Launch X431 

How to Change Units (Metric vs. Imperial) on Launch X431 | Step-by-Step Guide

• April 24, 2026
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Learn how to switch between metric and imperial units on your Launch X431 scanner. Includes global settings, app-specific changes, troubleshooting, and FAQs for accurate diagnostics.

Quick Answer

To switch between metric and imperial units on your Launch X431, change the global setting in System Settings > Unit. For specialized functions like TPMS or oscilloscope, change the unit within the specific application's own menu, as these often operate independently.

Why Getting the Units Right on Your Scanner Matters

Using the correct unit system—metric (SI) or imperial (US customary)—is a fundamental step in accurate automotive diagnostics. A misread measurement can cascade into incorrect part replacements, faulty adjustments, or overlooked problems. Whether you're checking tire pressure in PSI versus bar, interpreting coolant temperature in °C versus °F, or reviewing live data, consistency with your workshop manuals and familiarity is key. This guide applies to the popular Launch X431 series, including the X431 V, PAD V, PAD VII, and CRP models.

Method 1: Changing the Global Default Unit System

This method sets the primary unit standard for most general functions on your device, such as the main menu display and generic live data parameters.

  1. From the device's home screen, locate and tap the Settings icon (typically a gear symbol). On some interfaces, this may be labeled User Settings.
  2. Within the settings menu, select System Settings.
  3. Scroll through the options until you find Unit.
  4. Tap on Unit. You will be presented with a choice:
    • Metric (SI): Kilometers (km), km/h, Celsius (°C), bar, liters (L).
    • Imperial (US): Miles (mi), mph, Fahrenheit (°F), psi.
  5. Select your preference. The change is usually applied immediately. Exit the menus and navigate to a live data stream to confirm the new units are displayed.

Method 2: Changing Units Within Specific Applications

Many advanced diagnostic and service functions have their own, independent unit settings. The global setting does not override these.

  • TPMS Service: This is the most common example. When programming or checking tire pressure sensors, you must set the desired pressure unit (psi, bar, kPa) within the TPMS application itself. Look for a "Settings," "Config," or "Unit" option after entering the TPMS tool. For official procedures, refer to the Launch TPMS application guide.
  • Oscilloscope & Multimeter: These tools feature dedicated unit selection buttons or on-screen menus on their main display to switch between V, mV, Hz, ms, etc.
  • Activation Tests & Special Functions: Some bidirectional control tests may display values with a toggleable unit.

Pro Tip: If a reading looks off, scan the screen for a unit label (e.g., "kPa"). Often, you can tap directly on this label to cycle through the available unit options for that specific parameter.

Detailed Troubleshooting: What to Do If You Can't Change Units

If the unit change isn't reflecting where you expect, follow this systematic approach.

Step 1: Verify the Global Setting Took Effect

Fully exit all menus. Enter a standard diagnostic session and view a live data parameter like engine RPM or vehicle speed. Verify if the units have changed here first.

Step 2: Check the Specific Application's Settings

Remember that specialized apps operate independently. Enter the app in question (e.g., the oscilloscope) and meticulously look for its own Settings, Options, Config, or a gear icon within that app's environment.

Step 3: Consider Vehicle ECU Communication

In some cases, the vehicle's ECU may transmit a particular data parameter in a fixed unit. The scanner can only display what it receives. Consult the vehicle's factory service information to confirm.

Step 4: Update Your Diagnostic Software

An outdated version of a specific application may contain a bug affecting unit display. Connect your Launch X431 to Wi-Fi and check for updates via the X431 Shop or the dedicated software update utility in your device's settings.

Step 5: Perform a Device Reboot

A full restart can clear temporary software glitches. Power down your X431 tablet completely, wait a moment, and then power it back on. Recheck the unit settings afterward.

Step 6: Reset to Factory Settings (Use with Caution)

As a last resort, a factory reset can resolve deeper software issues. Warning: This will erase all user profiles, custom settings, saved vehicle data, and paired Bluetooth/Wi-Fi connections.

  1. Go to Settings > System > Reset Options (path may vary slightly by model).
  2. Select Erase all data (factory reset) and confirm.
  3. After the device reboots and completes setup, reconfigure your unit preferences from scratch.

Related Settings to Configure

For a complete setup, consider adjusting these related parameters in your device settings:

  • Language: Set the interface language under System Settings.
  • Date & Time: Crucial for accurate time-stamping on diagnostic reports and data logs.
  • Pressure Coefficient: An advanced setting for fine-tuning pressure sensor readings, relevant for precise measurement tools.

FAQ: Launch X431 Unit Settings

Does changing the unit system affect all my saved data and reports?

No, changing units is a display-level setting. Previously saved diagnostic reports and data logs will retain the units in which they were originally recorded. New data captured will reflect the new unit setting.

My TPMS tool still shows bar, but I set the system to Imperial. Why?

The TPMS application is a standalone program with its own configuration. You must change the pressure unit within the TPMS app's own settings menu before initiating sensor service or reading pressures.

Can I set different units for different vehicles?

The Launch X431 uses a global device setting for units. It does not create per-vehicle profiles for this preference. You would need to manually switch the global unit setting when switching between vehicles that require different measurement systems.

What's the difference between "Imperial" and "US" unit settings?

On the Launch X431, these terms are typically used interchangeably to refer to the same system: miles, Fahrenheit, pounds per square inch (psi), etc. The menu will usually offer just one such option.

Will the wrong units cause my scanner to give false trouble codes?

No. Diagnostic Trouble Codes (DTCs) are triggered by the vehicle's ECU and reported as standardized code numbers (e.g., P0301). Display units do not affect code retrieval. However, misinterpreting the numeric live data or freeze frame data (like a 100°C reading vs. a 212°F reading) due to incorrect units can absolutely lead to a faulty diagnosis.

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