CPIN responded with "sim not inserted" even when new sim card is present when at low signal strength

I use WP7609. Every 5 seconds, the microcontroller will send AT+CPIN? Command to check for sim card presence.

I found that when the signal strength is weak (around -70 to -75 db), the modem can return “Sim not inserted” within 20 to 30 minutes when idling. Take note the data SIM card is new.

After this status stays for around < 10 seconds, the modem starts to search for network.

If it possible that the status will return “sim not inserted” when the modem is initialising & prepare to search the network ?

Could this be due to EMI ?

What could be possible cause ?

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Do you have mangoh red baord?
You can try it in mangoh board and see if this is related to your hardware.

Mango red does not allow plug and play.

Anyway, the issue happens on our pcb prototype board.

does your original test relate to plug and play?
Didn’t it relate to low signal strength?

It is related to low signal strength.

then why did you say “Mango red does not allow plug and play”?
what is the relationship on testing this on mangoh red baord?

I don’t have mango red board.

then you need to get one to isolate if this is related to your hardware or SIM card or network.
From my experience with mangoh board, i never saw such issue that “+CPIN responded with “sim not inserted” during low signal strength”