# Is my Sierra Wireless MC7750 locked in any way? **URL:** \ **Category:** Legacy AirPrime modules\ **Created:** [May 21, 2025, 7:23am UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953 "2025-05-21T07:23:21Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![cbldbssr](https://avatars.discourse-cdn.com/v4/letter/c/d6d6ee/32.png) [@cbldbssr](https://forum.sierrawireless.com/u/cbldbssr)\ **Post date:** [May 21, 2025, 7:23am UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/1 "2025-05-21T07:23:21Z")
I am facing issue as descrived in [MC7750 and `CME ERROR: SIM wrong` with various SIM cards](https://forum.sierrawireless.com/t/mc7750-and-cme-error-sim-wrong-with-various-sim-cards/29466) thread. TL;DR of that thread is: ```auto AT+CPIN? +CME ERROR: SIM wrong ``` However with different SIM cards and same SIM cards tested on Huawei modems, the problem is ONLY with Sierra Wireless MC7750 modem. I came to the conclusion that my modem is somehow locked and I came here to confirm this. How I can check it? Are there any AT commands to get confirmation of this? Could there be any other reason my SIM cards (I even bought different providers, like T-Mobile Polska or Orange Polska) are giving the error of wrong SIM? ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 21, 2025, 7:26am UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/2 "2025-05-21T07:26:20Z")
you can check with other SIM card with different operators ---
**Author:** ![cbldbssr](https://avatars.discourse-cdn.com/v4/letter/c/d6d6ee/32.png) [@cbldbssr](https://forum.sierrawireless.com/u/cbldbssr)\ **Post date:** [May 21, 2025, 7:28am UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/3 "2025-05-21T07:28:37Z")
I did. Did you read my post? ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 21, 2025, 7:29am UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/4 "2025-05-21T07:29:56Z")
not sure if it can read anything on AT+CCID and AT+CIMI i think there is some hardware issue on the sim card slot ---
**Author:** ![cbldbssr](https://avatars.discourse-cdn.com/v4/letter/c/d6d6ee/32.png) [@cbldbssr](https://forum.sierrawireless.com/u/cbldbssr)\ **Post date:** [May 21, 2025, 10:23am UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/5 "2025-05-21T10:23:07Z")
`AT+CIMI` replies with a number, below number is redacted. `AT+CCID` gives an error. ```auto AT+CCID ERROR AT+CIMI 000000000000000 ``` ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 21, 2025, 10:36am UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/6 "2025-05-21T10:36:12Z")
i think there is some hardware issue on the sim card slot ---
**Author:** ![cbldbssr](https://avatars.discourse-cdn.com/v4/letter/c/d6d6ee/32.png) [@cbldbssr](https://forum.sierrawireless.com/u/cbldbssr)\ **Post date:** [May 21, 2025, 2:05pm UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/7 "2025-05-21T14:05:42Z")
I have two modems like that, on two different hardware units and both have the same problem with different sim cards each from different provider. One hardware unit: ```auto AT!SPN? !SPN: 2, "Orange" ``` Second hardware unit: ```auto AT!SPN? !SPN: 2, "T-Mobile.pl" ``` ---
**Author:** ![cbldbssr](https://avatars.discourse-cdn.com/v4/letter/c/d6d6ee/32.png) [@cbldbssr](https://forum.sierrawireless.com/u/cbldbssr)\ **Post date:** [May 21, 2025, 2:06pm UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/8 "2025-05-21T14:06:51Z")
To be clear, both return on those different SIM cards: ```auto AT+CPIN? +CME ERROR: SIM wrong ``` ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 21, 2025, 2:13pm UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/9 "2025-05-21T14:13:24Z")
do you have a OK MC7750 modem can read those SIM cards? ---
