Honda OBD2 Port - technical details

[SCOPESYS]

I am trying to find out some more detailed information about the OBD2 Port as used in Gen X Honda vehicles.
In Particular, the Honda specific pins on the connector, and what that functionality is.

Putting aside any Legal/Law issues with touching the OBD2 Port (at least here in the USA), I would like to understand the technical side of things, in particular with respect to it's use by Honda Service Techs, and State Emissions Testing facilities. The Honda specific pins(s) and their function are of particular interest, as, at first sight, they appear to be associated with the Vehicles Alarm system, and the programming of the security system.

BTW: I am NOT interested in being told that I don't need to know about this. I am just looking for a technical discussion, WITHOUT all the BS of why I cannot know about this subject.

Hopefully there are some in this forum, who know about this, and are willing to share their knowledge.

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[calonzo]

There should be plenty of information out there. Here are some links I found:

http://www.evoscan.com/technical-vehicle-manuals/107-honda-obd-ii?format=pdf
http://pinoutguide.com/CarElectronics/honda_obd_2_pinout.shtml

 

[SCOPESYS]

There should be plenty of information out there. Here are some links I found:

http://www.evoscan.com/technical-vehicle-manuals/107-honda-obd-ii?format=pdf
http://pinoutguide.com/CarElectronics/honda_obd_2_pinout.shtml

Thanks -- thats is what I have so far already.

Pin

Signal Description

4 CGND Chassis ground
5 SGND Signal ground
6 CAN High J-2284
7 K-LINE (ISO 9141-2 and ISO/DIS 14230-4)
9 SCS SCS (Service Check System) - diagnostic codes
12 Programming out
13 or 14? Input/Output for VTM-4 and immobilizer control
14 CAN Low J-2284 (WEN)
15 ISO 9141-2 L-LINE (ISO 9141-2 and ISO/DIS 14230-4)
16 +12v Battery power (unswitched)

My primary interest is with pins 12, 13 and 14, in particular 13 & 14.

Apart from re-programming the VTM-4 and Immobilizer Control, I cannot see why anyone should NEED to have access to these, except someone trying to alter the Immobilizer, or program a new key etc .. ie The Dealer.

ie NOT a car thief, trying to start my car, by re-programming the system to their key etc.

For Example, I cannot see why that access NEEDS to be available to say. "State Vehicle Emissions Inspection" etc.

You can probably see where I am going with this -- I would like to LOCK OUT those connections with some hidden lockable control, but want to make sure that I am not preventing authorized access by the Dealer to Diagnose my car, or the State Emissions Station to test my vehicle.

I can also see that others might also be interested making any WRITE function, Lockable -- if nothing else to prevent Dealers from doing any updates or changes that you do not approve of.

For the time being, can we just say I am interested in this for EDUCATIONAL purposes .. I really do NOT want to go into a long Legal Debate about what a Car owner can and cannot do to their OBD2 Port. That could be another Thread please !!

In my ideal world, I would like to able to periodically Scan my car Myself, and know of any errors etc BEFORE I take it to the Dealer for Diagnosis and repair.
Then, if there are any Code issues, I have a record of them, and can request that the dealer only works to correct those errors, and establish an understanding of what I expect the Dealer to do, and more importantly NOT do, before I entrust them to "let loose" on my car.

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