Results 1 to 6 of 6

Thread: J1850 PWM specs

  1. #1
    Newbie
    Join Date
    Oct 2008
    Posts
    8

    J1850 PWM specs

    I am trying to build my own code reader using a PIC interfaced to a laptop for J1850 PWM to use with a Ford but having a hard time finding information about the protocol. Are there any resources on the web that explain it? I have various links bookmarked that explain the general workings of it but nothing really detailed.

    Yes, I realize that I have to pay for the SAE documents but I am a poor college student doing this for a school project so I can't afford it. Any help is appreciated.

  2. #2
    Newbie
    Join Date
    Oct 2008
    Posts
    8
    I think I figured out most of the protocol but have a couple of questions still. Is the CRC byte always 0x0a?

    I am going by examples here, Ford J1850 PWM

  3. #3
    Variable Bitrate
    Join Date
    Oct 2008
    Posts
    376

  4. #4
    Low Bitrate sinclairvital's Avatar
    Join Date
    Jun 2005
    Posts
    61
    Some timing information here:
    http://www.kbmsystems.net/SAEJ1850.htm

  5. #5
    Newbie
    Join Date
    Oct 2008
    Posts
    8
    Thanks for the links. I was able to get a hold of the actual SAE documentation which I found rather confusing.

    Never the less I am now able to receive data from the ECM. My question now is about IFR. I think I am missing something.

    Here is what's happening right now. I am sending

    SOF 0x61 0x6A 0xF1 0x01 0x00 0x0A EOF

    The reply I get back is

    SOF 0x41 0x6B 0x10 and either nothing else or a few 0x00 bytes

    What am I missing? Am I suppose to send something back after I get 0x10 byte?

  6. #6
    Newbie
    Join Date
    Oct 2008
    Posts
    8
    Looks like I am doing something incorrectly. The response that I receive back is on the line constantly, regardless if I send anything to the ECU or not.

    I guess my question would be, at what point should I be requesting data?

Similar Threads

  1. Ford J1850 PWM
    By plisskin in forum Engine Management, OBD-II, Engine Diagnostics, etc.
    Replies: 23
    Last Post: 12-23-2010, 02:33 PM
  2. Question about PWM
    By catatung in forum Hardware Development
    Replies: 2
    Last Post: 09-03-2008, 02:04 PM
  3. My carpc specs. Are they alright??
    By ironic in forum General MP3Car Discussion
    Replies: 0
    Last Post: 12-12-2005, 04:16 PM
  4. PWM j1850 response 0x10
    By Juan Wortley in forum Engine Management, OBD-II, Engine Diagnostics, etc.
    Replies: 0
    Last Post: 11-04-2005, 03:56 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •