Hi, following a related but distinct SIM issue on the same module (EG912U-GL) that may share underlying cause with what’s reported here, posting in case it’s useful context, or please redirect me to a more appropriate thread if this isn’t the right place.
Module: EG912U-GL, firmware EG912UGLAAR03A18M08
Symptom: AT+CPIN? returns +CPIN: READY with one specific SIM (Zong, Pakistan), but returns +CME ERROR: 10 (“SIM not inserted”) with every other physical nano-SIM we’ve tested, two other Pakistani carriers and two UK IoT SIM providers — reproduced identically across two separate assembled boards.
Diagnostics:
AT+QSIMDET=1,0 / 1,1 : both accepted (OK), no change in outcome
AT+QSIMVOLT=0/1/2 : returns CME ERROR: 58 on all values, appears unsupported on this firmware
Oscilloscope capture of SIM_RST/SIM_DATA during power-up: the working SIM shows initial toggling settling into a stable high state (~3.3V, successful ATR); the failing SIM shows similar initial activity but drops to ~240–320mV and stays low, consistent with the module attempting one voltage-class recognition, failing, and powering down the interface (matches the behavior described in Quectel’s own “SIM card cannot be recognized” troubleshooting guide)
Cross-checked the same “failing” SIM on a different modem chipset (SIMCom A7670E) which registers and initializes normally there, confirming the SIM card itself isn’t defective
Question: Is there a known ATR/voltage-class negotiation limitation on this firmware build, and is there an alternate way to force SIM voltage class given AT+QSIMVOLT isn’t accepted? Does the issue is with Sim-lock for specific regions/companies?