The Alientech KESS3 Unlock Module enables technicians to unlock previously locked Bosch MD1 and MG1 ECUs for tuning. This guide walks through the complete process using a Bosch MD1CS003 ECU from a PSA vehicle (Citroën Berlingo) as the example.
Preparation: Opening the ECU and Safety Checks
Before unlocking can begin, the ECU must be opened to expose the circuit board. Alientech provides a separate video covering the recommended tools and techniques for safely opening an ECU lid. Once the ECU is successfully opened, the circuit board is ready for the connection process.
Important safety step: When working on any ECU that has been removed from a vehicle, it is essential to refit the ECU to the vehicle after opening it and confirm that the engine still starts correctly. This verifies that no damage occurred during the opening process. If the vehicle starts as expected, you can proceed with confidence.
Why the KESS3 Unlock Module Matters
The Alientech KESS3 Unlock Module is a significant addition to the KESS3 tool because it provides unlock functionality for a huge range of previously locked Bosch MD1 and MG1 ECUs. More makes and models are being added at regular intervals. Technicians can check the full application list to see supported ECUs.
Software Setup and ECU Identification
Place the opened ECU on the Alientech BDM frame. In the KESS3 software, select the appropriate ECU type—in this example, the MD1 CS003 for PSA. Choose the Boot method and open the manual to view the required connections.
The software provides several key pieces of information:
- Warnings about refitting the ECU to the vehicle before communication
- Required equipment, including the connection module and ribbon cable
- ECU identification — verify that the ECU cover and label match the unit you are working on
- Circuit board diagram with a highlighted area showing where the connection must be made
A pro tip from the instructor: before pressing the unlock button, always take a backup of the ECU. The recommended sequence is:
- ID the ECU and confirm communication
- Take a backup (whether using a master tool or slave client tool)
- Proceed to the unlock function
Removing the Ferrite Resistor
The software instructions highlight a specific component on the circuit board: a small ferrite resistor (described as a voltage resistor) that must be temporarily removed to enable the boot connection. This step is critical and requires care.
To remove the resistor:
- Apply liquid flux to the required area
- Carefully heat the solder joints
- Remove the resistor using suitable soldering equipment
Making Bench and Boot Connections
With the ferrite removed, the software provides a step-by-step breakdown of the cables, connections, and wires required. The process involves both bench connections and a direct boot connection to the circuit board.
The KESS3 unlock module uses bridge pins (also called jumper pins) to ensure the correct current and voltage is sent to the circuit board.
Connection type: The MD1CS003 is typically a Type 2 ECU. Based on the instructor’s experience unlocking hundreds of these units, nearly all use the Type 2 connection. The only variation is the number of ground pins required. If no communication is achieved with Type 2, try Type 1 with fewer connections first before adding more.
The specific connection type depends on the software, calibration, and firmware inside the ECU, as well as the specific chipsets present.
The KESS3 unlock module includes a platine—a circuit board designed for the BDM frame—that enables a clean and precise connection to the ECU’s circuit board. A connecting cable links this platine to the unlock module.
Running the ID and Unlock Process
Once all bench connections are made and the boot pin is connected:
- Press ID — This should take only a few moments if all connections are correct
- Save the ID
- Take a backup of the ECU (strongly recommended before unlocking)
- Press the unlock button — The KESS3 unlock module completes the unlocking process automatically
Different ECUs may require connections in different locations, so always follow the instructions provided by the KESS3 in the Alientech Suite software.
Reinstalling the Ferrite Resistor
After the unlock is complete and the cables are disconnected, the ferrite resistor must be replaced on the circuit board. This step is essential: if the ferrite is not connected correctly and does not have continuity through it, the vehicle will likely experience starting or running issues.
To refit the resistor:
- Add a small amount of flux to the ferrite location on the circuit board
- Place the ferrite back into the correct position
- Apply solder to safely secure it to the circuit board
- Use a multimeter to confirm the resistance or continuity of the ferrite
Completing the Job
Once the resister is securely reinstalled and continuity is confirmed, the process is complete. The ECU is now successfully unlocked and ready for tuning—whether for performance or economy.
If tuning was performed on the bench or via boot mode, the ECU is now ready to go back into the vehicle with the new tuning software uploaded. Simply reconnect the ECU to the vehicle, and the job is finished.
