Mechanic Wiki: How to Read the PIN Code on a GAC Trumpchi GS4 Using LAUNCH X431

Step-by-step guide to retrieve the GAC Trumpchi GS4 PIN code for key matching using LAUNCH X431. Includes troubleshooting, FAQ, and alternative methods.

Published: June 16, 2026

Quick Answer: How to Retrieve the GAC Trumpchi GS4 PIN Code

To read the PIN code on a GAC Trumpchi GS4 using a LAUNCH X431, you don’t need to disassemble the dashboard or hunt for hidden chips. Simply connect the X431 to the OBDII port, turn the ignition to ON, select Diagnostics > GAC > Trumpchi > GS4, then navigate to Immobilizer (IMMO) > Special Function > Read Security Code. The tool communicates with the ECU or BCM and displays a 4‑digit PIN within 30–90 seconds. Write it down exactly — you’ll need it for key matching.

Understanding the Basics: GAC Trumpchi GS4 Immobilizer Systems

Why You Need the PIN Code

The PIN code acts as a cryptographic handshake between your LAUNCH X431 and the vehicle’s immobilizer system. Without it, the diagnostic tool cannot authorize the pairing of a new key transponder. This security measure prevents unauthorized duplication and theft — so every time you program a spare or replacement key, the PIN is mandatory.

Tools Required: Choosing the Right LAUNCH X431 Model

Not every LAUNCH scanner supports this procedure. You’ll need a bi‑directional model like the X431 V+, PAD VII, PRO3, or any newer unit with full GAC software support. Before you start, update your X431 via Wi‑Fi — go to Diagnostics > Update and ensure the GAC package is current. Look for release notes that mention “Trumpchi GS4 Immobilizer” features. An outdated version often grays out the PIN read function.

Where the PIN Is Stored (The Machine View)

The PIN is encrypted inside the Engine Control Unit (ECU) for most GS4 model years. Some variants store it in the Body Control Module (BCM) as a backup. The physical key’s transponder chip does not reveal the PIN directly — the X431 must decrypt the code via OBDII communication. If the ECU has been replaced with a used unit, the stored PIN belongs to the donor vehicle, not your car. In those cases, you may need to run a PIN Relearn procedure first.

Step‑by‑Step Guide: Reading the PIN Code

Preparation

Check battery voltage. The system needs at least 12V. If the battery is weak, attach a battery support charger to avoid voltage drop during communication.
Turn the ignition to ON. Do not start the engine. Just turn the key (or press the start button without your foot on the brake) until the dashboard lights come on.
Connect the LAUNCH X431. Plug the main diagnostic cable into the vehicle’s OBDII port — typically located under the dashboard, left of the steering column.
Power up the scanner. The X431 will boot automatically once plugged into a live port.

Accessing the Immobilizer System

On the LAUNCH home screen, tap Diagnostics.
Select GAC → Trumpchi → GS4.
Choose your vehicle’s specific Engine type and Model Year from the drop‑down lists.
Tap Immobilizer (IMMO) .
If you don’t see an “Immobilizer” option: Look under System Selection and choose BCM (Body Control Module) or ECM (Engine Control Module) — the PIN read function may be nested inside one of these modules.

Executing the PIN Read Function

Inside the Immobilizer menu, select Special Function or Security Access (name varies by software version).
Tap Read Security Code or Read PIN Code.
The tool will now initiate a handshake with the ECU or BCM. This takes 30 to 90 seconds. Do not touch any cables or turn off the ignition during this process.
Success: A 4‑digit number appears on screen — for example, PIN: 5683.
Failure: If the function returns “Failed” or “Code Not Found,” proceed to the troubleshooting section below.

Documenting the Code

Write the PIN down clearly in two separate places. Common mistakes include confusing the digit 0 with the letter O, or swapping 6 and 9. Double‑check each numeral before closing the diagnostic session.

Common Pitfalls & Troubleshooting

1. The Read PIN Function Is Grayed Out

Cause: Your X431 software version is too old to support this specific GS4 model year.
Fix: Update the scanner via Wi‑Fi. Go to Diagnostics > Update and install the latest GAC package. After the update, reboot the tool and try again.

2. Error: “Communication Failed”

Cause: Poor OBDII connection or low battery voltage.
Fix: Disconnect and reconnect the cable firmly. Use a multimeter to check the vehicle battery — if it reads below 12.2V, jump‑start the car or attach a charger. A voltage drop during the handshake is the most common cause of communication errors.

3. Error: “Security Code Not Found”

Cause: The specific ECU/BCM version on your GS4 does not support the generic PIN read function via OBDII.
Fix: You’ll need an alternative method (see the FAQ and the alternative method section below). In many GS4s, the PIN is physically printed on a sticker attached to the immobilizer control box.

4. Cloning vs. PIN Reading

The X431 reads the existing security code from the vehicle’s memory. If the ECU was replaced (e.g., from a junkyard), the stored PIN belongs to the donor car. In that scenario, you may need to run a PIN Relearn or ECU Initialization procedure before you can read the correct PIN for your car. For more details on this process, check out our guide on [link to related article about ECU initialization for Chinese vehicles].

Comprehensive FAQ Section

Q1: Where else can I find the PIN code if the X431 cannot read it?

If the OBDII method fails, look for the Immobilizer Control Box (sometimes called the IMMO box or BCM). On the GAC Trumpchi GS4, this box is typically located behind the glove box or under the dashboard on the passenger side. Remove the glove box (usually held by clips or a few screws) and inspect the metal or plastic module. Look for a small white or silver sticker with a 4‑digit code printed on it — that’s your PIN.

Q2: Can I program a key without the PIN code?

No. The PIN is a mandatory step before the X431 will authorize key matching. Without it, the tool cannot synchronize a new transponder to the GAC Trumpchi GS4’s immobilizer system. You must obtain the PIN — either by reading it via OBDII or by physically locating it on the module sticker.

Q3: Is the PIN code the same as the key cut code?

No. The PIN Code is an electronic security password used by the immobilizer system. The Key Cut Code (also called the key blank number or mechanical code) determines the shape of the metal key blade. Do not confuse the two — you need both for a complete key replacement.

Q4: Does the LAUNCH X431 need to be online to read the PIN?

No. The PIN is calculated locally by the tool’s software using the data received from the vehicle’s ECU. You do not need an active internet connection during the actual reading. However, the software must be up‑to‑date before you start, and some advanced functions may require an online subscription for activation.

Q5: Will reading the PIN code erase existing keys?

No. Reading the PIN is a passive diagnostic operation. It only retrieves the stored code without modifying any vehicle memory. Erasing keys happens later during the Key Learning step, when you instruct the X431 to add or delete transponders.

Q6: My X431 shows “Enter Password” – what do I enter?

For some GAC models (rarely the GS4), the tool may request a “super‑password” from the manufacturer before it attempts to decrypt the ECU. If you see this prompt, you typically need to contact LAUNCH technical support or consult an online professional locksmith forum. In most cases, the GS4 does not require this extra step.

Alternative Method: Using the T‑Code (If X431 Fails)

If the OBDII read function keeps failing and you cannot locate the immobilizer box sticker, another option is the T‑Code method. Some multi‑brand key programmers calculate the PIN by reading the transponder ID (T‑Code) from an existing key placed near the ignition coil. The tool then uses an algorithm to derive the PIN from that ID. This method is slower but can work when the direct X431 read is blocked by a software limitation.

To access this method, you would need a compatible key programmer that supports T‑Code calculations for the GAC Trumpchi GS4. For a deeper comparison of diagnostic tools, see our article on [link to related guide about key programmers for Chinese vehicles].

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/