Learn how to program a transponder key for an older Mitsubishi ASX using LAUNCH X431. Covers PIN retrieval, key registration, troubleshooting, and FAQs. DIY in 15 minutes.

How to Program an Older Mitsubishi ASX Transponder Key with LAUNCH X431

Last Updated: June 15, 2026

Quick Answer

Yes, you can program a new transponder key for an older Mitsubishi ASX using a LAUNCH X431 diagnostic tool. The process involves reading the vehicle's immobilizer data, retrieving the security PIN code, and using the X431's Immobilizer menu to register the new key. You'll need a compatible blank transponder key (typically an ID46 or ID4C chip) and, in most cases, at least one working key already in your possession. The whole procedure takes about 5–15 minutes, though extracting the PIN code can sometimes be the trickiest part.

Understanding the Prerequisites

Before you plug in your LAUNCH X431, take a few minutes to ensure everything is ready. Skipping these checks often leads to unnecessary frustration.

Identifying Your Mitsubishi ASX Key Type

Older Mitsubishi ASX models (pre-2015) typically use a Texas Instruments ID46 (TP23) transponder chip running at 125 kHz. Some variants use an ID4C chip instead, so it's worth verifying before purchasing a blank key.

You also need to determine whether your key is a flip key with integrated remote buttons or a simple valet key without remote functions. Why does this matter? Because programming the transponder (to start the engine) and programming the remote (to lock/unlock doors) are two separate procedures. Your LAUNCH X431 can handle both, but they live in different menus.

Checking LAUNCH X431 Compatibility

Most LAUNCH X431 models will work—including the X431 PAD, X431 PRO, X431 V+, and X431 Diagun—as long as they have the Mitsubishi software module installed and an active internet connection for PIN code calculations. The entry-level X431 Elite may require a paid software upgrade to access immobilizer functions.

Here are three quick compatibility checks before you begin:

Software version: Connect your X431 to WiFi and update the Mitsubishi database. Outdated software is the number one reason for PIN read failures.
OBD-II connection: Confirm the diagnostic port under your dashboard is accessible. The tool must maintain a stable connection throughout the procedure.
Battery voltage: Check that your vehicle's battery is above 12.5V. A weak battery causes communication errors during programming. If the car has been sitting for days, consider using a battery maintainer.

Step-by-Step Programming Procedure

This guide assumes you have one working key and want to add a second key. If you've lost all keys, the process changes significantly—we'll cover that in the troubleshooting section.

Phase 1: Vehicle Identification and PIN Retrieval

Connect the scanner. Turn the ignition to the OFF position. Plug the LAUNCH X431 into the OBD-II port under the dashboard. The scanner should power on automatically.
Select your vehicle. On the tablet, navigate to Diagnostics > Mitsubishi > ASX (or select your specific model year if prompted). The tool will read your VIN and identify the ECU.
Enter the Immobilizer menu. Choose System Diagnosis > Immobilizer or Body Control Module (BCM) —the exact label varies by software version.
Read the PIN code. This is the make-or-break step. Select Special Functions > Read PIN Code or Read Security Code. The X431 will attempt to calculate the code based on your VIN or ECU seed data. What happens next depends on your specific ECU:
- Sometimes the PIN appears instantly—a 4-digit number.
- Other times, the tool requires a paid online calculation through LAUNCH's server. This usually costs a small fee and takes about a minute.
- In rare cases, the read may fail entirely. If that happens, you may need a third-party PIN lookup service or a dealer-level subscription.
Important: Write down the PIN immediately when it appears. Do not close the menu until you've saved it somewhere safe.

Phase 2: Key Registration

Open the Key Programming menu. Go back to Immobilizer Functions and select Key Programming or Program New Key.
Enter the security PIN. The system will prompt you for the code you retrieved. Type it carefully. Note that some ECUs expect a 5-digit or 8-digit code rather than the standard 4 digits—check the displayed format carefully.
Choose your operation:
- Add Key: Use this if you have at least one working key already. The ECU will keep your existing keys and add the new one.
- Erase & Program All: Use this only if you have lost all keys. This wipes the key memory and requires you to program every key you own—including your original ones—from scratch.
Program the new key:
- Insert the blank, uncut transponder key into the ignition cylinder.
- Turn the key to the ON position (the dashboard lights come on, but don't start the engine).
- Wait for the X431 to display "Programming Successful" or similar confirmation.
- Turn the key back to OFF and remove it.

