Flashing custom tune with custom tune already installed on car

Discussion in '2005+ Mustang GT 4.6L Tech' started by deezdrama, Jan 7, 2019.

  1. deezdrama

    deezdrama forum member

    Bought my 2010gt last jan. Got a CAI and steeda 93oct tune soon after I got the car and flashed with sct x4.

    I just installed longtube headers and catless H pipe and requested new tune file.

    When I get it do I need to reflash the car back to stock first, then upload the new tune to the handheld and then reflash with newest tune file?

    I vaguely remember reading to always revert back to stock tune and there was a debate about whether it was necessary or not but something about if you dont reflash to stock then the new tune just kind of updates existing custom tune which can cause problems and instead if reflashing back to stock it flashes as a clean slate or something to that affect.

    I just dont understand how it works. Like I know right now I have the stock tune on my handheld from when I flashed the 93oct steeda tune and it stored the stock tune.
    Now if I just upload the new tune to the handheld and flash it will it backup the first 93oct steeda tune on the handheld and thus replace the stock tune with it?
    Is the actual stock tune always going to be stored on the handheld regardless of how many times I flash a new tune without reverting to stock first?

    Someone hold my hand through this :D
  2. RocketcarX

    RocketcarX 95% of my weight is fuel

    The tunes are technically backed up on the PC you use to keep your SCT device up to date.
    If you add the new tune to the SCT it will become a custom tune option and you just load it, no need to return to stock
  3. 702GT

    702GT S197 Fanatic

    There's no need to go back to the stock tune when switching tunes on the same handheld. Just load the new tune and go. All of SCT's and Diablo (as far as I know) limit the number of times a handheld can be unmarried from a vehicle. Usually 4 or 5 times I think. After that you usually have to send it in to SCT or Diablo and have them refresh the unlocks (they charge for this service, plus shipping). The only time you want to return to stock is if you're switching devices, actually returning the handheld, or selling the car & keeping the handheld (buyer will need his/her own if the car is still modified).

    As far as KAM reset/relearn, it is not neccessary to return to stock for this. However, if you truely believe the tune has become corrupted, the first thing you should do is remove the aftermarket tunes from the device, do a firmware update if available, have the tunes updated if possible, and reload them to the handheld and reflash the car. The handheld will overwrite the existing tune for the new one. It always overwrites when changing tunes. If you still experience issues, contact the device manufacturer and they will tell you how to proceed, and likely need the device shipped in for diagnostics. In either case, I wouldn't burn up those return to stock uses up unless it's neccessary.
  4. Juice

    Juice forum member

    As it has been said, no need to return to stock OR erase KAM. A reflash clears KAM after the flash when it clears DTCs. After the flash, you will need to have the PCM relearn idle.

    As far as returning to stock, you lose an "Unlock" (new X4 has 5 unlocks) if you want to use tuner on another car OR if you had service done @Ford dealer and they update the PCM strategy.
  5. deezdrama

    deezdrama forum member

    Thanks guys. I flashed new file fri without returning to stock. Seems to run fine though i havnt drove it yet