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Description and Debugging of the L9135PD Injector Driver IC

By on March 18, 2017
automotive l9135pd injector driver ic










I got a problematic ECU ( Electronic Control Module ) in my service now days, the request from the customer company was does the ECU is faulty, actually the ECU don’t command the injector no. 3 on the vehicle. I decide to take the job and check what could be wrong. After 30 min I came out with a shorted IC pin no. 4 which is actually the commanding pin for the injector. I tried to find a schematic for the IC on the Net, but with no luck. I had no other option than to debug the circuit and try to figure out how the IC is working.

This is a very basic circuit and also a basic description, but I think if I found something like this at the moment on the Net. when I searched for, I would be very happy!

So, here is the work from me and I will share this with other technicians who face problem with this IC or similarly one. This is a solenoid driver IC, I assume this is in lot of automotive applications and maybe in other too. The major think is there are four input pins and four output pins which are base on some sort of FET or some power transistors.

But there are some sort of communication pin too, which tells the power IC ( right down on the ECU picture ) if there is some short circuit to shut down the power to the IC and/or reset the IC.

The L9135PD is powered from 5V voltage, but I assume it could be powered from 9 maybe 12 or a bit higher voltage too.

automotive injector driver ic

l9135pd ic

This article was prepared for you by Christian Robert Adzic from Novi Knezevac-Serbia.

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  1. Albert van Bemmelen

    March 18, 2017 at 3:35 pm

    Thanks for this very special article, and another one, on automotive electronics Christian. If I understand it well you replaced the L9135PD Injector Driver IC because the old one short circuited?

    • Chris

      March 18, 2017 at 4:46 pm

      Hi Albert!
      Yes, I replaced the old bad ic with another one used but a working one.
      Now is the ECU fine.

      Thanks for supporting my articles.
      My best regards.

  2. Ander Gopee

    March 18, 2017 at 11:11 pm

    Hi Christian, Thanks for the informative article. I too get these CPU's to repair.... Sometimes they can be very difficult to repair and other times they are quite simple. Tell me something... How do you test these boards? Do you have a test jig you made or do you test them on the car? I would really like to get something to hook them up to for testing. Most of the time I would only do component check and that can be quite tedious. Thanks for the article.

  3. John K Kasonde

    March 19, 2017 at 8:08 pm

    Hi Christian,
    A very good tip for electronics Technicians.It will be nice to have some tips on Hi Fi Stereos especially Samsung with a moving control panel.

    Stay blessed,

  4. Mahmoud

    March 19, 2017 at 8:14 pm

    Hi Robert thanks for good repair I think you are brave because repair EcU very deficault.

  5. Chris

    March 19, 2017 at 8:58 pm

    Hi Mr. Gopee!
    Most of time I like if the car is beside me, but not all the situation can offer me this comfort to have the car also.
    Some time I can hook up my diagnostic tool which is the Delpi DS150 VCD+ and power on the ECU through lab power source.
    If I have luck and the ECU will not ask for the immo of the car then I can read the DTC from the ECU and the most important think is I can make so called "Click Test", which means I can activate the let's say injectors one by one through the diagnostic tool and read the output on my oscilloscope or I can connect an injector or relay and check the output.
    But, also, not in all situation is this possible.
    The diagnostic tool I connect in this order:
    1. Connect the CAN and or if needed the K-line from the OBD2 socket of the diag tool to the CAN and/or K-line pin on the ECU
    2. Power on the ECU through the lab - bench power source
    3. Power on the diag. tool through the OBD2 socket where the pin 16 is +12V pin's 4 and 5 are GND.
    4.I have to give +12V to the ignition pin on the ECU.
    5. In the diag tool you have to select the right car model and year etc..
    You powered on the ECU, connected the diag tool and can start to play.
    I hope this will help you and other's too.
    My best regards.

  6. Robert Calk

    March 20, 2017 at 2:17 am

    Thanks Chris. Good job.

  7. Humberto

    March 20, 2017 at 9:11 pm

    Thanks Chris for sharing this article with this community.

  8. Parasuraman S

    March 22, 2017 at 1:07 am

    Good Job!

  9. Charlie Duncan

    April 4, 2017 at 1:31 pm

    It wasn't exactly clear as to what your solve was for the problem of injector #3 not firing but as I read the comments I find you replaced the IC chip from old stock.
    Definitely a good find as I'm sure it took a lot of patience and steady hands.
    Did you try to buy a new IC?
    I would think that some of these chips would be proprietary and not easy to come by and even if you did locate one the cost would make the repair too expensive.
    As I said it was definitely a good find.
    Could you disclose what make automobile it came from so we could keep this fix in mind if we encounter a like problem.

    • Chris

      January 3, 2018 at 6:10 am

      Yes, I got the IC form a scrap ecu.
      Not possible to buy it easy in my area.

      I don't know what type of vehicle have this ic in their ecu, but all IAW 5NF T1
      ecu I suspect they have the same ic.

      So, check on the net for compatibility of this ecu vith cars and you will get the list of affected cars.

      But, I assume this problem is not a major problem on this type of ecu.
      I mean, it is not a manufacturer problem.
      It is maybe a cos of a wrong testing method of the injector done by a service person.

      My best regards.

  10. parashu ram singh

    May 1, 2017 at 6:00 pm

    how to deduct IC faulty in all cases with using tester/multimeter/any other equipment is it possible or not tell me as to why i know a man who is working in this field approx 20 years...

  11. traian

    May 10, 2017 at 2:49 am

    Hi,my Reanult Twingo 1,2cmc,16vyear 2001 shows 108 degrees water temperature but the engine is cold,the resistance at sensor wires is 150 ohms,sensor not conected,something is wrong in ECU,what,i dont know,you know?

    • Chris

      January 3, 2018 at 6:05 am

      Sorry because I recognized late this question.
      If you don't solved your problem, pleas do a diagnostic test and check for DTC's on your vehicle ecu and share with me.
      Maybe I can help you.

      My best regards.

  12. Mahdi

    December 12, 2017 at 11:21 pm

    Hello, after replacing this one, i must to upgrade Ecu or not. Because the injector 3 always fails my Fiat stilo.

    • Chris

      January 3, 2018 at 6:03 am

      If your problem is the same as in this ecu what I repaired, than you don't hawe to do any software upgrade.
      It will be fine.
      This IC is just a simple solenoid driver ic...

      My best regards.

  13. NAIL

    August 16, 2019 at 5:13 pm



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