[DirtyD]

If you are like me and many others here that use the SCT X3/SF3 handheld tuner for uploading a tune to your car, then you have probably have a failed upload one or twice, or even more than that.

FIRST AND FOREMOST, save your stock tune file from your X3/SF3 on to your computer, flash drive, or other media type so you can always have it in case your handheld loses it or you update the firmware without returning to stock.

I am posting this thread in hopes it will become a sticky for anyone in the future that does not know how to resolve this issue, so they don't have to take the time for someone to respond to their post about it while stranded somewhere.

The information and suggestions shown here ONLY correlate to 2011-2014 Mustangs.

Cause:

The Ford Copperhead ECU requires a certain voltage to be maintained at all times during the flashing process. Sometimes even a small variance can cause the ECU to go into failsafe mode and close all access to the ECU if there is not enough supporting voltage. Between the handheld communicating with the ECU, and the ECU trying to handle other duties while tuning, this can turn into a rather frustrating and common occurance. Open doors, radios, other accessories may cause this issue as well, or add to it.

Effect:

When the voltage drops below what the ECU needs, all access ports and communication from the ECU stops. So your handheld that was currently uploading your custom tune or stock tune now has given you the message "Download Failed".

Solution:

The one option that I've found to work best for fixing the failed upload to allow you to return the car to stock si listed below, as a procedure.

1. Return to the home screen of the X3/SF3 handheld and disconnect the handheld from the OBDII port.
2. Turn on your headlights to the "ON" function, NOT Auto!
3. Using an 8mm socket and ratchet wrench, disconnect the NEGATIVE (-) battery lead from the terminal. Make sure your car is unlocked and the windows are down before doing this! Also fee free to just leave a door open.
4. Wait at least 20 minutes for all electrical charge to be drained from the car. This would be a good time to grab a beer, play a game on your phone, or take a nap.
5. Once you have waited for the system to drain, turn your headlight switch to "OFF".
6. Reconnect the negative (-) battery lead to the battery.
7. With all doors closed, headlights and other accessories turned off, proceed to return the car to the stock tune.
8. If you successfully return the car to stock, follow Step 7 and attempt to reupload the custom tune.
9. If Step 8 is successful, go drive the car.
10. If the car fails to upload again, retry Steps 1-8 again, or call a tow truck. That is your decision.

Future Suggestion:

There are a few different routes and suggestions you can use to prevent this from happening in the future.

1. Use a trickle charger or some type of battery charger to help the electrical system maintain a steady voltage while tuning. This MAY allow you to keep doors open, use the radio, or other accessories without problem, but I have not confirmed this to be true.
2. Turn off ALL lights, keep all doors and trunks closed, ensure your radio is turned off and that your air system is completely off, not just the A/C turned off. If you have to roll down your windows, do so before attempting to upload your tune.

Personally, I would recommend that you tune the car at home or somewhere where you won't be SOL/toolless and/or waiting for the car to cool down with the hood open, placing a shop fan or something of the sorts on the engine bay as an option.

Hopefully this will help anyone else in future need of this answer to a recurring problem.