A faulty “Diagnostic Port” fuse can prevent a scan tool from connecting to a 2017 Mercedes-Benz C300. This article details how a missing fuse was identified and replaced, resolving the issue. The fuse box diagram, often overlooked, is located inside the fuse panel on the driver’s side of the dashboard, accessible by removing the end cap. Initially, searching for terms like “ECU Port” or “OBD Port” on the diagram proved fruitless. A thorough review revealed the correct listing: “Diagnostic Port,” with its corresponding bay number (62) and amperage (15 AMPS). Surprisingly, the fuse was missing from the designated bay. The vehicle, purchased nearly new and consistently serviced at a Mercedes-Benz dealership, had its alternator replaced at a local shop the previous year. It’s suspected the fuse might have been removed during that repair. Installing a new 15 AMP fuse in bay 62 immediately restored functionality to the diagnostic port. This allowed for successful connection with a scan tool, enabling vehicle diagnostics and smog check completion, despite a pending code related to the previous alternator issue. While the reason for the missing fuse remains unclear, this experience highlights the importance of checking this often-overlooked component when a scan tool connection problem arises.
A careful examination of the fuse box diagram is crucial for troubleshooting.
The “Diagnostic Port” fuse, often listed separately from terms like “ECU Port” or “OBD port,” is essential for scan tool communication.
