Vehicle Control Modules – BCM, BSI, BSM, UCH, CAS and SAM

Vehicle Control Modules – BCM, BSI, BSM, UCH, CAS, SAM and Comfort Units

Modern vehicles use many electronic modules to control body functions, power distribution, access systems, lighting, comfort equipment and communication between different vehicle systems.

Depending on the manufacturer, these electronic units may be described as BCM, BSI, BSM, UCH, USM, CAS, SAM, comfort control modules, central electronic modules or simply vehicle control units.

Although many of these modules perform related functions, the terminology and exact responsibilities differ between vehicle manufacturers. For this reason, the safest way to identify a replacement is by the complete part number.

What is a Body Control Module – BCM?

A BCM – Body Control Module manages selected electrical and body functions in the vehicle.

Depending on the vehicle architecture, these can include:

• central locking,
• interior and exterior lighting,
• electric windows,
• wipers and washers,
• alarm functions,
• door electronics,
• power distribution,
• communication with other control units.

The exact BCM functions vary considerably between manufacturers and vehicle generations.

BSI modules – Peugeot, Citroën, Fiat and other applications

BSI is a term commonly associated with central body-electronics modules in selected vehicle systems. Depending on the application, the BSI can manage multiple comfort, electrical and communication functions.

A BSI may contain vehicle-specific configuration or security information. For this reason, replacement requirements should always be checked for the exact vehicle and module.

One example from the catalogue is the Fiat / Iveco Daily BSI module 69500005 / 69500042.

Important references associated with this family include:

• 69500005,
• 69500042,
• 503440070109,
• 503440070119,
• NBCS20A.00.

The presence of several references on one module is a good example of why all numbers on the original label should be compared.

BCM, BSI and BSM – what is the difference?

These abbreviations should not automatically be treated as names for the same component.

• BCM generally means Body Control Module.
• BSI is used in selected vehicle architectures for a central body and electrical systems interface.
• BSM is commonly associated with an engine-bay power distribution and switching module in selected PSA applications.

Their exact roles depend on the manufacturer and vehicle generation.

Renault UCH and USM modules

Renault uses several module designations within its vehicle electrical architecture.

UCH commonly refers to a cabin or body electronics control module, while USM can be associated with electrical power distribution and protection functions depending on the model.

A current example is the Renault USM module 284B69009R.

The key reference is:

• 284B69009R.

When looking for another Renault UCH or USM module, compare the complete Renault part number rather than relying only on the UCH or USM abbreviation.

Ford comfort control modules

Comfort modules can control functions associated with vehicle access, central locking, windows and other body electronics.

One example is the Ford comfort control module 1S7T15K600FD / Siemens 5WK48730F.

Important references:

• 1S7T15K600FD,
• 5WK48730F.

This example combines a Ford engineering number with a Siemens electronics reference.

Both numbers are useful when identifying the correct replacement.

Siemens and Siemens VDO vehicle modules

Siemens and Siemens VDO manufactured many different types of vehicle electronics, including comfort, access, immobiliser and body-control modules.

Common Siemens references can begin with:

• 5WK...,
• A2C...,
• other manufacturer-specific number families.

The complete Siemens number should be checked together with the vehicle OEM reference.

CAS modules – access and starting systems

CAS is commonly associated with BMW vehicle-access and starting-authorisation systems.

Depending on the generation, a CAS module can be involved in:

• key recognition,
• vehicle access,
• starting authorisation,
• communication with the engine management system,
• vehicle-specific security data.

Used CAS modules can contain data from the previous vehicle, so replacement should not automatically be treated as a simple Plug & Play operation.

SAM modules – Mercedes-Benz electronics

SAM – Signal Acquisition and Actuation Module is a designation used in Mercedes-Benz electrical systems.

Depending on its location and vehicle generation, a SAM module may manage or distribute signals and power for various electrical components.

The Auto24Parts catalogue also includes Mercedes electronic modules such as the Mercedes-Benz control module 0335456032.

For Mercedes electronics, the complete A-number or other OEM reference should always be checked before purchasing.

Audi MMI and multimedia control modules

The Vehicle Control Modules category can also contain electronic units outside the traditional BCM / BSI group.

An example is the Audi MMI Becker control module 4E0035729A.

The part number can be written as:

• 4E0035729A,
• 4E0 035 729 A.

This module belongs to Audi's multimedia electronics rather than being a traditional body-control module, which is another reason why the broad category name Vehicle Control Modules is more suitable than simply “BCM Modules”.

Immobiliser and security-related modules

Some vehicle electronic modules form part of the immobiliser, access or starting-authorisation system.

