Checking tyre pressure via the cluster

Discussion in 'Wheels, Tyres, Brakes & Suspension' started by Harrythedog, May 21, 2014.

  1. Harrythedog

    Harrythedog Hardcore MB Enthusiast

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    After following the manual I can't access the tyre pressures. After selecting the TYRE PRESSURE menu on the cluster all it asks is to reset RUN FLAT INDICATOR and doesn't show the pressures as the manual states. Am I missing something?
     
  2. miro

    miro Hardcore MB Enthusiast

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    It is optional. Not all cars have full monitoring.
     
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  3. OP
    OP
    Harrythedog

    Harrythedog Hardcore MB Enthusiast

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    Ah, so there's a warning system and a monitoring system?
     
  4. miro

    miro Hardcore MB Enthusiast

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    Yes indeed.
     
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  5. markjay

    markjay MB Club Veteran

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    The full Tyre Pressure Monitoring System (TPMS) is based on sensors with a battery and radio built into each tyre valve. This way the TPMS ECU can tell the pressure and temperature of each tyre.

    The basic TPMS has no such thing, instead it is based on the ABS/ESP ECU that uses the ABS wheel sensors to work out whether there is a discrepancy between the rotational speed of the tyres which may point to loss of pressure.

    The basic TPMS needs to be manually calibrated from the instrument cluster after all four tyres have been inflated to the correct pressures. But it does not know what the pressure is as such, so it can't tell if the tyre pressures are correct or not, just that they are all (roughly) the same.

    The basic TPMS was introduced in order to meet the mandatory requirement for TPMS with run-flat tyres ie so that the driver is alerted in case of a puncture. It can be enabled or disabled using STAR, and at the time cars without run-flat tyres came with TPMS disabled - and the dealers would charge around £50 to enable this feature if your car was not equipped with run-flats.

    I believe that in recent years all cars had this option enabled by default, run-flats or not, though I am not sure.
     
    Last edited: May 21, 2014
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