Step-by-step guide to recode the immobilizer on a Chery Arrizo 5 Plus after ECU swap using LAUNCH X431. Includes prerequisites, PIN entry, key learning, and troubleshooting tips.

How to Recode the IMMO Unit After ECU Replacement on a Chery Arrizo 5 Plus with LAUNCH X431

Last Updated: June 15, 2026

Quick Answer

To recode the immobilizer on a Chery Arrizo 5 Plus after an ECU swap using a LAUNCH X431, you perform an IMMO synchronization rather than cloning the old ECU. Connect the tool, navigate to Chery > Arrizo 5 Plus > IMMO, select “ECU Replacement” or “Learn Immobilizer,” follow on-screen prompts to bind the new ECU to your BCM and keys, and enter the 4-digit security PIN when prompted. The process takes about 15–30 minutes and requires a stable battery and all keys present.

Understanding the IMMO System on the Arrizo 5 Plus

The immobilizer system in the Chery Arrizo 5 Plus relies on three critical components working together:

Engine ECU – Manages fuel injection and ignition; it will not allow the engine to run unless it receives the correct security handshake.
Body Control Module (BCM) – Acts as the immobilizer master. It stores the security IDs for all authorized keys and communicates with the ECU.
Key Transponder – Each key contains a small chip that transmits a unique ID when the ignition is turned on.

When you replace the ECU with a new or used unit, that new ECU has a different security ID — or a virgin state — that does not match the BCM. The result is a car that cranks but never starts. That’s why you need to recode the IMMO unit after ECU replacement to synchronize these three elements.

Why Cloning Won’t Work Here

Many technicians assume they can simply clone the old ECU data. However, on modern Chery models like the Arrizo 5 Plus, the IMMO system uses rolling codes and encrypted handshake protocols. Cloning the EEPROM from the old ECU may work on some platforms, but the LAUNCH X431 approach is different: you perform an ECU adaptation that authenticates the new ECU with the existing BCM and keys. This is safer and avoids potential bricking of the donor ECU.

OEM vs. Aftermarket ECUs

New OEM ECU: Comes in a virgin state. The X431 can write the VIN and security data directly.
Used OEM ECU: Still contains its previous vehicle’s security data. You must either virginize it externally (specialist tool or service) or synchronize it via the X431 if the tool supports “relearn” for used ECUs.
Aftermarket/Reman ECU: Often sold pre-virginized. The X431 will treat it like a new OEM unit.

The LAUNCH X431 can handle new and used ECUs as long as the used unit hasn’t been permanently locked due to too many failed IMMO attempts.

Prerequisites: What You Need Before Starting

Rushing into an IMMO procedure without preparation is the fastest way to lock an ECU permanently. Here’s what I’ve learned from performing dozens of these on Chery models.

Tool Requirements

LAUNCH X431 model: V+, Pro, PAD VII, or any X431 with full CAN bus support. The newer the model, the more reliable the IMMO functions.
Software: Ensure you have the latest Chery software pack installed. Navigate to the “Update” section on your X431 and download any pending updates for the Chery/Arrizo 5 Plus profile.
Subscription: The IMMO/Key Programming function often requires an active subscription. Verify that your X431 account has “IMMO” or “Special Functions” enabled.

Vehicle Preparation

Battery voltage: Below 12.5V can cause communication dropouts. Connect a battery maintainer if needed. A partially charged battery is one of the most common causes of failed IMMO procedures.
All keys: You must have every key that will be used with the vehicle. The X431 will typically learn all keys in one session. Losing a key later means repeating the entire procedure.
Key condition: For smart keys (keyless entry), ensure the key battery is fresh. For flip keys, verify the transponder chip is present — some cheap aftermarket flip keys omit the chip entirely.
Security PIN: You need the 4-digit immobilizer PIN. The X431 can sometimes calculate it from the VIN, but this requires an online subscription. Alternatively, you can obtain the PIN via a dealer login or third-party PIN retrieval service. Without the correct PIN, the IMMO process will fail after the first attempt, and some ECUs allow only a few retries before locking.

Navigating the X431 Menu

The path to the IMMO function is:

Diagnostics → Chery → Arrizo 5 Plus → Auto Detect Model → IMMO (Immobilizer) / Anti-Theft

If “IMMO” does not appear, check under “Special Functions” or use the Topology Map function to locate the immobilizer module.

Step 1: Initial Diagnosis and Error Code Clearing

After physically installing the new ECU, connect the LAUNCH X431 via the OBDII port. Perform a full system scan. Here are the typical codes you’ll encounter:

Code	Description
P0633	Immobilizer Key Not Programmed
B3054	Key Transponder Mismatch
U0100	Lost Communication with ECM/PCM
U0422	Invalid Data Received from BCM

Clear old codes first. Some generic codes may persist from the old ECU’s data. Clearing them before starting the IMMO procedure prevents confusion during the verification step later.

Important: Do not clear codes that are actively updating — wait for the scan to finish, then clear and re-read to confirm only IMMO-related faults remain.

Step 2: The IMMO Recoding Procedure (Core Process)

This is where the actual ECU adaptation happens. Follow these steps carefully.

2.1 Navigate to the IMMO Function

With the X431 connected and ignition ON (engine off), go to:

Chery → Arrizo 5 Plus → IMMO → IMMO/ECU Replacement

Some software versions call it “Learn Immobilizer” or “ECU Adaptation.” If you see multiple options, choose the one that mentions “ECU Replacement” first.

2.2 Select the ECU Type

The X431 will ask whether the new ECU is:

New (Virgin) – Proceed to write VIN and security data.
Used – The tool will attempt to synchronize without wiping the previous data. This works if the used ECU is not locked and the X431 has the capability — check the on-screen message.

2.3 Data Transfer and Key Learning

The tool will now communicate with the BCM to read the current key IDs and then bind them to the new ECU.

If the X431 supports data transfer: It will read the BCM’s security matrix and write it to the new ECU. This is a one-way push.
Otherwise: The tool will prompt you to turn the ignition off and on with each key. Insert key #1, turn to ON (do not start), wait for the X431 to confirm the transponder ID. Repeat for all keys.

Crucial: When the X431 asks for the 4-digit security PIN, enter it exactly. A wrong PIN may freeze the ECU after 2–3 attempts. If you are unsure, verify the PIN before starting.

2.4 Completing the Synchronization

After all keys are learned, the X431 will display “IMMO Synchronization Successful” or a similar message. Do not turn off the ignition until the tool instructs you to do so. Some procedures require a full power cycle (key off, wait 10 seconds, key on).

Step 3: Verification and Final Checks

You have completed the recoding — but don’t celebrate until you verify everything works.

Clear Residual Codes

After the procedure, there will likely be some temporary communication faults (U-codes). Use the X431 to clear all DTCs in both the ECU and BCM.

Start Test

Turn the key to start. The engine should fire immediately. If it cranks but does not start, do not continue cranking — stop and re-check the PIN and key learning steps.

Check the Security Light

On the dashboard, the security light (often a car/lock icon) should illuminate for 2 seconds when you turn the ignition ON, then turn off. If it stays on or flashes, the IMMO is not fully synchronized.

Verify Key Count

Within the X431 IMMO menu, there is usually a “Read Key Status” or “Key Count” option. Use it to confirm that all your keys are recognized. If a key is missing, repeat the learn procedure for that key only.

Remote Lock/Unlock

Test the key fob functions. Since the BCM was not replaced, remote functions should work as before. If not, check the BCM communication codes and clear them.

Troubleshooting Common IMMO Issues with LAUNCH X431

Even experienced technicians hit roadblocks. Here are the most common problems and solutions based on real-world use.

“Cannot Connect to IMMO”

Check CAN bus wiring: The new ECU may have different pinouts if it’s a used unit from another year. Verify the CAN high/low wires at the OBDII port.
Check ground points: Poor ground at the BCM or ECU can interrupt the IMMO handshake.
Fuse F: The immobilizer circuit is often on a specific fuse. Consult the owner’s manual or fuse box diagram. Replace if blown.