These modules can contain vehicle-specific security information and may need to communicate correctly with:

• engine ECU,
• keys or transponders,
• body control module,
• instrument cluster,
• other security-related electronics.

A used immobiliser-related module may therefore require adaptation, synchronisation or data transfer depending on the vehicle.

How to choose the correct vehicle control module

The most important step is to compare the label on the original module.

Check:

• complete OEM number,
• electronics manufacturer number,
• all suffix letters and digits,
• hardware and software references where available,
• module family such as BCM, BSI, UCH, USM or CAS,
• vehicle model and production year as supporting information.

Do not choose a module only by its housing, connector layout or vehicle model.

Why suffix letters are important

Vehicle module numbers often contain final letters that identify a specific hardware or software version.

For example:

• 1S7T15K600FD,
• 4E0035729A,
• other OEM numbers ending in A, B, C, AA, AB or similar suffixes.

A shared base number does not automatically mean that different suffix versions are interchangeable.

Common symptoms of a body or comfort module fault

Possible symptoms can include:

• central locking not operating correctly,
• electric windows not responding,
• lighting problems,
• wipers operating incorrectly,
• intermittent electrical faults,
• alarm problems,
• no communication with a module,
• vehicle not recognising a key,
• multiple electrical functions failing at the same time.

These symptoms do not automatically confirm that the module itself is faulty.

No communication with a vehicle module

If diagnostic equipment cannot communicate with a BCM, BSI, UCH or another control unit, check:

• power supply,
• ground connections,
• fuses and relays,
• connector condition,
• damaged or corroded pins,
• CAN or other communication wiring,
• water ingress or corrosion.

Loss of communication may be caused by the controller itself or by the vehicle wiring and power supply.

Water damage and body control modules

Body and comfort modules are often installed inside the passenger compartment, footwell, luggage compartment or electrical boxes.

Depending on the vehicle, water ingress can cause:

• connector corrosion,
• damaged circuit boards,
• intermittent electrical faults,
• short circuits,
• communication problems.

Before replacing a water-damaged module, the source of the leak should also be repaired.

Does a used BCM, BSI or comfort module require programming?

There is no single rule for every vehicle control module.

Depending on the system, replacement may involve:

• coding,
• vehicle configuration,
• adaptation,
• security synchronisation,
• VIN or configuration transfer,
• data transfer from the original module,
• another manufacturer-specific procedure.

Other modules may require little or no additional configuration.

Programming requirements should therefore be checked for the exact module and vehicle.

Can a vehicle control module be cloned?

For selected electronic modules, it may be possible to transfer required data from the original unit to a compatible replacement.

The possibility depends on:

• module type,
• electronics design,
• availability of the required data,
• condition of the original unit.

If the original controller cannot be read, another adaptation or programming procedure may be required.

Selected vehicle control modules

The catalogue includes different types of electronic units, for example the Renault USM 284B69009R, Ford / Siemens comfort module 1S7T15K600FD / 5WK48730F, Fiat / Iveco BSI 69500005 / 69500042, Audi MMI Becker 4E0035729A and Mercedes-Benz module 0335456032.

How to search for a vehicle control module by part number

Useful search combinations include:

• Renault USM 284B69009R,
• Ford comfort module 1S7T15K600FD 5WK48730F,
• Fiat Iveco BSI 69500005 69500042,
• Fiat Iveco BSI 503440070109,
• Audi MMI module 4E0035729A,
• Mercedes control module 0335456032,
• BCM module OEM number,
• BSI module part number.

Searching by complete numbers normally gives more accurate results than searching only by the name of the vehicle or module type.

Related electronic car parts

• Electronic Car Parts
• Engine Control Units – ECU
• ABS / ESP / ASR Control Units
• Automatic Transmission Control Units
• Instrument Clusters
• Siemens Automotive Electronics
• Magneti Marelli Modules

How to confirm compatibility before ordering

If you are unsure which module is correct, contact Auto24Parts.

For compatibility verification, send:

• a clear photo of the complete original module label,
• all OEM numbers,
• electronics manufacturer number,
• vehicle make and model,
• production year,
• engine version if relevant,
• a short description of the module or fault.

The complete identification numbers from the original unit are the safest basis for choosing a replacement module.

Ordering, Payment, Delivery and Returns

Ordering information is available in our How to Buy guide. Payment options are listed under Secure Payment Methods, while shipping information can be found on the Shipping & Delivery page.

Current information about returns, complaints and warranty is available under Returns, Warranty & Complaints.

FAQ – Vehicle Control Modules