> For the complete documentation index, see [llms.txt](https://docs.verifone.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.verifone.com/support-us/network-configurations-and-errors/network-troubleshooting/comm-error/engage-comm-error-diagnostics.md).
# Engage Comm Error Diagnostics
Includes directions for terminal models: P400, e235, e280, e285, P200, P400, V200c, V240m, V400c, V400m, m400, m424, m440
{% hint style="info" %}
**Use this when** basic Comm Error troubleshooting hasn't resolved the issue and you need deeper hardware or network configuration diagnostics.
{% endhint %}
Common causes for communication errors include hardware connection problems and network settings that need adjusting.
## Resolve the issue
{% stepper %}
{% step %}
### Check the hardware
Check the peripheral connections at the back of the device. If your setup allows, ensure each cable is securely plugged in; reconnect or secure anything loose.
* If a peripheral is broken, get its part number (P/N) and replace it — contact your Merchant Services Provider, Level 1 Helpdesk, or Verifone Helpdesk.
Confirm the power outlet is functional; switch to a known-working outlet to test.
If your site setup permits, move the device — without its cables — to a known-working station to isolate the issue.
* If the issue follows the device, the device itself may need replacement.
* If the issue does not follow the device, one of the peripheral cables is the cause — isolate further to find which one.
✅ **Issue fixed — stop here.** ❌ **Still not working — continue to the next step.**
{% endstep %}
{% step %}
### Check the network configuration
Verify the device's current network configuration:
* **Account setup:** get the correct values from your Level 1 Helpdesk, Merchant Services Provider, or Verifone Helpdesk, if applicable.
* **DHCP:** automatically assigns IP addresses and other settings (subnet mask, gateway, DNS servers) to devices.
* **Static:** provides a fixed IP address and configuration, commonly used for added security.
If any of these are set incorrectly, they need to be adjusted to resolve the Comm Error.
{% hint style="danger" %}
Only use the network details provided by your network manager. Incorrect details can prevent successful device pairing and transactions.
{% endhint %}
✅ **Issue fixed — stop here.** ❌ **Still incorrect — use the update guide below.**
{% endstep %}
{% endstepper %}
## Update the network configuration
Choose the method that matches your device's interface.
{% tabs %}
{% tab title="System Mode" %}
{% stepper %}
{% step %}
### Open system mode
Press `1`, `5`, and `9` simultaneously. A sub-menu appears — press `1`, `5`, and `9` together again. Select **Supervisor**, then enter the device password (default `1668321`, unless changed).
{% hint style="warning" %}
If the default password doesn't work, contact your Merchant Services Provider, Level 1 Helpdesk, or Verifone Helpdesk for the password.
{% endhint %}
{% endstep %}
{% step %}
### Navigate to Ethernet settings
Press the green **(o)** button to open the system mode menu. Select **Administration** → **Communications** → **Ethernet** → **eth0**.
* If `eth0` isn't available, check the peripheral cables, focusing on the Ethernet connection.
* If it becomes available after reconnecting, continue to the next step.
* If it's still not available, contact your Merchant Services Provider, Level 1 Helpdesk, or Verifone Helpdesk.
{% endstep %}
{% step %}
### Adjust the network values
Select **Ethernet**, then view and adjust: **IP Address**, **Subnet Mask**, **Gateway IP Address**, **DNS1**, **DNS2**.
{% endstep %}
{% step %}
### Save and reboot
Tap the arrow at the top left of the screen and select **Yes** to save. Then reboot by tapping the arrow at the top right until you reach the main menu and selecting **Exit** → **Reboot**, or hold the red **(X)** button.
{% endstep %}
{% endstepper %}
{% endtab %}
{% tab title="Comm Control" %}
{% stepper %}
{% step %}
### Open Comm Control
Press `1`, `5`, and `9` simultaneously. Select **Comm Control** → **More** → **Configuration**, then enter the Comm Control password.
{% hint style="warning" %}
If the default password doesn't work, contact your Merchant Services Provider, Level 1 Helpdesk, or Verifone Helpdesk for the password.
{% endhint %}
{% endstep %}
{% step %}
### Open the network interface settings
Select **Network Interface** → **Ethernet** or **LAN** → **Configuration** → **IPv4**. Select **DHCP**, then select **No**.
{% endstep %}
{% step %}
### Adjust the network values
View and adjust: **IP Address**, **Subnet Mask**, **Gateway IP Address**, **DNS1**, **DNS2**.
{% endstep %}
{% step %}
### Save and apply
Press the red **(X)** button or tap the top-left arrow to go back. Select **Save** → **OK** → **Yes** to apply. Once the device shows "Accepted," select **OK**.
{% endstep %}
{% step %}
### Reboot
Tap the top-left arrow, select **Exit** → **Yes**, then hold the red **(X)** button or select **Reboot** to power-cycle the device.
{% endstep %}
{% endstepper %}
{% endtab %}
{% endtabs %}
{% hint style="info" %}
To learn more about accessing a device's settings to view its current setup, see [Device Settings](/support-us/general-pinpad-support/general-pinpad-help/device-settings.md).
{% endhint %}
Keywords
Also called: engage diagnostics, comm error deep troubleshooting, network config update. Search terms: comm error diagnostics, system mode, comm control.
---
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