NRF9160 LTE connect error message

[Frog]

Hi,

  I'm experiencing an intermittent problem where nRF9160 devices aren't able to establish an LTE connection.  Recently our SIM provider made a configuration change that caused a number of devices to have their connections dropped, and several of them were not able to re-establish a connection for a number of days.  Many of these devices are in the field, but I was able to examine one of them and found that this message was output as the device tried to open a CAT-M1 connection:

<dbg> lte_lc_helpers: parse_cereg: LTE mode not found, error code: -22

I'm working through this with our SIM provider and would like to know if you're able to say what would cause this message to be generated?

Modem firmware is 1.3.5 and the application code is built with SDK 2.4.2.

Thanks,

  Frog

[RM]

Hi,

This message appears when act parameter of the CEREG cannot be detected,  (should be 7), means the device is not registered to a network.

Can you capture the entire log including raw responses.

Thanks,

Reuven

[Frog]

I'm not submitting AT+CEREG myself, this is being done inside Zephyr. The application code is calling

lte_lc_connect_async

I rebuilt the project with

CONFIG_LTE_LINK_CONTROL_LOG_LEVEL_DBG=y

and I see that normally there's something of the form

<dbg> lte_lc: at_handler_cereg: +CEREG notification: +CEREG: 2,"B040","00187E02",7
<dbg> lte_lc_helpers: parse_cereg: Network registration status: 2

but with the 'bad' SIM I see

<dbg> lte_lc: at_handler_cereg: +CEREG notification: +CEREG: 0
<dbg> lte_lc_helpers: parse_cereg: Network registration status: 0
<dbg> lte_lc_helpers: parse_cereg: LTE mode not found, error code: -22

Is there a debug option I can use that will output all of the AT commands and responses?  There's quite a lot of business logic-related material in the logfiles and I'm hesitant to publish it all here.

[RM]

Hi,

Based on the provided info, one of the reasons, maybe wrong APN (+CGDCONT) setting either for the SIM itself or during modem setup, the network is present, but without actual registration.

Would also limit to the operating bands in your area.

I totally understand the confidentiality issue, for me to help you further (I am not a Nordic rep), would suggest you contact me directly using mail in my profile.

Thanks,
Reuven

[Michal]

Hello Frog,

Sorry for the delays, looks like this case got by a mistake assigned to me when I was away.

Has there been any progress with that issue in the meantime?

Best regards,

Michal

[Frog]

Hi Michal,

  There's been little progress; nearly all of the devices in the field did come back online within a few days.  I have a couple of devices that still won't connect, and have found some peculiar issues where a specific combination of 9160 and SIM won't connect.  I'm not sure what I could to beyond trying to trace out the comms between the SIM and modem, unless there's a way to get the modem to output some detailed diagnostics.