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Thread: Where do engine RPM messages come from?

  1. #1
    Potential Tuner
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    Sep 2014
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    Where do engine RPM messages come from?

    Hello,

    This is my first post here.

    Vehicle: 2006 Chevrolet Equinox

    I have a couple of questions I hope someone can answer:

    1) What module broadcasts the engine RPM messages: ECM, PCM, or BCM? Any idea How often this message is sent?
    2) Same question for the Vehicle speed messages: ECM, PCM, or BCM? Any idea How often this message is sent?

    Thanks

  2. #2
    Tuning Addict 5FDP's Avatar
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    ECM=PCM depending on what country you live in.

    RPM comes from the PCM, but I couldnt tell you how often and not even sure how you'd figure that out.

    For vehicle speed thats still like a PCM or TCM (trans) thing, they will tell you the speed the car is going.

    BCM is all body control fuctions like radio, windows, hvac etc etc.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
    Senior Tuner 10_SS's Avatar
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    ECU/ECM = Engine Control Unit/Module (for cars that have a separate CU for Engine, and one for Trans).
    PCM = POwertrain Control Module (For cars that have a single CU for Engine and trans).

    GM for example calls it an ECU for cars that have a Auto Trans and the trans has it's own controller, so there is only one controller for the Engine.. and it's called Engine Control Module.. Older cars that have no trans controller.. the Engine Controller controls both the Engine and the trans, these are called Powertrain Control Modules.. (PCM).

    Depending what method your gathering data... most standard ELM based loggers can read PID's at the date of 0.100 to 0.300 times per second...
    2010 Camaro LS3 (E38 ECU - Spark only). MS3X running complete RTT fuel control (wideband).
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