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Thread: ECM will not write

  1. #1
    Tuner in Training gearheadib's Avatar
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    ECM will not write

    I have 2004 hummer. I converted it from a clutch fan to electric fans So i add the pins in the ecm. then put a 12 charger on the battery plugged in the laptop, read the ecm, changed the fan settings and go to write calibration back and i get a write time out error? what can i do now because it wont start. I think i attached the file if not i will try again.
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  2. #2
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    Not sure if this helps but I've had aftermarket accessories like radios that tied into the network cause me problems while re-flashing.

  3. #3
    Tuner in Training gearheadib's Avatar
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    Quote Originally Posted by Xeen1901 View Post
    Not sure if this helps but I've had aftermarket accessories like radios that tied into the network cause me problems while re-flashing.
    It has a aftermarket radio but it was off.

  4. #4
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    Try pulling the radio and radio amp fuse. If it still won't write then it is likely the chime adapter you used. Some seem to be better than others. About 1/2 the ones I encounter won't let you read/write and the other 1/2 will. You will have to either flash it with a bench harness or pull the radio and disconnect the chime adapter from the harness. This applies to 03-07 classic trucks with RAP. If it has an aftermarket alarm or remote start that ties into the purple data wire on the ALDL plug that will have to be disconnected.

  5. #5
    Tuner in Training gearheadib's Avatar
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    Quote Originally Posted by 2xLS1 View Post
    Try pulling the radio and radio amp fuse. If it still won't write then it is likely the chime adapter you used. Some seem to be better than others. About 1/2 the ones I encounter won't let you read/write and the other 1/2 will. You will have to either flash it with a bench harness or pull the radio and disconnect the chime adapter from the harness. This applies to 03-07 classic trucks with RAP. If it has an aftermarket alarm or remote start that ties into the purple data wire on the ALDL plug that will have to be disconnected.
    okay that makes sense it would chime when it failad i will remove it and see.

  6. #6
    Tuner in Training gearheadib's Avatar
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    Quote Originally Posted by gearheadib View Post
    okay that makes sense it would chime when it failad i will remove it and see.
    well chime is now unhooked and i get a controller timed out error now

  7. #7
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    I usually have to unplug everything, not just the chime.

  8. #8
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    Have you looked at the purple ALDL wire?

  9. #9
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    Just noticed the "now it won't start" in your first post. See if the scanner will connect. If it won't you may have bricked the PCM.

  10. #10
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    If you have a stereo to steering wheel interface controller installed to keep the steering wheel stereo controls, chances are.. this is your issue......Pull radio fuse and try writing in low speed... un-check the *Use High Speed* in the write window. If that doesn't work, you most likely bricked the ECM... Gen III's can be real touchy... ANY voltage drop/draw can cause a brick...
    Sometimes I stick an ice cream cone to my forehead and pretend I'm a Unicorn...!