Mercedes W251 R320 CDI OM642.950 224HP Engine Module ECU A6421506891 Automatic

Mercedes W251 R320 CDI OM642.950 224HP Engine Module ECU is a factory-original electronic control unit designed for the diesel powertrain of the R-Class model. As a component from the Electronic control modules and controllers group, it is responsible for the precise management of the engine's operation, ensuring stable power characteristics and proper integration with other vehicle systems. This is an ideal solution for users looking to restore full engine functionality while maintaining the original Mercedes electronic architecture.

Specifications and technical data

• SKU: A6421506891
• Mark: Mercedes (Genuine OE)
• Condition: Used
• OEM Part Number: A6421506891
• Substitutable numbers: A6421506891, A 642 150 68 91
• Gearbox type: Automatic
• Part type: Engine Control Unit (ECU)
• Category: ECUs & Computer Modules

Purpose and function of the controller

The presented engine control unit is dedicated to the powertrain featuring the OM642.950 engine with 224 HP in the Mercedes W251 R320 CDI model. The ECU manages key engine operating parameters, such as fuel injection quantity, boost pressure, starting strategy, and load response, while communicating with sensors and other vehicle modules. This ensures the maintenance of proper dynamics, smooth operation, and compliance with factory control maps.

Integration with the automatic transmission

The ECU has been configured to work with an automatic transmission, which is essential for proper communication within the vehicle's network and smooth gear shifting. Proper matching of the controller to the transmission type ensures:

• correct synchronization of torque with gear-shifting logic,
• stable operation of driver assistance systems,
• preservation of factory driving comfort parameters.

As a result, this engine control unit can be used as a component to restore full powertrain functionality following the failure of the original controller.

Characteristics and practical application

As a part from the Electronic control modules and controllers group, this ECU is designed for installation in place of the factory controller, maintaining the original wiring architecture. In practice, this means it can be used for:

• vehicle repair following engine electronics failure,
• restoring factory configuration after unsuccessful modifications,
• comparative diagnostics in cases of hard-to-locate faults.

A used controller helps reduce service costs while maintaining consistency with the safety and comfort systems characteristic of the Mercedes brand.

Why consider a used engine control unit

Choosing a used ECU for a Mercedes W251 R320 CDI is often a reasonable compromise between costs and maintaining the vehicle's original specifications. A properly selected controller:

• enables the restoration of engine performance without interfering with the wiring harness,
• ensures compatibility with factory diagnostic systems,
• allows for maintaining software consistency across the vehicle's entire electronic system.

If you want to better understand when choosing a used module is cost-effective and what to look for when selecting one, check out our guide: A second life for electronics – when is it worth choosing used engine controllers, comfort modules, and parking sensors?.

Expanding the control system in your Mercedes

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 additional controllers, engine management modules, or systems that work with the ECU, check out the available parts in the Electronic control modules and controllers Mercedes category.