15:18:29.978] RX:OK
[2023-09-07 15:18:30.250] RX:+CPIN: READY
[2023-09-07 15:18:30.250] RX:+CEREG: 2
[2023-09-07 15:18:30.378] TX:AT+CGATT?
[2023-09-07 15:18:30.378] RX:+CGATT: 0
[2023-09-07 15:18:30.378] RX:OK
[2023-09-07 15:18:31.385] TX:AT+CGATT?
[2023-09-07 15:18:31.385] RX:+CGATT: 0
[2023-09-07 15:18:31.385] RX:OK
…
[2023-09-07 15:18:52.765] TX:AT+CGATT?
[2023-09-07 15:18:52.781] RX:+CGATT: 0
[2023-09-07 15:18:52.781] RX:OK
[2023-09-07 15:18:53.772] TX:AT+CGATT?
[2023-09-07 15:18:53.772] RX:+CEREG: 3,“XXXX”,“XXXXXXXX”,9,0,19
[2023-09-07 15:18:53.793] RX:+CEREG: 2
[2023-09-07 15:18:53.793] RX:+CGATT: 0
[2023-09-07 15:18:53.793] RX:OK
Thank you for your kind attention.