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TPMS fault 409 - temperature dependent?

Discussion in 'Roadster' started by sethr, Nov 29, 2013.

  1. sethr

    sethr CPO Roadster #1089

    Joined:
    Mar 24, 2013
    Messages:
    152
    Location:
    Fairfax, VA
    Hi all, I am wondering if anyone else has noted seeing fault #409 (Tire Pressure Monitor Service Required) show up when it is near freezing? I went on a visit to a friend yesterday when it was around the freezing mark outside, (30 minute drive) and when I was nearly there the fault popped up. When I arrived, I parked, pulled the handbrake and went to the tire pressure screen - no readings as expected. I was parked out in the sun and thus the Roadster got warmed up, relatively speaking. When I left, after dismissing the fault message (twice, by accident), the dash warning symbol went away (as well as the VDS message), and stayed away until I was nearly home, when the fault message/tone/dash warning light reappeared (still around the freezing mark outside). I parked in my garage (which is about 15 degrees warmer than outside), and today, when it was in the mid 40's I went for a drive, first dismissing the fault message (left over from the day before I assume?) twice, and it stayed clear. After a few minutes I pulled over, still no readings, but then I figured maybe that wasn't long enough for it to read the TPMS, so I pulled over and tried again, and there were the tire pressures. I remembered reading here that it can take 20 minutes for the fault to re-appear after dismissal, so I kept driving to the 30 minute mark. No fault, and back home I checked once again, the tire pressures were there. I should have mentioned: I tend to drive without cabin heat, my little oddity... That means both the outside and inside of my Roadster went from 45 to about 32 degrees before the fault popped up each time yesterday. I don't know where the TPMS receiver is, but on my test today I dressed lightly so I could stand keeping the cabin heat on. Sorry to be so verbose, but I want to be as specific as possible so you all can tell if you have had a similar experience. I'm thinking it might be a connection that is not quite as tight as it might be.... Anyone have any thoughts or experience to share? Thanks!
     
  2. Doug_G

    Doug_G Lead Moderator

    Joined:
    Apr 2, 2010
    Messages:
    15,848
    Location:
    Ottawa, Canada
    It's certainly possible for electronics to be temperature sensitive. In fact you have to design for temperature range.

    It could be something as simple as a flaky connector - unplugging and reseating might fix it. Or it could be a semiconductor device that's out-of-spec and you'll have to replace the whole module.
     
  3. markwj

    markwj Moderator, Asia Pacific

    Joined:
    Apr 10, 2011
    Messages:
    3,655
    Location:
    Hong Kong
    If you have OVMS, or can pull the logs and use a log viewer, you can get a lot more visibility on this.

    In my experience, it is most likely either a single sensor or antenna at fault (two antennas - one front, one back). If there is any fault, the car tpms screen shows nothing, but OVMS/logs will show you the sensors still working.

    One other aside: the fault shows after 20 minutes because the system is designed that if the car is on, but gets no tpms signals after 20 minutes, it will alert. You can repeat this by turning on the car, and leaving it stationary for 20 minutes - you'll get a tpms fault even if tpms is working just fine. You gotta spin the wheels to get a reading from the sensor.

    As for cold, it is definitely possible that could aggravate a marginal reception of signal.
     

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