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Thread: Silent CAN on jeep Patriot?!?

  1. #1
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    Silent CAN on jeep Patriot?!?

    Hi, I just connected a CAN sniffer on the DLC connector on a '09 Jeep Patriot. The link is active but it is completely silent.

    I think that this vehicule has a gateway and only diagnostics request end up on this CANbus segment. Can someone confirm?

    Appart from the "regular" OBD requests, I need to read if the break pedal is pressed and the gear selector position. This was quite easy to do on a Ford using mode 22. Does anyone know if this info is available in some enheanced OBD mode? If not, this must be present on the RAW CAN, but I don't want to start stripping and soldering the 500kbs CAN wires that connecte the engine ECU and all other critical parts of the car... Also, how will the car react if I passively sniff this bus but also send some OBD request on the link that is not meant for it...

    Thanks for your help!
    Frederick

  2. #2
    Constant Bitrate joeyoravec's Avatar
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    Quote Originally Posted by fprigge View Post
    Hi, I just connected a CAN sniffer on the DLC connector on a '09 Jeep Patriot. The link is active but it is completely silent.

    I think that this vehicule has a gateway and only diagnostics request end up on this CANbus segment. Can someone confirm?
    Yes probably. Chrysler almost always designs their vehicle with a gateway. That way the external scantool is less likely to take down the entire powertrain network.

    Quote Originally Posted by fprigge View Post
    Does anyone know if this info is available in some enheanced OBD mode?
    There almost always is, but Chrysler reassigns PIDs for almost every car so I don't know it off hand. And you'd have to know a lot more about the vehicle to know which of those bazillion lists applies for your vehicle.

    Quote Originally Posted by fprigge View Post
    Also, how will the car react if I passively sniff this bus but also send some OBD request on the link that is not meant for it...
    Possibly badly. Don't recommend it while driving the car.

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    Hi Joeyoravec, thanks for the quick reply.

    To your knowledge, does chrysler use mode 22 for their enhanced PIDs?

    My plan is to scan (and log) all possible PIDs in mode 22 (or whatever you recommend) with the key in the "run" position with engine stopped. Then re-do with break pedal pressed and then re-do with shifter in gear. After that I do a highlight difference in the dump and investigate the PIDs that have changed. This technique has proven to be successful with my Fords up to now...

  4. #4
    Constant Bitrate joeyoravec's Avatar
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    Quote Originally Posted by fprigge View Post
    ]To your knowledge, does chrysler use mode 22 for their enhanced PIDs?
    Most common diagnostics are on $21 and $22, less commonly others. Decent approach if one of the obd2 addresses reports that data, otherwise more difficult.

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