# MC8790V SMS inquiry

**URL:** <https://forum.sierrawireless.com/t/mc8790v-sms-inquiry/8300>\
**Category:** MC/EM Series\
**Created:** [November 24, 2015, 8:22pm UTC](https://forum.sierrawireless.com/t/mc8790v-sms-inquiry/8300 "2015-11-24T20:22:45Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![qwakcookie](https://avatars.discourse-cdn.com/v4/letter/q/57b2e6/32.png) [@qwakcookie](https://forum.sierrawireless.com/u/qwakcookie)\
**Post date:** [November 24, 2015, 8:22pm UTC](https://forum.sierrawireless.com/t/mc8790v-sms-inquiry/8300/1 "2015-11-24T20:22:45Z")

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Hello there,

We use a MC8790V that is used to monitor a sensor in the field.

If we send an SMS with ‘===STATUS’, it is supposed to reply back with a status response by sms also.

However, this works only when we disable the data channel.  
If we turn data on, the modem receives the sms but does not reply. If we turn data off, it receives the sms and replies with a status by sms.

If we insert the sim in a regular smartphone, sms and data work the same time, so it’s not a carrier limitation.

Is this a modem limitation?

Thanks!

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**Author:** ![lotam](https://avatars.discourse-cdn.com/v4/letter/l/958977/32.png) [@lotam](https://forum.sierrawireless.com/u/lotam)\
**Post date:** [November 25, 2015, 2:28am UTC](https://forum.sierrawireless.com/t/mc8790v-sms-inquiry/8300/2 "2015-11-25T02:28:34Z")

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Hi qwakcookie,

Welcome to the forum!

Based on your description, seems like MC8790V was configured to use CS for SMS(?) so outgoing SMS was blocked by active data channel.

Can you check the return of:  
AT+CGSMS? // this should set 2 or 3 for your case  
AT+CGCLASS?

Thx

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<div class="post-metadata">

**Author:** ![qwakcookie](https://avatars.discourse-cdn.com/v4/letter/q/57b2e6/32.png) [@qwakcookie](https://forum.sierrawireless.com/u/qwakcookie)\
**Post date:** [November 25, 2015, 4:15pm UTC](https://forum.sierrawireless.com/t/mc8790v-sms-inquiry/8300/3 "2015-11-25T16:15:16Z")

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Hi,

Here are the modem responses:

+CGSMS: 3

OK

+CGCLASS: “A”

OK

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<div class="post-metadata">

**Author:** ![qwakcookie](https://avatars.discourse-cdn.com/v4/letter/q/57b2e6/32.png) [@qwakcookie](https://forum.sierrawireless.com/u/qwakcookie)\
**Post date:** [December 4, 2015, 2:24pm UTC](https://forum.sierrawireless.com/t/mc8790v-sms-inquiry/8300/4 "2015-12-04T14:24:24Z")

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If we set CGSMS = 1 (CS ONLY), it works. The SMS sends.

IF we set CGSMS = 3 (CS PREFERRED), it does not work.

What could it be? I can’t see why 3 would not work.

Thanks