How to test SIM registration and status?

What are good commands for testing SIM card status and registration issues?

Today, I was experimenting with how to recognize SIM card problems. I took 3 cards that are known to be bad when tested in other hardware, and expected to find some clear results. I didn’t, but I think I just need some guidance for what commands to be using.

The command that made the most sense was:


I received 3 different responses:

  • 0,3
  • 2,1
  • 2,4

The first is “denied” which is fairly straightforward. The 2nd suggested it is successfully registered, but it would not provide an IP address and didn’t actually function. The 3rd behaved like the 2nd, but had the “4” suggesting “other” for a registration status. They also showed servingcell info, and +QNWINFO information even though I thought they shouldn’t.

What other commands are helpful for tracking or understanding card issues. I want to be able to find when there is a card problem so I know when to replace a card and when to troubleshoot modem issues / configurations.

Thank you, Chris

Dear Uberdome,
Thanks for your inquiry in Quectel forum.
About your issue, it is better to use AT+CREG? and AT+CEREG? to check it.

Normally, we just need to care about the second parameter of the return value, the following is the explanation about the return value. Only the second parameters return 1 or 3, it just can said that the module already register on local network or roaming network. Thanks!

Testing further, I found these results on 2x of the cards:

+CEREG: 2,4

+CREG: 2,1,"1B52","7DAC58D",2

This looks like they are only connecting to 3G connections. They are configured, however, to only search LTE connections here:


What sort of behavior gives the result “unknown” for registration status?

Thank you, Chris

Dear Chris,
Could you help to provide more information to us, then we can help confirm the issue. Thanks!
Have you change another SIM card to have a try ? If you do not fix NWSCANMODE to LTE only, whether it is still have such results ? And how about the LTE network signal, could you double check it ? Thanks!

According to ATI, I have BC66NBR01A10. And it makes answer for command AT+CREG? +CREG: 0,5.
But in manual Quectel_BC66BC66-NA_AT_Commands_Manual_V2.2.pdf is no such command. Where this command is described for my device?

If you are using BC66, you are advised to use “AT+CEREG” to check the registered network status.
You can also perform the following commands to check network or signal conditions: