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Thread: current rating of FC pin on 2RZ-FE ECU?

  1. #1
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    Default current rating of FC pin on 2RZ-FE ECU?

    First of all, thanks for the great community! The depth of knowledge is excellent and everyone is friendly and helpful. Appreciate being a part of it. :-)

    So, I’m an American and own a 1996 Toyota Tacoma pickup with the 2RZ-FE engine. Partially inspired by information found on this site, I recently replaced a bad circuit opening relay with a standard 30A Bosch-style cube relay.

    I connected the coil ground of my new relay (85) to the FC pin of my ECU, coil positive (86) and relay input (30) to the output of the EFI relay, and connected 87 to the fuel pump. I also added a snubber diode across 85 / 86 to protect the FC pin of the ECU.

    Everything works great, and I am really happy, but I’m concerned that the standard cube relay may be overdriving the FC output on my ECU. A standard cube relay draws 150mA, compared to about 100mA from my original COR, that's a 50% increase.

    Anyway, my ECU PN is 89661-04160.
    Short of having to remove the ECU to look at the output transistor, does anyone know the current rating of the FC pin or can make an educated guess?
    Can this ECU handle 150mA steady state v. the stock 100mA?

    Thanks!
    Berliner

  2. #2
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    Default Re: current rating of FC pin on 2RZ-FE ECU?

    Hello all,

    I was able to remove the ECM this weekend and open it up.

    In the Toyota service manual, the FC input is "E5-14" which is pin 14 in the 3rd connector. I traced the FC circuit on the board from pin 14 to the FC transistor.

    Please find below links to three pictures. The third shows the transistor. It is marked "GA" or "CA" and "5Z". The picture is not so clear, but I verified the marking with a jewelers loupe.

    Does anyone know what this component is or even have a data sheet? I just want to know what the current rating is.

    Thanks and have a great Sunday!
    Berliner JFK

    https://ibb.co/d7f0P3s
    https://ibb.co/TtYYC3Z
    https://ibb.co/qMFmxwT
    Last edited by Berliner; 24-03-2019 at 09:54 AM.

  3. #3
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    Default Re: current rating of FC pin on 2RZ-FE ECU?

    I think I may have found it: http://www.s-manuals.com/pdf/datashe...8_infineon.pdf

    If this is in fact the component ("CA" code) then it looks like I might be OK. If I am reading things correctly, DC collector current is rated at 1A, which is well over the 150mA I need.

    Do you see it the way I do?

    Thanks!
    Berliner JFK

  4. #4
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    Default Re: current rating of FC pin on 2RZ-FE ECU?

    OK, finishing off this post, in summary:

    I wanted to know whether I could use a "cheap" relay (= 80 ohm coil) with the FC pin input of my 1996 Toyota Tacoma.

    The original COR has an internal resistance of 125 ohms, so pulls 100mA steady state, the cheap relays pull 150mA. Would that overload my ECU FC pin?

    I opened my ECU and found out that my FC pin was connected to a bcx68 NPN transistor, datasheet here: http://www.s-manuals.com/pdf/datashe...8_infineon.pdf

    I also saw that there was a current limiting resistor in between the FC pin and the emitter of the above transistor, measured value was 3.9 ohms. Here is a pic: https://ibb.co/TtYYC3Z

    A current limiting resistor of 3.9 ohms would limit max current to about 3A (assuming 12V). Also the datasheet of the transistor, if I read it right, implies that the steady state sinking current of that transistor is 1A, peak 2A.

    Given all these clues and putting it all together, I think I can say the following:

    The ECM FC pin of my 1996 Toyota Tacoma 2RZ-FE (PN 89661-04150) can absolutely handle the 150mA required by a standard cube relay (80 ohm coil) as opposed to the 100mA for my standard COR.

    This is good news for me, who, would like to use a standard cube relay.

    Thanks for the inspiration to go through this mental exercise and work, especially thanks to @wilbo666 who brought me to this website and gave me the courage to dig into this and answer the questions! :-)

    Berliner JFK

  5. #5
    Junior Member Grease Monkey
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    Default Re: current rating of FC pin on 2RZ-FE ECU?

    Good to hear you sorted it out haha. Almost everyone, including myself on a 1uz and 4age, just use a standard relay for the fuel pump relay and i haven't heard of anyone blowing up there ecu. i think you will find that even different brands of relay will have different coil currents as wel

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