Nov 14, 2019 - 10:44 AM
The "standard" Diagnostic Plugs are a Round Deutsch plug with 6 or 9 Pin Postions. There are Diagnostic Connectors in the Engine Compartment and "upfront" near the Steering Column generally with a protective cap. The Round Deutsch plugs were chosen at the time the Electronic Engine Standard was developed, so you will always have one of these Plugs when you have an Electronic Diesel Engine. Not all of the Positions will have Terminals (the Metal Contacts). Typically, the 6 Pin Plugs have 4 Terminals, the 9 Pin Plugs have 4 Terminals and with later coaches they have 7 Terminals.