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Thread: Have to read before write

  1. #1
    Tuner in Training
    Join Date
    Feb 2018
    Posts
    22

    Have to read before write

    I have a LS swapped 67 Camaro with a 411 ECU. Over the winter I did a lot of rewiring, and updates to the fuel system. Yesterday I went to tune from E85 to E100. Just 1 value change. I couldn't write to the ECU. It would display the communication message, the downloading boot loader and when it says writing 0.0% the fuel pump kicks on like the ECU is being reset. After about 15 seconds a failed message shows up. This happens over and over.

    I did figure out that if I read entire the ECU I can the write to the car just fine but if I turn off the engine I have to read entire again to be able to write to it.

    Please help me figure this out. Everything worked fine for 2 years now. I have downloaded 4.6 and the beta 4.7 and still same thing. I even tried a spare 0411 and it does the same thing.

    Thanks in advance,
    Greg

  2. #2
    Tuner in Training
    Join Date
    Feb 2018
    Posts
    22
    Update 5/2

    Well today it wont write any more. I went to the race track and made one pass. I was lean so I tried to change some tables but nothing I tried would let me write.

  3. #3
    Tuner
    Join Date
    Dec 2008
    Location
    Houston, Texas
    Posts
    129
    Voltage issue? Ive had that happen before when I had a weak battery on customers vehicles.

  4. #4
    Tuner in Training
    Join Date
    Feb 2018
    Posts
    22
    I have a fully charged 16v battery but thanks for the reply

  5. #5
    Tuner in Training
    Join Date
    Feb 2018
    Posts
    22
    Ok, so I installed the 12v battery and can read and write just fine. I tried running the MPVI off 12 and the ECU off 16 and that didn't work. So what I figured out is the ECU does not like 16.7 volts. I have tried 2 different 0411 and both exhibit the same issue when powered from 16.7volts. what I did to fix this issue is to run the ecu off a alarm sized 12v battery and the rest of the car off the 16v battery. Works fine.