So I know I am a newbie and everyone hates newbies but, I have searched and really not found the info I need. I have a 1994 RRC LWB 4.2, just got it a few weeks ago and I have been fixing it up. Under my passenger seat is a box. This box I assume is the ECU as the vehicle runs perfectly. Above it however is a large plug, very similar to the plug that is in the ECU. A plug that I assume was plugged in to something at some time. Is this the plug for my on board diagnostics? I know I am missing something but to the best of my research thats my best guess. Could anyone confirm or deny this for me? This vehicle has had the coil swap so the only other thing I can think of is the Airbag system.