> For the complete documentation index, see [llms.txt](https://commanderhelp.verifone.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://commanderhelp.verifone.com/customer-documentation/petro-and-c-store/pin-pads/implementation-guides/m400/troubleshooting.md).

# Troubleshooting

This section lists typical malfunctions that may occur while operating a Verifone M400 device and the appropriate corrective action. If the problem persists, even after performing the outlined guidelines, or if the problem is not described, contact your local Verifone representative for assistance.

{% hint style="info" %}
The Verifone M400 device uses a tamper-evident case and contains no user-serviceable parts. Do not, under any circumstance, attempt to disassemble the unit. Perform only those adjustments or repairs specified in this guide. For all other services, contact your local Verifone service provider. Service conducted by parties other than authorized Verifone representatives may void any warranty.
{% endhint %}

### Calibrate Touch Panel

The terminal requires a touch screen calibration at the time of installation. The terminal should be powered on and allowed to stabilize at normal operating temperature; usually this takes no longer than 60 seconds, even if the terminal was previously in a cooler or warmer location. The touch screen calibration procedure should then be performed. Also, while in System Mode, verify the time on the unit is correct.

#### Calibrating the Touch Screen

{% stepper %}
{% step %}

#### Navigate to System Mode

Navigate to System Mode.
{% endstep %}

{% step %}

#### Enter System Mode

If an application is already loaded and running, put the Verifone M400 PINpad into System Mode by pressing keys 1, 5, 9 at the same time on the keypad. If there is no application loaded, the terminal will boot up to the System Mode Login Screen.
{% endstep %}

{% step %}

#### Sign in

Login using Supervisor user profile.
{% endstep %}

{% step %}

#### Open touch calibration

Select Administration.

Select Calibrate Touch Panel.
{% endstep %}

{% step %}

#### Start calibration

A message is displayed on the screen, press OK to start calibration.
{% endstep %}

{% step %}

#### Follow on-screen instructions

Follow on-screen prompts or instructions.
{% endstep %}
{% endstepper %}

### Display Panel Does Not Work

Use the following steps to check the display panel:

{% stepper %}
{% step %}

#### Check cable connections

Check all the cable connections.
{% endstep %}

{% step %}

#### Check the power outlet

Check the controlling device's AC outlet to be sure the outlet is supplying sufficient power. Substitute the controlling device's power pack with another power pack.
{% endstep %}

{% step %}

#### Reload the application

The controlling device's application program might not be loaded correctly. Download the application program and try again.
{% endstep %}

{% step %}

#### Contact the Helpdesk

If the problem persists, contact the Verifone Helpdesk.
{% endstep %}
{% endstepper %}

### Keypad Does Not Respond

Use the following steps to check the keypad:

{% stepper %}
{% step %}

#### Check the display panel

Check the display panel. If there are no characters, or the wrong characters are displayed, see Display Panel Does Not Work above.
{% endstep %}

{% step %}

#### Contact the Helpdesk

If the problem persists, contact the Verifone Helpdesk.
{% endstep %}
{% endstepper %}

### Transactions Fail To Process

There are several possible reasons why the unit may not be processing transactions. Use the following steps to troubleshoot failures.

#### Check Magnetic Card Reader

* Perform a test transaction using one or more different magnetic stripe cards to ensure the problem is not a defective card.
* Ensure that you are swiping cards properly (see Magnetic Stripe Card Reader Use).
* Process a transaction manually using the keypad instead of the card reader. If the manual transaction works, the problem may be a defective card reader.
* If the problem persists, contact the Verifone Helpdesk.

#### Check Smart Card Reader

* Perform a test transaction using several different smart cards to ensure the problem is not a defective card.
* Ensure that the card is inserted correctly (see Smart Card Reader Use).
* If the problem persists, contact the Verifone Helpdesk.


---

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