Mechanic Wiki: Restore Lost Transponder Data & Recode Keys on Chery Fulwin 2 with LAUNCH X431

Step-by-step guide to restore corrupted immobilizer EEPROM data and recode keys on Chery Fulwin 2 using LAUNCH X431. Includes troubleshooting, prerequisites, and expert tips.

Published: June 15, 2026

Quick Answer: How to Restore Lost Transponder Data on a Chery Fulwin 2

If your Chery Fulwin 2 won’t start because the immobilizer has lost all key recognition, you need to restore the transponder data before programming new keys. Using a LAUNCH X431 with the correct software, the process involves: connecting to the Immobilizer Control Unit (ICU), reading and backing up the current (often corrupted) data, performing a "Restore Data" or "Initialize" function to reset the EEPROM chip (typically 24C02 or 93C46), writing a known-good blank file, and finally recoding the physical keys via the "Key Programming" menu. If the X431 fails to write over OBD, manual EEPROM removal and external programming may be necessary.

Understanding the Problem: Why Transponder Data Gets Lost

Before you grab your X431, you need to know what you’re up against. The Chery Fulwin 2 uses a Temic immobilizer system. The engine will crank but never fire when the immobilizer is active. Here’s why the data gets corrupted:

Voltage drop during ignition: A dead or weak battery while turning the key can scramble the EEPROM memory in the ICU.
Interrupted programming sessions: If a previous key coding attempt was aborted (e.g., loss of power, scanning tool disconnect), the ECU and ICU can fall out of sync.
Faulty key transponder: A damaged or cloned ID48 transponder chip can cause the ICU to enter a “fail-safe” state and erase its learned key list.
Ignition coil interference: Rare, but electrical noise from a failing ignition coil has been known to corrupt the data stream.

The result: The ICU no longer recognizes any transponder, and the engine stays locked. The fix isn’t just adding a new key — you must first restore the ICU to a usable state.

Prerequisites: What You Need Before Starting

Tool: LAUNCH X431 (Pad VII, V+, Pro3, or any X-series with the Chery software package installed and updated to the latest version).
Power: A stable 12V battery charger connected to the vehicle. Do NOT rely on the car battery alone – programming can take several minutes, and a voltage drop mid-process will brick the ICU.
OBDII connection: Verify the vehicle’s OBDII port is clean and pins 4 (ground), 5 (signal ground), and 16 (power) are intact.
Keys: At least one original key with a working ID48 transponder. If you have no keys, you will need a “All Keys Lost” procedure (covered later).
Internet: A stable Wi‑Fi or hotspot connection for the X431 to download the correct EEPROM file from the Launch database.
Optional (for advanced recovery): A soldering iron, desoldering wick, and an external EEPROM programmer (like XPROG or Tacho) if the OBD method fails.

Step-by-Step Restoration and Key Recoding Guide

Step 1: Vehicle Connection and Software Entry

Connect a battery charger to the Fulwin 2. Keep it on for the entire procedure.
Turn the ignition ON (engine off). The dashboard lights should be steady.
Plug the LAUNCH X431 into the OBDII port (located under the steering column).
Boot the X431 and select Diagnosis → Chery → Fulwin 2.
- If the tool offers Auto Search, let it detect the VIN automatically.
- Otherwise, manually select Body → Immobilizer.
The X431 will now communicate with the ICU. This may take 10–20 seconds. If communication fails, see the troubleshooting section below.

Step 2: Reading and Backing Up the Current Data

Even if the data is corrupted, you must save it.

Navigate to Immobilizer → Special Functions → Read Immobilizer Data.
The tool will display a hex dump or a file prompt. Save this file to the X431 cloud account or to a USB drive.
Why keep it? If the restore process goes wrong, a technician with an external programmer can use this file to reconstruct the ICU manually. It’s your safety net.

Step 3: Restoring the Transponder Data (The Core Fix)

From the Special Functions menu, look for one of these options:
- Restore EEPROM Data
- EEPROM Update
- Initialize IMMO
- Blank EEPROM Write
The X431 will ask for a .bin file. If you have internet, choose Online Update — the tool will search its database based on your car’s VIN and production year (Fulwin 2 models 2010–2014 are most common).
If no file is found online, select Blank EEPROM. This writes a factory‑fresh empty memory image to the ICU.
Confirm the action. The tool will warn you that all stored keys will be erased. Proceed.
Wait for the process to finish (usually 1–3 minutes). Do not touch the ignition or remove the charger during this time.

Step 4: Key Recognition Check

Turn the ignition OFF and wait 10 seconds.
Turn the ignition back ON. Watch the immobilizer warning light on the dashboard (usually a key icon or a car with a lock).
- If the light turns off after 2–3 seconds: The data restore was successful.
- If the light stays on solid or blinks: The data is restored, but no keys are learned yet. Proceed directly to Step 5.

Step 5: Recoding the Keys

From the main Immobilizer menu, select Key Programming → Add/Erase Keys.
The X431 will ask how many keys you want to program (maximum 4). Enter the number.
For the first key: Insert it into the ignition and turn to ON. The X431 will show “Key Learning Successful”.
For each additional key: Turn the ignition OFF for 3 seconds, remove the key, insert the next key, and turn ON. Repeat until all keys are learned.
Once done, the system will automatically finalize. The X431 will exit the programming session.

