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Thread: Help Determine Vehicle OBD Protocol

  1. #1
    Newbie
    Join Date
    Aug 2009
    Posts
    1

    Help Determine Vehicle OBD Protocol

    Hello,

    New to the forum, but have visited the site many times. Great info and I appreciate everyones efforts. Wish I had signed up sooner so as not to be asking for help from my first post, but I'm really in a pickle trying to figure out what protocol my truck uses.

    The truck is a 2006 Nissan Titan King-cab LE, 4x4 5.6L

    The J-1962 (OBD-II connector) has the following pins occupied:

    4,5,6,7,8,14,16

    ISO-9141-2 & ISO-14230 are said to use pin 7 & sometimes pin 15. Pin 7 is in use, while pin 15 is Not.

    CAN is said to use pins 6 & 14. Both are in use.

    So there is my problem. Everything I've found on-line to help figure out what protocol is in use, describes looking at what pins are in use. But with my truck it could be either ISO-9141-2/14230 or CAN.

    I've called a couple of Nissan dealerships and they were no help. I've also been in contact with a company that manufactures obd diagnostic products and their trying to help as well. I'm at a loss. Not sure what else I can do to determine what protocol is in use.

    I need to know this because the ISO protocols are too slow for the device I'm looking to buy. Its expensive and has a restocking fee, so I want to make sure the truck is using CAN before I buy.

    I have read the volts while key is in the off position and they are:
    (meter negative to vehicle ground)

    CAN Pins 6 & 14 are + .738Vdc
    ISO Pin 7 is + 2.85Vdc

    Not sure if that helps, but figure I'd post.

    Any help in figuring out what protocol is used would be greatly appreciated.
    Thanks

  2. #2
    Variable Bitrate
    Join Date
    Oct 2008
    Posts
    376
    Find somebody with an OBD2 scanner and read out the ecu.
    The scanner will tell you which protocol is used.

  3. #3
    Low Bitrate
    Join Date
    Sep 2008
    Posts
    99
    Unfortunately there that year is right in the middle of when most manufacturers were transitioning from slower protocols to CAN. One point I have found fairly reliable is to look at the year the vehicle undergoes a significant interior or exterior change. That is usually when manufacturers begin to implement the CAN protocol. For example the 2004 ford F150 is CAN and 04 was the first year for that body style after the 97-03 body. The Dodge minivan finally moved to CAN for the 08 model year after having the same body style for over 10 years. I was not able to find anything noticeable for the Titan, but if you are an enthusiast, you may be able to point out some more subtle changes that may help us guess when Nissan went to CAN.

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