Volkswagen Caddy Mk5 AdBlue Tank Wiring Loom Harness 2.0 TDI 5R3971404

Volkswagen Caddy Mk5 AdBlue Tank Wiring Loom Harness 2.0 TDI is an original component from the Fuel tanks and filler pipes group, designed for the AdBlue dosing system in modern diesel units. The wiring harness ensures a stable electrical connection between the tank, sensors, and accessories, which translates into the proper operation of the exhaust emission reduction system in the Caddy Mk5 with a 2.0 TDI engine.

Specifications and technical data

• SKU: 5R3971404
• Mark: Volkswagen
• Condition: Used
• OEM Part Number: 5R3971404
• Substitutable numbers: 5R3971404, 5R3 971 404
• Part type: Fuel Tank
• Category: Fuel Tanks & Filler Necks

Purpose and function in the AdBlue system

The presented AdBlue tank wiring harness is dedicated to the fifth-generation Volkswagen Caddy model with a 2.0 TDI engine, where it is responsible for transmitting signals and power between the tank, level sensors, temperature sensors, and system actuators. A properly functioning harness is crucial for:

• maintaining correct communication with the engine control module,
• precise dosing of the AdBlue solution into the exhaust system,
• preventing diagnostic errors related to the SCR system,
• stable vehicle operation in compliance with emission standards.

Thanks to the use of an original cable and connector design, the harness maintains factory electrical characteristics, which facilitates diagnostics and compatibility with the factory controller software.

Construction, compatibility, and installation

The AdBlue tank wiring harness has been designed specifically for the Caddy Mk5 chassis geometry, which allows the cables to be routed through the original mounting points. Properly selected cable lengths and factory connectors minimize the risk of tension, abrasion, and electrical leaks.

During installation, it is worth paying attention to:

• routing the cables in accordance with factory brackets and covers,
• correctly snapping the connectors into the tank and accessory sockets,
• visual inspection of the insulation for mechanical damage,
• performing a diagnostic test after installation to verify communication with the sensors.

This approach shortens service time and reduces the risk of repeated interference with the AdBlue system after replacing the harness.

Benefits of using an original Volkswagen harness

Using an original AdBlue tank wiring harness in a Volkswagen Caddy Mk5 provides a number of practical service and operational benefits:

• Factory fit – compatibility with the body geometry and the layout of AdBlue system components, without the need for modifications.
• Stable electrical parameters – proper resistance and cable shielding, which reduces signal interference from sensors.
• Easier diagnostics – maintaining the original installation diagram facilitates work with service documentation and diagnostic testers.
• SCR system safety – correct power supply and reading of parameters from sensors reduces the risk of the engine entering emergency mode.

For workshops and fleet users, this means more predictable service and a lower risk of vehicle returns due to AdBlue system problems.

Condition, verification, and service application

The item comes from dismantling and is offered as a used part, which allows for optimizing repair costs while maintaining the manufacturer's original specifications. Before re-installation, it is recommended to:

• check circuit continuity with a meter,
• inspect the condition of the connectors for corrosion and looseness,
• assess the flexibility of the insulation at the bends.

A harness prepared in this way can be successfully used both when replacing a damaged section of the installation and during a comprehensive repair of the AdBlue system after a collision or corrosion of chassis components.

If you are planning a comprehensive repair or upgrade of the fuel-dosing system area in your Volkswagen and need other components from the same group, such as filler pipes, tank mounting elements, or additional installation sections, check the available parts in the Volkswagen fuel tanks and filler pipes category.

Technical support and knowledge about the fuel system

To better plan diagnostics and the selection of components related to the tank and installation, it is worth using educational materials describing the construction and servicing of the fuel supply system. A detailed discussion of operating principles, diagnostic methods, and part selection by identification numbers can be found in the article Fuel system – injectors, pumps, and fuel tank: maintenance and regeneration, which will help organize your knowledge and reduce the risk of errors during repair.