nRF9151-DK (HW Rev 1.4.0) — SIM completely undetectable on two boards, all diagnostics exhausted

Question

Hardware & Firmware Board: nRF9151-DK (DKA), two separate units, both sourced from Farnell/Mouser DK Hardware Revision: 1.4.0 DK PCB version: v0.2.0 (from Board Configurator log) Board Controller FW: 1.2.1 Modem firmware: mfw_nrf91x1_2.0.4 TF-M: v2.1.1-ncs4 AT%HWVERSION : nRF9151 LACA A1A nRF Connect for Desktop: latest available at time of testing Application tested: stock AT Client sample ( nrf/samples/nrf9x/at_client ) Problem Description Both nRF9151-DK boards are completely unable to detect or communicate with any SIM card. The symptom is identical on both boards. Two different nano-SIM cards were tested. Previous nRF9151-DK boards sourced from a different supplier worked without issue. The modem AT interface itself is healthy — AT+CGMR , AT%HWVERSION , AT+CFUN , and IMEI retrieval (confirmed via nRF Quick Start) all function correctly. Only SIM-related commands fail. Board Configurator State SIM Option: SIM Card selected (not eSIM) Write config applied, board power cycled sim-select pin (pin 14): ON Board Controller FW: 1.2.1 Full AT Command History — Session 1 (initial diagnostics) AT+CFUN? +CFUN: 0 OK AT+CIMI ERROR AT+CFUN=1 OK AT+CFUN? +CFUN: 1 OK AT+CIMI ERROR AT%UICC? ERROR AT%XICCID ERROR AT+CRSM=176,28589,0,0,10 ERROR AT+CGMR mfw_nrf91x1_2.0.4 OK AT%HWVERSION %HWVERSION: nRF9151 LACA A1A OK Full AT Command History — Session 2 (following Nordic AI assistant advice) AT+CFUN? +CFUN: 0 OK AT+CFUN=1 OK AT+CIMI ERROR AT+CFUN=0 OK AT%XFACTORYRESET=0 OK AT+CIMI ERROR AT+CFUN? +CFUN: 0 OK AT+CFUN=1 OK AT+CIMI ERROR AT+CFUN=0 OK AT%CSUS=0 OK AT+CFUN=1 OK AT+CIMI ERROR AT+CFUN=0 OK AT%CSUS? %CSUS: 0 OK AT+CFUN=0 OK AT%XSIM=1 OK AT+CFUN=1 OK %XSIM: 0,9 Key Diagnostic Findings AT+CIMI returns plain ERROR in both CFUN=0 and CFUN=1 — not +CME ERROR: 10 (no SIM) or +CME ERROR: 13 (SIM failure). This pattern persists across two boards and two different SIM cards. AT%UICC? returns ERROR — the SIM interface software-switching command is not functioning or not applicable on this hardware variant. AT%XFACTORYRESET=0 did not resolve the issue — modem NVM configuration is not the cause. AT%CSUS=0 explicitly selects the external SIM interface. Even after applying this in CFUN=0 and then switching to CFUN=1 , AT+CIMI still returns ERROR . %XSIM: 0,9 — after enabling SIM state notifications with AT%XSIM=1 and entering CFUN=1 , the modem unsolicited response reports SIM state 0 (not ready) with cause code 9. This confirms the modem is actively attempting to initialize the SIM interface but failing at the hardware communication level. AT+CRSM=176,28589,0,0,10 returns ERROR — direct SIM filesystem access is impossible. nRF Quick Start Verify passes — Manufacturer, Hardware version, and IMEI are all read correctly, confirming the modem itself is functional. Custom Application Boot Output (for reference) [00:00:00.289] hall_pickup: Bringing LTE interface up... [00:00:00.546] nrf_modem_lib_trace: Trace thread ready [00:00:00.662] hall_pickup: Waiting for LTE connection... +CEREG: 90 [00:00:00.906] nrf_modem_lib_netif: The modem reports a UICC failure. Is SIM installed? What Has Been Ruled Out Faulty SIM card — two different SIM cards tested on both boards, all fail identically Application firmware interference — AT Client sample used in clean state Modem NVM configuration — AT%XFACTORYRESET=0 performed, no change Incorrect SIM interface selection — AT%CSUS=0 explicitly applied, no change Modem AT interface fault — standard modem queries ( AT+CGMR , AT%HWVERSION , IMEI) all respond correctly Board Configurator not applied — Write config applied, board power cycled Questions What does %XSIM: 0,9 specifically indicate? What is cause code 9 in the context of %XSIM on mfw_nrf91x1_2.0.4 ? What does the LACA variant code in AT%HWVERSION: nRF9151 LACA A1A indicate regarding the SIM interface? Does this variant have a functioning external nano-SIM interface, or does it differ from previously available variants? Why does AT%UICC? return plain ERROR on mfw_nrf91x1_2.0.4 with this hardware variant? Is AT%UICC unsupported on nRF9151 LACA A1A ? Is Board Controller FW 1.2.1 on DK Hardware Revision 1.4.0 (DK v0.2.0) fully compatible with SIM mux switching via the Board Configurator? Could an outdated Board Controller FW cause the sim-select signal to not switch correctly despite Write config being applied? Is there a known issue with nRF9151-DK boards at Hardware Revision 1.4.0 or DK v0.2.0 related to SIM card detection? Both affected boards share the same supplier batch (Farnell). Is there a known batch or revision difference compared to boards from other distributors that would affect SIM functionality?