Mercedes W245 OM640.940 109HP Engine Control ECU A6401501691 Automatic

Mercedes W245 OM640.940 109HP Engine Control ECU Automatic is a specialized module from the Electronic control modules and ECUs category, designed for precise management of the powertrain in Mercedes vehicles with diesel engines. The ECU works in conjunction with the fuel injection system and the automatic transmission, ensuring stable drive performance and consistent driving parameters.

Specifications and technical data

• SKU: A6401501691
• Mark: Mercedes (Genuine OE)
• Condition: Used
• OEM Part Number: A6401501691
• Substitutable numbers: A6401501691, A 640 150 16 91, 0281013965, 0 281 013 965
• Fuel type: Diesel
• Gearbox type: Automatic
• Part type: Transmission Control Module
• Category: ECUs & Computer Modules

Purpose and function of the ECU

The presented engine control unit is designed to work with the diesel powertrain in Mercedes B-Class W245 generation models, in the 109 HP version. The module is responsible for coordinating key engine operation processes, such as fuel dosage, boost pressure, and combustion parameter control, as well as communication with the automatic transmission. Thanks to dedicated software, the ECU is optimized for the characteristics of the OM640.940 engine and the specifics of the automatic transmission, which translates into smooth acceleration, predictable throttle response, and stable idle speed. Using an original ECU module allows for maintaining factory control logic and compatibility with other vehicle systems.

Powertrain compatibility

The ECU is designed to work with a diesel engine and an automatic transmission, which is important when selecting a replacement part. A properly selected ECU module ensures:

• consistent communication with the transmission control unit,
• correct handling of injection and torque maps,
• stable operation of onboard systems related to the powertrain. Selecting an ECU by OEM number or interchangeable numbers allows for verifying hardware and software compatibility with a specific vehicle configuration. In case of doubt, it is worth using the VIN number and service documentation to avoid communication issues within the vehicle's bus.

Performance characteristics and benefits of use

Choosing an original used engine control unit is a solution that allows for balancing reasonable repair costs with maintaining the factory electronics architecture. A module from the same series as the factory-installed component facilitates the adaptation process in the vehicle and minimizes the risk of software incompatibility. This is particularly important in the case of diesel units, where control precision has a direct impact on engine refinement, fuel consumption, and exhaust emissions. Electronic control modules and ECUs in Mercedes vehicles are an integral part of the CAN network, which is why using the correct engine control unit helps maintain proper cooperation with other modules, such as comfort, safety, or powertrain management systems. For workshops and users, this means easier diagnostics, predictable vehicle behavior, and reduced risk of communication errors.

Condition, origin, and installation aspects

The offered ECU is a used component, which in workshop practice often represents an optimal compromise between repair cost and maintaining the original vehicle specification. Before installation, a standard diagnostic procedure is recommended, including reading error codes, verifying communication with other modules, and – if necessary – matching the software to the specific car. In many cases, it may be necessary to perform adaptation procedures or coding using an appropriate diagnostic tester. Professional installation and configuration of the ECU allow for fully utilizing its capabilities and restoring the proper operation of the powertrain after the failure of the previous module.

Technical support and selecting the right ECU

If you want to deepen your knowledge about selecting used control modules, hardware and software compatibility principles, and safe installation of electronics from the secondary market, check out our guide: Used automotive electronics on board – why is it worth choosing second-hand ECU modules and sensors?. The article discusses, among other things, selection by OEM and VIN numbers, HW/SW compatibility issues, and practical examples of applications in repairs. If you are planning a comprehensive repair or upgrade of the engine area in your Mercedes and need other components from the same group, such as engine controllers, ECU modules, or electronic management units, check out the available parts in the Electronic control modules and ECUs Mercedes category.