“Code Not Available” (PIN Request)

The X431 cannot guess the PIN — it relies on an online database. If your subscription does not include PIN retrieval, you need a third-party service. Common sources include:

Dealer-level diagnostics (Chery service login)
Paid PIN lookup services (many work via VIN + X431 teamviewer support)
EEPROM dump from the old ECU (advanced, not recommended in the field)

“Key Learning Failed”

No transponder: Some aftermarket flip keys are just shells with no chip. Open the key and confirm.
Low key battery: For smart keys, replace the coin cell battery (CR2032) before starting.
Antenna ring issue: The transponder antenna ring around the ignition lock may be damaged or too far from the key. Move the key closer or check the antenna wiring.

“ECU is Locked”

If the X431 reports that the ECU write counter has reached its limit, the ECU is permanently locked. This happens when a used ECU had multiple failed IMMO attempts. The only solutions are:

Replace the ECU with a virgin unit.
Send the ECU to a specialist for hardware unlocking (not available via X431).

Pro tip: Always ask the customer whether the new ECU came from a known working vehicle. If it was from a scrapped car that was “recycled,” there’s a high chance the ECU is locked.

Advanced Considerations: Second-Hand ECUs and Remote Start

Resetting a Used ECU to “Virgin” Status

The LAUNCH X431 does not have a “virginize” function for Chery ECUs. This requires specialist tools (e.g., KTAG, BDM100) or sending the ECU to a service center. Do not claim otherwise to customers.

If you plan to use a used ECU, your best bet is:

Try IMMO synchronization directly (it works on some used ECUs if the previous vehicle’s data is still intact).
If that fails, virginize the ECU externally or replace it with a new OEM part.

Remote Start Integration

If the vehicle has an aftermarket remote start module, the IMMO recoding does not affect it directly. However, the remote start module typically uses a “key bypass” that clones the transponder signal. After IMMO recoding, you may need to relearn the bypass module. The X431 can help by verifying that all keys are recognized before you re-pair the remote start.

VIN Matching

The new ECU will not start storing the correct VIN until after successful IMMO synchronization. Some X431 software versions allow you to manually write the VIN under “ECU Programming” > “VIN Write.” This is not always required for starting, but it helps with future diagnostics and emissions testing. If the option is available, write the VIN after the IMMO procedure is complete.

Frequently Asked Questions

Can I use any used ECU from a scrapped Arrizo 5 Plus?

Yes, but only if the used ECU is not locked and you synchronize it with your BCM and keys using the LAUNCH X431. If the donor ECU has been locked due to failed IMMO attempts, you must virginize it externally before use. Swapping both the BCM and keys from the donor vehicle is not practical here.

How long does the IMMO procedure take with the X431?

Plan for 15 to 30 minutes total. This includes connecting the tool, reading codes, performing the key learning, and verifying everything works. The actual learning step takes only 2–3 minutes per key.

What if I lose connection during the IMMO process?

Keep the ignition ON. Reconnect the X431 immediately and run an “Auto Scan” for the IMMO system. The tool may resume the procedure from where it left off. Do not turn the battery off — that can corrupt the partial data transfer and lock the ECU.

Will this procedure delete my service light or other adaptations?

No. The IMMO procedure strictly affects the security matrix between the ECU, BCM, and keys. Maintenance lights (service reminder) remain as they were. If you need to reset the service light, use the X431’s “Service Reset” function separately.

Does the LAUNCH X431 support all Chery models for this?

The X431 supports the Arrizo 5 Plus, including 2022+ facelift models, but only with the latest software. Before starting, check that the “IMMO/ECU Replacement” function appears under the Chery menu. If you are working on a very new 2025 model, confirm with LAUNCH support that the software covers that specific year.

Final Thoughts

Recoding the IMMO unit after ECU replacement on a Chery Arrizo 5 Plus is a straightforward procedure when you have the right preparation — stable battery, correct PIN, and all keys in hand. The LAUNCH X431 handles the heavy lifting, but the success of the job ultimately depends on your attention to detail.

If you are new to IMMO work, start with a known-good vehicle and take your time reading each on-screen prompt. And remember: if the engine starts and the security light goes off, you’ve done it right. For more guidance on related diagnostic tasks, check out our guide on [link to related guide on ECU replacement procedures] or our article on [link to tips for using LAUNCH X431 on 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/

How to Recode IMMO Unit After ECU Replacement on Chery Arrizo 5 Plus with LAUNCH X431