BMW 1 3 Series F20 F30 LCI M140i 340i Engine Gearbox Module Wiring Loom Harness

The BMW F20 F30 LCI M140i 340i Engine Harness is an original part from the Cables, Harnesses, and Connectors group, designed for use in modern BMW F-series power units with the B58 engine. It enables proper connection of sensors, ancillaries, and the engine control unit, ensuring stable electrical communication and predictable powertrain operation.

Specifications and technical data

• SKU: 8631672
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 8631672
• Substitutable numbers: 12538631672, 8631672, F21 F31 LCI B58, Set, EM
• Category: Wiring Harnesses, Cables & Connectors

Intended Use and Function of the Engine Harness

The presented harness is dedicated to facelifted (LCI) BMW F-series models, specifically the M140i and 340i versions with the B58 engine. It is responsible for distributing power and control signals between the engine control unit, sensors, actuators, and the powertrain's ancillaries. Thanks to the factory wiring and connector architecture, the correct installation topology is maintained, which reduces the risk of interference and communication errors in the vehicle's bus systems.

Construction, Connectors, and Compatibility

This harness belongs to the Cables, Harnesses, and Connectors group, meaning it includes a complete set of wires with appropriately selected terminals and connectors for specific engine components. The connectors used are factory-matched to BMW components, facilitating plug-and-play installation within the engine bay. The wire construction is designed to withstand elevated temperatures and environments exposed to vibrations, which is crucial for the long-term reliability of the electrical system.

By maintaining the original harness geometry, it is possible to route the wires correctly in the factory mounting points, without the need for modifications or shortening of sections. This is important both from a safety perspective (no rubbing against moving parts) and for subsequent serviceability.

Benefits of Using an Original BMW Harness

Using an original BMW engine harness translates into several key technical benefits:

• maintaining full compatibility with the factory engine control unit and ancillaries,
• correct assignment of connectors to sensors and actuators,
• appropriately selected wire gauges and insulation adapted to operating conditions in the engine bay,
• reducing the risk of installation errors typical for modified or universal harnesses.

For users planning to repair or swap a B58 unit in F20/F30 LCI models, using such a harness allows for maintaining installation consistency with the factory service documentation, which facilitates diagnostics and subsequent workshop tasks.

Condition, Verification, and Service Application

The offered BMW engine harness comes from the secondary market, allowing for economical vehicle repair while maintaining the original manufacturer's specifications. This type of part is particularly useful for:

• repairs after mechanical or thermal damage to the engine bay installation,
• engine unit swaps within the same model generation,
• resolving issues with unstable engine operation resulting from damaged wires or connectors.

By preserving the factory wiring and connector layout, the harness provides a solid foundation for restoring correct powertrain operation without the need to interfere with the vehicle's original electrical architecture.

Expanding the Installation within the BMW Engine Area

If you are planning a comprehensive repair or upgrade of the engine area in your BMW and need other parts from the same group, such as additional ancillary harnesses, wire sections, or service connectors, check the available parts in the BMW Cables, Harnesses, and Connectors category.

To better select a used engine harness for your specific car configuration and avoid compatibility issues, it's worth seeking expert advice – detailed tips can be found in the article No More Wrong Purchases! How to Professionally Select Used Car Parts.