BMW E90 E92 E93 M3 Engine S65 420HP ECU Kit DME 7841981 + CAS3 + 2 Keys

BMW E90 E92 E93 M3 Engine S65 420HP ECU Kit DME + CAS3 + 2 Keys is a complete engine control set designed for the sporty BMW M3 3-series models equipped with the 420 HP S65 engine. The set includes the DME engine control unit, the CAS3 module, and two keys, providing a cohesive electronic package that is easy to match to a specific vehicle. This solution is particularly attractive for engine swaps, drivetrain conversions, or professional control system repairs.

Specifications and technical data

• SKU: 7841981-1
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 7841981
• Substitutable numbers: 12147848125, 7848125, 12147842487 12147841981 12147841364, 12147841365 12147846903 12147842404, 12147842403 12147840872 12147841102, 12147846409 12147846055 12147842905, 12147841982 12147845558 12147842488, 12147840873 12147842191 12147842192, 7842487 7841
• Category: ECUs & Computer Modules

Application and function of the ECU DME + CAS3 kit

The presented set belongs to the Electronic control modules and ECUs category and is responsible for the precise management of the V8 S65 engine in the BMW M3 E90, E92, and E93. The DME controller manages parameters such as fuel dosage, ignition, and auxiliary equipment operation, while the CAS3 module handles start authorization and communication with the keys. Thanks to the inclusion of two keys, the entire package forms a coherent immobilizer and control system, which significantly simplifies installation in a vehicle after a swap or when replacing a faulty controller.

Benefits of installing the complete DME + CAS3 + 2 keys set

Using a complete control set in a BMW M3 with an S65 engine offers a number of practical technical benefits:

• maintaining compatibility between the engine controller and the CAS3 module,
• minimizing issues with immobilizer matching and key coding,
• facilitating the startup of the S65 unit after a conversion or drivetrain replacement,
• the ability to use the set for swap projects within the 3-series platform.

For workshops specializing in BMW M3s and for advanced enthusiasts, this package serves as a practical foundation for further engine electronics configuration, without the need to source components from multiple suppliers.

Product characteristics and condition

The offered set is a removed part and has the status of a used electronic module, which is a typical solution for repairing advanced control systems in M-class vehicles. In practice, this allows for an economical restoration of the engine control system's functionality while maintaining the original BMW architecture. The set is particularly useful in situations where the factory DME controller has been damaged or there are issues with the CAS3 module preventing the engine from starting.

Professional use in BMW service and tuning projects

The complete DME + CAS3 + 2 keys package fits well into the needs of service centers handling M3 E90/E92/E93 models, as well as tuning projects and track car reconstructions. It facilitates:

• restoring proper communication within the vehicle's electronic network,
• performing repairs after engine electronics failure,
• building project vehicles based on the 420 HP S65 unit.

By maintaining the original control architecture, further specialized programming and tuning by expert workshops is possible, making this set a solid base for advanced modifications.

More about BMW electronics and best practices for used parts

If you want to better understand how to safely use used electronic modules, engine controllers, and comfort systems in BMW 3 and 5 series, it is worth checking out the guide on our blog: Driving pleasure for years – how to take care of iDrive systems and electronic modules in BMW 3 and 5 series models. You will find practical tips on diagnostics, installation, and verification of removed parts.

If you are planning a comprehensive repair or upgrade of the engine area in your BMW and need other components from the same group, such as engine controllers, comfort modules, or drivetrain management units, check out the available parts in the BMW electronic control modules and ECUs category.