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Alert #104 (TCM: Lost DMC comms)

Discussion in 'Roadster: Technical' started by gregd, Jul 8, 2018.

  1. gregd

    gregd Active Member

    Dec 31, 2014
    Hi folks,

    I've been getting widely-spaced, and seemingly random Alert #104 (TCM: Lost DMC comms). Car is usually just sitting there, sometimes just when charging starts (e.g. the daily top off). Nothing bad seems to happen, and according to the logs, they go back to the dawn of time (first one 3/2010). The general trend is slightly upwards, with a few dozen of them per year now. Now that I have an OVMS module in the car, I'm more aware of them.

    Any ideas on a cause, or if they are a cause for concern?
  2. petergrub

    petergrub Member

    Jul 6, 2016
    Phoenix, Arizona
    Start with the CAN communications and power delivery to the TCM—Traction Control Module. Check the RHC12 PEM Logic connector under the PEM for recessed or pitted pins. It's the big black and red connector; let me know if you need instructions on how to access it safely.

    Then, check the RHC19 TCM connector under the left side of the trunk that connects to the TCM module, and again look for recessed or pitted pins. You can apply a contact cleaner to remove the build up oxides/corrosion and lubricate the connections.

    Lastly, check the fuse in the fuse box outside of the trunk on the right side. It sits between the trunk and the PEM and can even be an inline fuse in some cases.
    • Helpful x 2
    • Informative x 1

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