Discussion in 'General Electronics Chat' started by Tree1, Nov 2, 2011.

  1. Tree1

    Thread Starter Member

    Nov 30, 2010
    Does anyone know if the ECU in automobiles monitors the base current of transistors and sets code if it is more or less than some pre-set value stored in the ECU. Just curious.

    Also, if one transistor is driven by another such one transistor(Q2) is driven by the collector output voltage of the other(Q1). Q2 switches on when Q1 is off. Let's say that the base resistor was badly chosen( too low for instance). Can that have devasting effects on Q1. If Q2 burns, what will mostly happen to Q1 ?What is the worst case scenario?

    Thank you in advance.
  2. bertus


    Apr 5, 2008
    Last edited: Nov 2, 2011
  3. SgtWookie


    Jul 17, 2007
    Well, not necessarily "the base current of transistors" - but it does monitor voltage & current levels of various circuits.

    If a base current limiting resistor value was so low that the maximum base current were exceeded, the transistor junction could be destroyed. If it was a large overcurrent, the case of the transistor could be fractured into pieces when the junction was vaporized.

    But, that's not terribly likely to happen in an ECU unless there were a significant fault external to the unit. Manufacturers have to honor the vehicle warranty for whatever the period was; replacement of a large number of faulty ECU's would be a huge financial loss. So, the manufacturer has such components carefully engineered to last until well after that occurs.

    Most vehicles manufactured nowadays will still be serviceable at 100,000 miles with nothing more than routine scheduled maintenance.
  4. debe

    AAC Fanatic!

    Sep 21, 2010
    Not quite sure what your after Tree1, But Most ECUs are pretty well protected & sensor inputs are small signal either a var resistance pulling a 5V dc down or feeding small signal pulses into the ECU, rarely above 5V. This is some of a course i did when working for a Ford dealer some years ago, when you was taught what goes on in & around the ECU. These days its more replace a part & hope it fixes it & nevermind how it works. Im one of those who is curious as how it works & why it failed.
  5. Tree1

    Thread Starter Member

    Nov 30, 2010
    Thank you guys for help and re-opening my thread. I am only trying to understand electronics circuits but specifically as it relates the automotive industry because this is my field of study. Someday, it will become career for me, so I am just trying to understand as much as I can. Also, thank you for the attachments.