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Thread: VIN Change

  1. #1
    New Member
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    May 2018
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    Default VIN Change

    Hi first post here, I could use a little help.

    I'm having trouble rewriting the VIN on a 99 F-Body LS1B ECM os 09360361. I'm currently able to write the new non GM VIN to the ECU using the bidirectional controls in Scan V7.5, and the updated VIN will remain stored after cycling the ignition. The problem is after I either remove constant battery power or read the calibration from the ECM it will revert back to its original F-Body VIN. If I leave constant power on and cycle the ignition I can reconnect to it and it will display the new VIN on the handheld or pass-thru. I cant seem to get the updated VIN to commit to hard memory. I even let the ECM sit with constant power/ignition off for awhile and still had the same results.

    Some notes about my setup. ECM is powered on the bench through a harness and I'm using a V2 with the latest updates. I verified pins 20 and 57 on the blue connector have constant power and pin 19 has switched power. Pins 1 and 40 also have ground. My only concern is that I have it powered by a "dumb" battery charger that is most likely putting out some nasty DC. I can maintain a pretty steady 12.8v but I dont know how clean the power is. Has anybody run into an issue like this before? Thanks in advance!

  2. #2
    EFILive Developer Site Admin Blacky's Avatar
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    Mar 2003
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    9,465

    Default

    Do you have the option to monitor the current draw of the PCM while it is on the bench? If so, watch the PCM's current draw after you switch off the ignition while power is still maintained to the PCM. You should see the current draw drop significantly as the PCM enters sleep mode (takes about 10-20 seconds*). After ignition off and prior to sleep mode the PCM performs its housekeeping tasks which includes saving the VIN to flash memory, so once it has entered sleep mode (i.e. the current draw drops) the VIN should have been saved permanently to flash memory.

    * Coincidentally, the timer countdown you see in the EFILive software after reading/flashing a controller is a simple way to allow the controller to finish its housekeeping tasks and enter sleep mode. The countdown in the software is just a fixed timer - it does not actually monitor the controller to determine if/when it enters sleep mode - to do that would simply keep the controller awake.

    Regards
    Paul
    Before asking for help, please read this.

  3. #3
    New Member
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    May 2018
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    Default

    Thanks for your reply Paul! I actually tried a different power supply and it worked perfectly on the first try. So something in that other supply is keeping the PCM from sleeping.

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