Test: Remove the key, wait 10 seconds, then start the engine. It should fire immediately. If not, see the troubleshooting section.

Detailed Troubleshooting for Common Issues During Recovery

Even with the correct procedure, the X431 may throw errors. Here’s how to handle them.

Error 1: “No Response from IMMO” / “Communication Failure”

Most likely cause: Low battery voltage or a bad OBDII connection.
Fix: Reconfirm the battery charger is connected. Check the OBDII pins — bent or dirty pins are common. Reboot the X431 and try again. If the error persists, try a direct J‑2534 connection (if you have the adapter) or move to manual EEPROM recovery.

Error 2: “File Not Found for This VIN” during Restore

Cause: The Launch database does not have an exact match for your Fulwin 2’s ICU hardware revision.
Fix: Use Blank EEPROM option. The tool writes a generic uninitialized image. The ICU will then accept the first key programmed as the master.
If Blank EEPROM fails: You must physically remove the ICU (typically behind the glovebox), desolder the EEPROM chip (mark it — 24C02 or 93C46), read it with an external programmer, then write a blank file using the programmer. After re‑soldering, the X431 can code keys normally.

Error 3: Key Coding Fails After Data Restore

Cause: The key’s transponder chip is damaged or not an ID48 type. Non‑OEM clone chips sometimes fail the Temic protocol check.
Fix: Use only genuine OEM keys or high‑quality ID48 transponders. Check that the chip is securely glued inside the key fob. Try the master key first — if it fails, none of the others will work.

Error 4: Engine Starts Then Dies Immediately

Cause: The ECU is still in “anti‑theft” mode. The data was restored, but the ECU hasn’t re‑learned the immobilizer.
Fix: Perform an ECU Reset. Go to Engine System → Special Functions → Reset Adaptive Values or Clear Immobilizer Learned Values. Then repeat the key coding procedure from Step 5.

Error 5: “All Keys Lost” – No Working Keys Available

Use the X431’s “All Keys Lost” function under the Immobilizer menu.
The tool will attempt to read the security PIN from the ICU’s EEPROM over OBD. If successful, it will generate the required password and allow you to program a new master key.
If the X431 cannot read the PIN: You must externally retrieve the PIN from the EEPROM dump (using a programmer). The PIN is usually stored at address 0x010–0x013 in a 24C02 chip, often obfuscated with a simple XOR or additive algorithm. Many online forums have known PIN values for specific VIN ranges.

Expert Tips & Precautions

Always backup the original file. A corrupt EEPROM is fixable; a completely dead chip (due to power cut during writing) may require a new ICU.
Do not turn off the X431 mid‑process. A power loss or tool crash can brick the ICU permanently. Use a laptop running the Launch software if your X431 battery is low.
Bench programming is safer. If you have the skills, remove the ICU and connect it to the X431 via an OBD breakout cable on a test bench. This eliminates vehicle electrical noise and voltage fluctuations.
Understand the transponder protocol. The Chery Fulwin 2 uses a Temic immobilizer with a proprietary pseudo‑random key generation algorithm. Not all aftermarket tools handle this correctly. The LAUNCH X431 is one of the few that can.
Keep your X431 software updated. Launch periodically adds new EEPROM files and bug fixes for older Chinese models. Always check for updates before starting the job.
For manual EEPROM work: Use a quality programmer like XPROG‑PRO or Tacho Pro 2020. An improper read/write can corrupt the chip beyond recovery.

Frequently Asked Questions (FAQ)

Q: Can I use a regular OBD2 scanner to restore transponder data?

A: No. A standard code reader cannot write EEPROM data or perform key learning. You need a professional bidirectional scan tool like the LAUNCH X431 with Chery-specific software.

Q: What happens if I don't have any keys at all?

A: You must first restore the transponder data (Step 3), then use the All Keys Lost function. The X431 will try to extract the security PIN from the ICU. If it fails, you need to read the EEPROM externally to get the PIN and then manually input it.

Q: How do I know if my X431 is compatible with my Fulwin 2?

A: Check the vehicle list on your X431 under Diagnosis → Chery. If “Fulwin 2” or “Fulwin 2 (CROSS)” appears, you’re good. If not, update the software. Any X431 hardware (Pad, V+, Pro3) is physically compatible.

Q: Is manual EEPROM desoldering mandatory?

A: Only if the X431 cannot write the data via OBD. Try the Blank EEPROM function first — it works in about 70% of cases. If that fails, desoldering becomes necessary.

Q: Can I use a used ICU from a scrap yard?

A: Yes, but it’s tricky. You must read the EEPROM from the donor ICU, clear the key data using the X431 (or an external programmer), and then install it. Direct installation will cause a “Pin Code Mismatch” error with the ECU because the immobilizer and ECU are paired by a unique security sequence.

Q: Why does my key still not work after programming?

A: First, verify the transponder chip is an ID48 type. Second, ensure you haven’t exceeded the 4‑key limit. Third, clean the ignition lock contacts — dirt can prevent the antenna ring from reading the chip. Finally, check that the key’s physical blade is not too worn to turn the lock cylinder fully.

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/