Phase 3: Verification and Final Steps

Test the new key. Wait at least 10 seconds, then insert the newly programmed key and start the engine. If it fires up, the transponder programming succeeded.
Check remote functions (if applicable). If your key has lock/unlock buttons, test them now. If they don't work, you'll need a separate Remote Keyless Entry Programming step—see the FAQ for details.
Clear diagnostic codes. Use the X431 to erase any immobilizer-related fault codes stored in the ECU. This prevents false check engine lights.

Troubleshooting Common LAUNCH X431 Errors

Even with careful preparation, things can go wrong. Here's how to handle the most frequent issues.

Error: "Communication Failure" or "No Response from ECU"

This is the most common error, and it usually has a simple fix:

Check your cable connection: Ensure the OBD-II cable is fully seated in both the vehicle port and the tablet adapter. A loose connection causes intermittent failures.
Reboot everything: Turn the ignition off, disconnect the scanner, wait 30 seconds, then reconnect and try again.
Update your software: Seriously—this fixes the problem more often than not. Connect to WiFi and run the latest Mitsubishi update before retrying.

Error: "Incorrect Security Code / PIN"

A PIN rejection means either the code is wrong, or you're entering it in the wrong format.

Double-check the code length: Some Mitsubishi ECUs use a 5-digit or 8-digit PIN instead of the standard 4 digits. Look carefully at the format the tool displayed.
Try VIN-based lookup: If the live PIN calculation failed, the X431 may offer a VIN-based lookup option. Enter your 17-character VIN manually and let the tool search its database.
Disconnect the battery: In some rare cases, disconnecting the car battery for 15 minutes resets the immobilizer's security counter, allowing a fresh PIN read. Use this as a last resort.

Error: "Programming Failed" After Inserting Key

If the tool accepts the PIN but fails during key registration, suspect the key blank:

Blank quality matters: Cheap, uncertified blanks often have unreliable transponder chips. Stick with reputable brands like Ilco, Strattec, or OEM Mitsubishi blanks.
Chip alignment: In flip keys, the transponder chip sits inside a separate housing. Make sure the housing snaps together correctly and the chip is positioned properly.
Key count limit: The Mitsubishi ASX immobilizer stores a maximum of 4 to 6 keys. If you've already hit that limit, you must use Erase & Program All and re-register every key you own (including your original ones) to free up space.

Frequently Asked Questions (FAQ)

Do I need a working key to program a new one for an older Mitsubishi ASX?

Yes, usually. The "Add Key" function requires the ECU to recognize an existing working key before authorizing a new one. If you've lost all keys, you'll need to use the "Erase & Program All" option, which demands higher access privileges (often via ECU serial number extraction or a dealer-level subscription). In that situation, a locksmith may be your safest bet.

Why won't my remote unlock/lock work after programming the key?

Programming the transponder and programming the remote are two separate jobs. Your LAUNCH X431 may handle both, but they live in different menus. Look for Remote Keyless Entry Programming under BCM Special Functions. In some cases, you'll need to follow a manual sequence (like opening and closing the driver's door a certain number of times) while the scanner is connected. Check your X431's Mitsubishi section for specific remote programming instructions.

Can I use any LAUNCH X431 model for this?

Most models will work as long as they have the Mitsubishi software module and an internet connection for PIN calculation. The X431 PAD, PRO, V+, and Diagun are all capable. The entry-level X431 Elite may require a paid software upgrade to access immobilizer functions. If you're unsure, consult LAUNCH's compatibility chart or contact your supplier.

How many keys can I store in an older Mitsubishi ASX?

The system typically stores 4 to 6 keys. If you try to program a seventh key, the first one you programmed will be automatically deleted. Always check your key count before attempting to add a new one.

What is the transponder chip frequency for an older Mitsubishi ASX?

Most older Mitsubishi ASX models use a 33-bit ID46 (TP23) chip operating at 125 kHz. This is a standard transponder type widely available from automotive locksmiths and online suppliers. Some very early models may use an ID4C chip, so confirm by checking your current key's internal chip number if possible.

Program Older Mitsubishi ASX Key with LAUNCH X431 | Step-by-Step Guide