GAC Vehicle Programming 

How to Replace Anti-Theft Module on GAC Trumpchi Using LAUNCH X431

• June 17, 2026
Step-by-step guide to replace the anti-theft module on a GAC Trumpchi using LAUNCH X431. Includes module removal, programming, key enrollment, and troubleshooting tips.

Published / Last Updated: June 16, 2026

Quick Answer: To replace the anti-theft module on a GAC Trumpchi using a LAUNCH X431, disconnect the battery, remove the old module (typically behind the glove box or under the dash), install the replacement, then use the X431’s IMMO function to write the VIN, match the ECU, and enroll the keys. A used module must first be “neutralized” or unlocked before programming. Always keep the X431 connected during the write process to avoid ECU lockout.

## Why Replace the Anti-Theft Module on a GAC Trumpchi?

The anti-theft module (often integrated into the BCM or a separate immobilizer unit) is the brain behind your vehicle’s security system. When it fails, you get classic symptoms: the engine cranks but refuses to fire, the security light flashes rapidly, or your key fob stops being recognized altogether. I’ve seen these failures happen after a jump-start voltage spike, water damage from a leaky AC drain, or simply age-related relay failure inside the module.

Ignoring a bad module will leave you stranded. Fortunately, with the LAUNCH X431, you can handle the replacement yourself — no dealer appointment needed. The tool works across GAC Trumpchi models including the GS3, GS4, GS5, and GN6, though the exact menu path may differ slightly by year.

## Understanding the LAUNCH X431 and the IMMO System

Why can’t you use a cheap $20 OBD scanner? Simple — factory security modules require secure access codes and manufacturer-level commands. A basic code reader can only pull DTCs, not write VINs or learn keys. The LAUNCH X431, on the other hand, provides Online Security Access (SA) — it pulls the required security codes directly from GAC’s server.

Software is critical. Before you start, make sure your X431 has the latest GAC Trumpchi software package. As of mid-2026, you’ll want V44.00 or newer. Check for updates under the app manager.

Connection method matters too. I strongly recommend using the wired VCI (Vehicle Communication Interface) instead of Bluetooth during IMMO programming. A dropped Bluetooth connection in the middle of writing EEPROM can brick the module. Wired is safer.

## Step 1: Removing the Old Anti-Theft Module

Locating the Module

On most GAC Trumpchi models, the anti-theft module hides behind the lower center console trim or near the steering column. On the GS4, for example, it’s clipped behind the glove box. On the GS5, it’s under the driver’s side dash panel. A quick search on your specific year will save time.

Document Connector Positions

Here’s where people make mistakes. Many GAC modules have two or three connectors that look identical. Before unplugging anything, take a clear photo or label each connector with masking tape. I’ve had customers plug them back incorrectly, which can short power or ground lines.

Verify Part Numbers

The new module — whether new or used — must have the same hardware number written on its sticker. That number looks like “28101245XX.” If the numbers don’t match, the X431 may reject the module or fail to program it. Don’t rely on visual similarity alone.

Critical Warning

Do not attempt to start the engine until the new module is fully programmed. A blank module has no VIN or key data. Starting the engine in that state will lock the ECU, requiring dealer-level equipment or remote unlocking services.

## Step 2: Installing the New (or Used) Module

Once the old module is out, mount the replacement and reconnect all harnesses. Keep the lower dash panel off for now — you’ll want easy access to the OBD port for the X431.

Reconnect the battery. Wait about 30 seconds for the CAN bus to stabilize. The module needs to power up and communicate with other ECUs before you start programming.

A Word on Used Modules

If you bought a module from a salvage yard or another car, it is locked to the donor vehicle. The X431 can unlock it — but only if you run the “Used Module Unlock” or “Neutralize Module” function first. Without that step, the X431 won’t be able to write the VIN. If your donor car is still available, you can also “Free” the module by performing an unlock procedure on that car before removing it.

## Step 3: Programming with the LAUNCH X431 – The Critical Step

This is where the magic happens. Follow each prompt carefully.

Enter the Immobilizer System

  1. Turn the ignition ON (engine off).
  2. On the X431, select Diagnosis → GAC Trumpchi.
  3. Choose Auto Detect (quickest) or manually select Immobilizer System.
  4. The X431 will communicate with the vehicle and display the current immobilizer status.

Security Code Retrieval

The X431 will attempt to retrieve the 4-digit security code automatically via its online subscription. In most cases, it succeeds. If it doesn’t, you’ll need the code from the dealer, or sometimes it’s printed on a grey sticker behind the glove box. Enter it manually when prompted.

The Main Programming Path

Once inside the IMMO menu, the sequence is:

  1. IMMO Functions → New Module Programming.
  2. Write VIN – Enter the vehicle’s 17-character VIN exactly as it appears on the dashboard or door pillar. Double-check each character.
  3. Match ECU – The X431 will sync the engine computer (ECU) with the new module. This step can take 30–60 seconds.
  4. Key Enrollment – Follow the on-screen prompts: turn the ignition OFF, wait 10 seconds, then turn it ON with the first key.

Never Interrupt

The X431 will show a progress bar saying “Writing EEPROM.” Do not disconnect the tool, turn off the ignition, or close the X431 app. An interruption here corrupts the module’s memory, requiring a replacement.

## Step 4: Syncing Keys and Final Testing

After the programming completes, the X431 will ask how many keys you want to enroll. Usually the answer is 2 (one master, one spare). Place each key in the ignition when prompted. The tool will learn the transponder chip inside the key fob.

