Modem & SIM annotated diagnostic test

Run modem and SIM annotated AT diagnostic tests

Use a serial terminal to connect to your modem and run each command. Record the outputs for support.

Note: Some scans (e.g., network search) can take up to 3 minutes to complete.

Command	Function	Sample response
AT	Attention; verifies command path	OK
ATI	Module number	SARA-U201-03B-00
AT+CGMI	Manufacturer identity	u-blox
AT+CGMM	Manufacturer model identity	SARA-U201
AT+CPIN?	SIM PIN state (Hologram SIMs do not require a PIN)	+CPIN: READY
AT+CCID	SIM ICCID (profile identifier)	+CCID: 891234…
AT+CRSM=176,28539,0,0,12	Read FPLMN (forbidden networks)	+CRSM: 144,0,“FFFFFFFFFFFFFFFFFFFFFFFF”
AT+CFUN?	Module functionality	+CFUN: 1,0
AT+CSQ	Signal quality	+CSQ: 22,4
AT+CREG?	GSM/SMS registration	+CREG: 0,5
AT+CGREG?	3G registration	+CGREG: 0,5
AT+CEREG?	LTE/EPS registration	+CEREG: 2,5,“MI9S”,“25SS404”,8
AT+CGDCONT?	PDP context parameters (APN)	+CGDCONT: 1,“IP”,“hologram”,“0.0.0.0”,0,0
AT+CGACT?	PDP context activation	+CGACT: 1,1
AT+COPS?	Operator selection status	+COPS: 1,2,“310260”,2
AT+COPS=?	Networks in reach (scan)	+COPS: (1,“AT&T”,“AT&T”,“310410”,2)

Note: Prefer capturing raw terminal text output instead of screenshots.

If AT+CSQ is very low, relocate the device or improve the antenna.
If not registered (+CREG/+CGREG/+CEREG), verify SIM activation and supported RAT/bands.
Ensure APN is set to hologram and the active PDP context matches the APN line.