Out OF Sync CAN

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  • greasybob
    Senior Member
    • May 2008
    • 1590

    Out OF Sync CAN

    Had an 08 Silverado 1500 with ABS and Service 4wd messages. I found I had no scanner communication with either the TCCM or ABS module. I checked Power and gounds at the TCCM, all good. Next I checked the CAN signal into and out of the TCCM with the scope. The pattern looked good, like a normal CAN pattern. Hmmmmm? Since I was scoping the CAN at the TCCM any ways I thought I would scope the CAN at the DLC at the same time on another channel to compare signals. There it was, the problem, the 2 patterns did not line up. I think that the ABS and TCCM were making there own signals but not getting through to the main line at the BCM. The only module between the TCCM and the BCM is the Onstar Module. Replaced the Onstart Module and all is in sync now and the TCCM and BCM communicate with the Verus again. Must have been an open in the ONstar.
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  • Witsend
    Banned
    • Nov 2012
    • 2942

    #2
    Replaced the Onstart Module and all is in sync now and the TCCM and BCM communicate with the Verus again. Must have been an open in the ONstar.
    Nice work Bob , but does someone still want or need On Star on a 10 year old vehicle? What happens if you just left the On Star module disconnected, or if no go wired in series, jumped the 2 in pins to the 2 out pins to complete the bus circuit to the DLC ?

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    • phill57
      Senior Member
      • Oct 2007
      • 474

      #3
      Great Find

      Originally posted by greasybob
      Had an 08 Silverado 1500 with ABS and Service 4wd messages. I found I had no scanner communication with either the TCCM or ABS module. I checked Power and gounds at the TCCM, all good. Next I checked the CAN signal into and out of the TCCM with the scope. The pattern looked good, like a normal CAN pattern. Hmmmmm? Since I was scoping the CAN at the TCCM any ways I thought I would scope the CAN at the DLC at the same time on another channel to compare signals. There it was, the problem, the 2 patterns did not line up. I think that the ABS and TCCM were making there own signals but not getting through to the main line at the BCM. The only module between the TCCM and the BCM is the Onstar Module. Replaced the Onstart Module and all is in sync now and the TCCM and BCM communicate with the Verus again. Must have been an open in the ONstar.
      That's one for the record for sure. I'm not sure I would have caught that right away. Good job!

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