The Test Sequence

  1. Remove the key.
  2. Open and close the driver’s door (this wakes up the BCM).
  3. Insert the key and turn to ON (not start).
  4. Watch the dashboard security light. If it turns OFF solid after about 2 seconds, the immobilizer is synced.
  5. Crank the engine. It should start normally.

If the engine starts but dies immediately, the immobilizer has not fully matched the ECU. Repeat the “Match ECU” step twice — I’ve found that performing it back-to-back increases success rates.

Remote Key Fob Buttons

Sometimes the door lock / unlock buttons won’t work after IMMO programming. That’s separate. Go to Body Control Module (BCM) → Remote Key Fob Programming and follow the same key enrollment process. That syncs the RF signal for the buttons.

## Troubleshooting Common LAUNCH X431 Errors

Even with careful steps, errors happen. Here’s what they mean and how to fix them.

Error Message Likely Cause Solution
Communication Failed Loose or faulty OBD cable; bent 16-pin connector Reconnect cable firmly; inspect pins. Switch to wired VCI.
Security Code Mismatch Module still locked from donor vehicle Run Neutralize Module or Used Module Unlock function first.
Function Unavailable X431 subscription lacks Online IMMO access Upgrade to PRO or Elite plan. The basic plan does not include GAC security functions.
Engine Starts Then Dies Immobilizer not synced with ECU Repeat Match ECU step twice, then re-enroll keys.

If you see “Function Not Supported by Vehicle”, update your X431 software to the latest GAC pack. If it still fails, the replacement module may be from a different generation (e.g., 2019 vs. 2023). Even with the same hardware number, internal firmware can differ.

## Cost vs. Convenience: DIY or Dealership?

Replacing the anti-theft module is one of those jobs where DIY makes financial sense — if you already own a capable diagnostic tool.

Option Estimated Cost Time Required
Dealership (labor + module) $250 – $550 1–2 hours
DIY (used module + if you own X431) $50 – $150 1–2 hours
DIY (new module + X431 subscription) $150 – $300 1–2 hours

The biggest risk? If you accidentally lock the ECU by starting the car with a blank module, you’ll need remote unlocking — which can cost another $50–$100. Still cheaper than the dealer.

For more on using the LAUNCH X431 for GAC diagnostics, check out our guide on [link to related guide on using LAUNCH X431 for GAC diagnostics].

## Frequently Asked Questions

Q: Can I use a used anti-theft module from a different GAC Trumpchi?

Yes, but only after neutralizing (unlocking) it with the LAUNCH X431. If you skip that step, the tool will throw a security code mismatch error. The unlock function is available in the IMMO menu under “Used Module Unlock” or “Neutralize Module.”

Q: How do I find the security code for my GAC Trumpchi?

The LAUNCH X431 with an active online subscription usually retrieves it directly from GAC’s server. If that fails, check the grey sticker on the back of the glove box, inside the owner’s manual, or contact a GAC dealer with your VIN.

Q: Will disconnecting the battery reset the anti-theft module?

No. Disconnecting the battery will silence the alarm and reset some BCM settings, but it will not fix a failed module. The immobilizer data is stored in non-volatile EEPROM memory that survives power loss.

Q: What if the LAUNCH X431 says “Function Not Supported by Vehicle”?

This usually means your X431’s GAC software is outdated. Update the app to the latest version. If it still fails, the replacement module may be a different generation (e.g., 2019 vs. 2023). Even if the hardware number matches, internal firmware can differ. Try sourcing an exact year-match module.

Q: Do I need to reprogram the key fob buttons (lock/unlock) separately?

Usually, yes. The IMMO programming syncs only the transponder chip (engine start). To get the door lock and unlock buttons working, go to Body Control Module (BCM) → Remote Key Fob Programming and follow the same key enrollment process.

Conclusion

Replacing the anti-theft module on a GAC Trumpchi is a delicate procedure, but with the LAUNCH X431 and a clear understanding of the neutralizing step, it is a manageable DIY job. Always use a wired connection, keep your software updated, and never attempt to start the engine before the module is programmed. If you run into trouble, repeat the ECU matching step — that resolves the vast majority of “starts then dies” issues.

About the Author: Erwin Salarda is an Automotive Service Equipment Technician based in the Philippines, specializing in computerized automotive diagnostic equipment such as OBD scanners and wheel alignment systems. Since 2012, he has been actively providing technical support, equipment installation, troubleshooting, after-sales service, and hands-on training for automotive service equipment used by workshops and automotive professionals.

He has received specialized training from international suppliers and manufacturers, including Launch X431 in Shenzhen, China, Lawrence Engineering Company in Guangzhou, China, and 3Excel Wheel Alignment Company in Shenzhen, China. Through these trainings, he developed advanced expertise in automotive diagnostics, calibration, wheel alignment systems, and computerized automotive service technologies.

Erwin Salarda provides professional after-sales support and technical training for automotive diagnostic and wheel alignment equipment, helping clients maximize the performance and proper use of their tools and systems. His experience covers equipment setup, software updates, calibration procedures, troubleshooting, and operational guidance for automotive workshops and service centers.

With more than a decade of experience in the automotive equipment industry, Erwin Salarda continues to support automotive businesses by delivering reliable technical expertise and practical training solutions.

For inquiries and equipment purchases, please visit https://carlifterph.com/

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