What a multiplexer does
The multiplexer or vehicle communication interface (VCI) connects the diagnosis computer and software to the vehicle's diagnostic circuits. It selects or translates the supported communication channels. It is separate from the computer, the diagnostic application, the vehicle cable and any online service. A connector adapter alone is not a multiplexer.
Pictures of the interfaces
These manufacturer documents show the physical devices. C3, C4, C5 and C6 are workshop or seller labels and may be used inconsistently.
- Part D3 (often called C3): manufacturer photograph, page 1, item 1.
- SDconnect (often called C4): manufacturer photograph, page 1, item 2.
- XENTRY Connect (sometimes called C5): manufacturer photograph, page 3.
- XENTRY Diagnosis VCI (sometimes called C6): manufacturer photograph, page 1.
Image sources: Mercedes-Benz USA, STAR bulletin S-B-58.40/162 (2013), and Mercedes-Benz Canada, XENTRY Kit 3 Diagnosis VCI information (2017).
Names encountered in workshops
| Common label | Factory name and context | Important distinction |
|---|---|---|
| C3 | Often used for older STAR equipment and Part D3-type multiplexer setups. Mercedes' 2013 bulletin names the multiplexer Part D3 and lists Compact 3 w as a computer system. | Some C3 setups use an RS-232 to RS-485 converter between the computer and multiplexer. Cables and interface implementation vary. |
| C4 | Common trade label for SDconnect associated with STAR Diagnosis Compact 4; the two names identify different parts of the setup. | Mercedes documented both standard SDconnect and SDconnect DoIP. DoIP support must be verified on the actual unit and cable. |
| C5 | A seller may use this for XENTRY Connect or for other devices. | Genuine XENTRY Connect in Kit 2 ran the diagnostic desktop itself and was accessed remotely from the Tab 2 or a suitable PC. The label alone does not establish the device's origin or capability. |
| C6 | A seller may use this for the later XENTRY Diagnosis VCI, or for third-party devices. | Mercedes' product name is XENTRY Diagnosis VCI. Check the actual device, supported software and protocols rather than relying on C6 branding. |
C3, C4, C5 and C6 are useful search terms but are inconsistently applied in the resale market, including to third-party and replica hardware. A Compact 3 or Compact 4 is the diagnosis computer/system designation; it is not a guarantee that any particular multiplexer was supplied with it.
SDconnect and DoIP: a documented exception
Mercedes bulletin S-B-58.40/162 distinguishes standard SDconnect, with K-line and CAN, from SDconnect DoIP, which also has DoIP Ethernet. For the model 222 S-Class, that 2013 bulletin specifies Compact 4 with SDconnect DoIP, identified by the DoIP marking and the stated system-number threshold, or the specified XENTRY Kit. It also identifies a DoIP-compatible cable by yellow markings. These are period compatibility instructions for that application, not a promise that every present-day vehicle works with that device. The blanket statement that every C4/SDconnect lacks DoIP is incorrect.
Connections and choosing an interface
The Daimler SDconnect manual describes the interface connected to STAR by a dedicated cable, an ad-hoc WLAN link or the workshop WLAN. The newer XENTRY Diagnosis VCI uses a direct WLAN connection or USB in the Kit 3 guide. These computer-to-interface links are not the same as K-line, CAN or DoIP on the vehicle side.
Check the exact vehicle and module, supported software version, authorised functions, VCI model and firmware, vehicle-side protocols and correct cable. Mercedes' Kit 4 brochure lists the 16-pin OBD cable in the kit and older 8-, 14- and 38-pin adapters separately. The presence of an adapter does not itself establish coverage of all legacy lines or every HHT-WIN function.
Sources
Curated reference notes. Applicability follows the cited sources; hardware testing by this wiki is not implied.
- Mercedes-Benz STAR bulletin S-B-58.40/162: Multiplexer. Mercedes-Benz USA bulletin hosted by NHTSA; Part D3, SDconnect, SDconnect DoIP and model 222. Source revision 3 January 2013; accessed 2026-11-10.
- W220 S-Class Encyclopedia: STAR Diagnosis and C3 cables. Independent W220 community reference; example of an RS-232 to RS-485 PC-to-multiplexer cable. Source revision C3 cables and connectors section; accessed 2026-11-10.
- Mercedes-Benz: SDconnect manual. Daimler Star Diagnosis SDconnect manual, independent mirror; wired, ad-hoc and workshop WLAN modes. Source revision March 2011; accessed 2026-11-10.
- Mercedes-Benz XENTRY Kit 2 and XENTRY Connect user guide. Daimler user guide, independent mirror; XENTRY Connect, Tab 2 and remote diagnosis desktop. Source revision September 2014, version 1.3; accessed 2026-11-10.
- Mercedes-Benz XENTRY Diagnosis Kit 3 user guide. Daimler user guide, independent mirror; software location and VCI connection. Source revision March 2018; accessed 2026-11-10.
- Mercedes-Benz XENTRY Diagnosis VCI multiplexer. Mercedes-Benz Canada product information; Kit 3 interface and connection details. Source revision March 2017; accessed 2026-11-10.
- Mercedes-Benz XENTRY Diagnosis Kit 4 product brochure. Mercedes-Benz AG; 16-pin supplied cable and optional older adapters. Source revision August 2020; accessed 2026-11-10.