4G Internet Setup Troubleshooting

This guide is applicable to the following device / devices:

TMU CM4

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This guide helps you diagnose and resolve common 4G connectivity issues on your AutoPi device. If you cannot access the internet while connected to the device hotspot, follow the steps below in order.

Our support team is here to help you.

If you need assistance, contact support@autopi.io.

Prerequisites

Before starting, complete the initial setup guide.

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Check SIM Card

• Confirm that your SIM card is enabled for mobile data. Test the SIM in another device (for example, a smartphone) and verify that internet access works.

• If you are using a data-only SIM, confirm with your carrier that the data plan is active and roaming is enabled when required.

• Verify that the SIM card is not PIN-locked. If it is PIN-locked, enter the correct PIN in the device advance settings.

• Remove and reinsert the SIM card, and inspect both the SIM and slot for physical damage. Bent contacts, debris, or a loose SIM slot can prevent modem detection.

• Make sure the SIM orientation is correct. The text side of the SIM card must face up, and the triangle end must point into the device.

  

caution

When inserted correctly, you should hear a small click as the card locks into position. Do not force the SIM card out after the click, as this can damage the slot. Always verify orientation before insertion.

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Check Modem Detection (Hardware)

• Connect to the device hotspot and open AutoPi Local.

• Open the terminal and run:

  cmd.run "lsusb"

• The output should look similar to this:

  

• Look for your modem in the list. The USB ID will vary depending on the modem installed in your device:

  Modem Manufacturer	USB ID
  Quectel	2c7c:0121
  Telit	1bc7:1031

• If you ordered a 4G-enabled device and the modem does not appear in the list, please contact support@autopi.io.

tip

If lsusb is unavailable, run cmd.run "dmesg | grep -i usb" to check USB detection events.

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Check Modem Setup

Check PDP Context

PDP context controls how the modem connects to the mobile network. Incorrect values can prevent data sessions from starting.

For software version 1.22.7 or newer:

modem.connection pdp_context

For older versions:

modem.connection execute AT+CGDCONT?

Expected output is either:

# Single context
value:
- apn: ''
  cid: 1
  pdp_type: IPV4V6

# Dual context (includes ims)
value:
- apn: ''
  cid: 1
  pdp_type: IPV4V6
- apn: 'ims'
  cid: 2
  pdp_type: IPV4V6

If the dual-context result causes connectivity issues, reconfigure with:

cmd.run "systemctl stop qmi-manager"
modem.connection execute AT+CGDCONT=2
cmd.run "systemctl restart qmi-manager"

Run the PDP command again to confirm the result.

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Check Firmware Switch

An incorrect firmware switch setting can prevent the modem from connecting to the network correctly.

If you are using software version 1.22.7 or newer, run:

modem.connection active_firmware_image

The expected output looks like this:

_stamp: "<current date>" 
_type: active_firmware_image
net_conf:global
storage_conf: ram  

Confirm that net_conf is set to global.

Incase your software version is older than 1.22.7, you can run the following command to get the same information:

modem.connection execute AT#FWSWITCH?'

Expected output:

Data:'FWSWITCH:40:1'

If the value does not start with 40, configure it manually:

modem.connection execute AT#FWSWITCH=40,1

Restart the device and verify again.

tip

For additional modem commands and examples, see Core Commands - Modem.

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Check APN Configuration

A missing or incorrect APN can block internet access even when the modem is detected.

note

If you are using the AutoPi SIM card (included with monthly cloud subscription), APN is pre-configured on newly shipped devices. In most cases, you can skip this section. If you want to verify manually, APN should be set to nxt20.net.

Check the current APN:

modem.connection pdp_context

If APN is missing and your carrier requires it, set it manually:

modem.connection execute AT+CGDCONT=1,"IPV4V6","<your-apn>"

Then restart the manager:

cmd.run "systemctl restart qmi-manager"

tip

If you do not know your APN, check your carrier documentation or support channel.

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Check qmi-manager Status

qmi-manager maintains the cellular data connection.

Check status:

cmd.run "qmi-manager status"

Expected response:

If needed, restart it:

cmd.run "systemctl restart qmi-manager"

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Restart the Network Interface

If qmi-manager is running but internet is still unavailable, cycle the interface:

cmd.run "qmi-manager down"
cmd.run "qmi-manager up"

If SIM detection fails on up, power down the device, check SIM orientation and seating, then try again.

Check interface state and IP address:

cmd.run "ip link show wwan0"
cmd.run "ip addr show wwan0"

If wwan0 has no IP address, the mobile session is not established.

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Adjust the MTU Setting

If connection is unstable (drops, intermittent cloud status), tune MTU. Based on your board version, the default MTU is either 1500 or 1280.

If your default is 1280, change it to 1500 and check whether the device comes online. If your default is 1500, change it to 1280 and check whether behavior improves. This quick comparison helps confirm whether MTU is causing the issue.

Apply MTU:

grains.set qmi:mtu <value>
state.sls network.wwan.qmi.config

Verify:

grains.get qmi:mtu
cmd.run "cat /etc/udhcpc/qmi.override"

Confirm that both outputs match the configured MTU.

note

• US Verizon: start with MTU 1428.
• Other carriers: start with MTU 1280.

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Check Internet and Cloud Connectivity

Test internet over cellular:

cmd.run "ping -c 5 -I wwan0 google.com"

Test AutoPi Cloud access:

cmd.run "curl -v my.autopi.io"

If ping works but cloud access fails, test DNS:

cmd.run "nslookup my.autopi.io"

If DNS fails, try a temporary public DNS value:

cmd.run "echo 'nameserver 8.8.8.8' > /etc/resolv.conf"

Then re-run ping and curl.

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Collect Logs for Support

If the issue persists, collect logs before opening a support request. Follow this guide to export relevant logs: AutoPi Logs Guide

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Summary

By this point, you should have verified:

1. SIM compatibility, orientation, and slot condition.
2. Modem detection and modem configuration (PDP and firmware switch).
3. APN settings.
4. qmi-manager and wwan0 status.
5. MTU tuning and DNS/cloud connectivity tests.

note

If you open a support case, include the full output from all commands used in this guide, along with the collected Logs.