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Using MX sensors for standalone system

16 Views 0 Replies Create Time: 2026-04-04 18:26:38


  •   Level 1   
    (5) points
    David Lynch
    2026-04-04 18:26:38
    Hi  

    I’m reverse-engineering a set of 433.92 MHz TPMS sensors and need help confirming the packet format / protocol.

    Known sensor IDs:
    LF: 0CAD7FB4
    RF: 0CAD7949
    RR: 0CAD87D6
    LR: 0CAD812E

    What I already know:
    - LF decodes cleanly and matches my handheld very closely: 208 kPa / 22 C on my RF decode vs 206 kPa / 22 C on the handheld.
    - Packet appears to be 9 bytes:
      ID[4] + flags[1] + pressure[1] + temp[1] + counter[1] + checksum[1]
    - The checksum seems to be XOR of bytes 0–7.
    - Pressure scaling appears close to 1.379 kPa per raw count.
    - Temperature appears close to raw - 50 C.
    - Some sensors decode cleanly, others mostly come through as corrupted/checksum-fail packets.

    Can anyone confirm:
    1. The exact sensor family / protocol these IDs belong to?
    2. Whether the packet structure above is correct?
    3. Whether pressure and temperature scaling above are correct?
    4. Whether these sensors use different bit timings / data rates between wheels or sensor variants?
    5. Whether Autel-triggered wake-up should produce an immediate RF reply, or if motion/pressure change is also needed?
    6. Does the sensor transmit battery level?

    Tags: mx , sensors

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