BMW E46 M3 S54 343HP ECU Engine Control Unit Kit DDE 7835564 CAS3 + Key Manual

BMW E46 M3 S54 343HP ECU Engine Control Unit Kit CAS3 + Key Manual is a complete engine control kit designed for the 343HP S54 performance engine, paired with a manual transmission. The kit includes the ECU, the CAS3 module, and a matched key, which facilitates the transfer of the complete electronic system between vehicles. This solution is particularly attractive for engine swaps, repairs following electronic damage, or restoring the full functionality of the factory powertrain.

Specifications and technical data

• SKU: 7835564-1
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 7835564
• Substitutable numbers: 12147837805, 7837805, 12147842355, 7842355, 12147837806, 7837806, 12147836454, 7836454, 12147835564, 7835564, 12147836455, 7836455, 12147842356, 7842356, 5WK9326, 61356905666, 6905666
• Gearbox type: Manual
• Category: ECUs & Computer Modules

Purpose and function of the engine control unit kit

The presented ECU kit with the CAS3 module and key is designed to work with the S54 engine in the BMW E46 M3 model, ensuring proper engine management and start authorization. Combining the engine control unit with the immobilizer module and a matched key allows for maintaining system security integrity, which reduces the need for additional programming and minimizes the risk of vehicle starting issues.

Thanks to the configuration for a manual transmission, the kit is suitable for cars with a classic mechanical gear shifting system, which is important both for repairs and for conversions from other powertrain versions.

Benefits of using the complete ECU + CAS3 + key kit

Using a complete engine control kit with the CAS3 module and key provides a number of practical benefits in service and tuning:

• a consistent engine and security electronic system, reducing module synchronization issues,
• easier installation compared to sourcing individual components from different vehicles,
• the ability to use it in S54 engine swap projects for other BMW 3 Series chassis,
• maintaining engine performance characteristics consistent with the factory M3 configuration.

For workshops specializing in the BMW brand and for advanced enthusiasts, such a kit provides a practical base for rebuilding or upgrading the powertrain without the need for deep interference in the software of multiple modules.

Integration with vehicle electronics and service applications

As an element of the Electronic control modules and ECUs category, this ECU kit with CAS3 and key works with other vehicle electronic systems, such as comfort modules, safety systems, or OBD diagnostic systems. A properly selected and configured kit allows for:

• restoring full engine functionality after the failure of the original controller,
• resolving issues with the immobilizer and key authorization,
• stable cooperation with factory BMW diagnostic systems,
• maintaining correct ignition and injection maps for the S54 unit.

This approach is particularly important in higher-power cars, where precise engine control affects component durability and performance repeatability on the track and in daily use.

Product characteristics and condition

The offered kit comes from dismantling, which allows for an economical restoration of the original engine control system in the BMW E46 M3. The used nature of the parts makes it a cost-effective solution while maintaining parameters consistent with the manufacturer's factory specifications. For many renovation and track projects, this is a reasonable compromise between price and functionality, especially when the priority is to maintain original BMW electronics.

Related modules and technical knowledge

When working with BMW 3 and 5 Series electronics – including iDrive systems, FRM modules, or engine controllers – it is worth using proven service procedures and the experience of other users. Practical tips regarding repairs and selecting parts from dismantling can be found in the article: Driving pleasure for years – how to take care of iDrive systems and electronic modules in BMW 3 and 5 Series models.

If you want to analyze more broadly when it is worth using used engine controllers and other electronic modules, the following guide may also be helpful: The second life of electronics – when is it worth choosing used engine controllers, comfort modules, and parking sensors?.

If you are planning a comprehensive repair or upgrade of the engine area in your BMW and need other elements from the same group, such as engine controllers, engine management modules, or auxiliary controllers, check the available parts in the BMW Electronic control modules and ECUs category.