**Author:** ![cbldbssr](https://avatars.discourse-cdn.com/v4/letter/c/d6d6ee/32.png) [@cbldbssr](https://forum.sierrawireless.com/u/cbldbssr)\ **Post date:** [May 21, 2025, 8:09pm UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/10 "2025-05-21T20:09:17Z")
I took my spare Sierra Wireless MC7455 and installed on the same hardware and everything works. I just started `pppd(8)` session on MC7455 and I have working Internet. I believe problem is with the modem. I would like to know is my modem locked somehow that I cannot use any SIM card, but maybe only Verizon’s. I don’t know where to find generic firmware for my MC7750 modem to test this theory. ---
**Author:** ![cbldbssr](https://avatars.discourse-cdn.com/v4/letter/c/d6d6ee/32.png) [@cbldbssr](https://forum.sierrawireless.com/u/cbldbssr)\ **Post date:** [May 21, 2025, 8:23pm UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/11 "2025-05-21T20:23:56Z")
I have also mini-PCIe to USB adapter which has its own SIM card slot and modem MC7750 is NOT working there either and returns also `AT+CPIN? return SIM wrong`. At this stage I’m out of ideas. I would like to test different firmware version, but the ones from [https://source.sierrawireless.com/resources/airprime/software/mc7750-firmware-package-history/](https://source.sierrawireless.com/resources/airprime/software/mc7750-firmware-package-history/) I doubt will work. I am using firmware `3.5.10.13` at the moment, but I have low expectations from firmware `3.5.10.9`. ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 22, 2025, 1:13am UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/12 "2025-05-22T01:13:06Z")
are you using a Verizon SIM card? (I remember using other SIM card, it will return SIM wrong) BTW, what is the return of AT!SELRAT? ---
**Author:** ![cbldbssr](https://avatars.discourse-cdn.com/v4/letter/c/d6d6ee/32.png) [@cbldbssr](https://forum.sierrawireless.com/u/cbldbssr)\ **Post date:** [May 23, 2025, 9:40pm UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/13 "2025-05-23T21:40:16Z")
> [@jyijyi](#): > > are you using a Verizon SIM card? No, I am not. I don’t live in US. I used SIM cards of the providers mentioned in other threads - Orange and T-Mobile. ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 24, 2025, 1:47am UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/14 "2025-05-24T01:47:51Z")
You can see the firmware download page, the firmware is for verizon [https://source.sierrawireless.com/resources/airprime/software/mc7750-verizon-approved-fw-3,-d-,5,-d-,10,-d-,13/](https://source.sierrawireless.com/resources/airprime/software/mc7750-verizon-approved-fw-3,-d-,5,-d-,10,-d-,13/) ---
**Author:** ![cbldbssr](https://avatars.discourse-cdn.com/v4/letter/c/d6d6ee/32.png) [@cbldbssr](https://forum.sierrawireless.com/u/cbldbssr)\ **Post date:** [May 24, 2025, 8:39am UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/15 "2025-05-24T08:39:27Z")
Do you know location of a firmware for MC7750 which is for any service provider? ---
**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex025/user_avatar/forum.sierrawireless.com/jyijyi/32/4766_2.png) [@jyijyi](https://forum.sierrawireless.com/u/jyijyi)\ **Post date:** [May 24, 2025, 8:54am UTC](https://forum.sierrawireless.com/t/is-my-sierra-wireless-mc7750-locked-in-any-way/34953/16 "2025-05-24T08:54:02Z")
No, i don’t quite see such firmware Btw, did you check if t-mobile poland and orange poland have available LTE band for Mc7750? > **[Orange - Poland - Wireless Frequency Bands and Device Compatibility](https://www.frequencycheck.com/carriers/orange-poland)** > > Orange (Poland) uses 1 GSM band, 1 UMTS band, 4 LTE bands, and 2 5G NR bands. Find out if your unlocked phone or mobile device will work with Orange (Poland) > **[T-Mobile - Poland - Wireless Frequency Bands and Device Compatibility](https://www.frequencycheck.com/carriers/t-mobile-poland)** > > T-Mobile (Poland) uses 1 GSM band, 5 LTE bands, and 2 5G NR bands. Find out if your unlocked phone or mobile device will work with T-Mobile (Poland)