How much time and travel miles, starting to shut-off - has happened since the light came on? I'm referring to the number of cycles you've driven the car since then. If it's been more that 15 times and the light is still on, it may be an indication of the system can not clear the code itself on it's own, it will need some help.
We've always said to just pull the battery cable + and just short it to ground for a few minutes to see if the system will restart with a new slate and forget the code so you don't have to worry. But this may also indicate a bigger problem with aging of the transmission and the ability of it's internal media - as a wear indication (being over-rev or high rpm and vacuum condition of deceleration) the system thinks it got stuck in that low-gear when it thought it can up-shift to a better gear.
You set the transmission in low-gear for the traction issue. It just may need to have itself driven and tested by you by putting it in the various modes of driving - like "Hill-assist" the button on the shifter itself as well as Traction Control being turned on all the time, try driving with it off (Warn Light on the Dash telling you it's off) even placing it back into Low for the purposes of driving on Ice - 2,000 RPM steady - for a few minutes to let it know it's a setting - not a glitch. Even pull the BRAKE handle and put it in PARK. Do this a few cycles so it can relearn the process it never had seen before so it can place data in the performance profiles of hi-RPM Rich to Lean conditions and valve advance so it can see that this was not an extreme condition caused by itself - you turn on and off settings to affect performance so it knows a driver is seeing road conditions and it's not caused by engine or transmission problems if everything else appears normal.
As we've said before - some codes will not clear due to the extreme conditions it was put under. So after those attempts listed above, try the battery reset again after these attempts - also try to find that DTC code in the HEC TEST mode - that code may be specific to the reason for the message and it can be something like a Chassis failure or a code it doesn't know anything about because FORD did not program the conditions' self-check/fail routines to clear on it's own. Why - for some conditions that cause the light to come on with that message to appear, need a hardware reset - and if the battery pull cannot do it - you may need to find someone with a setup that can clear codes without having to soak you for it.
To help with this - I've had Air-Bag codes set due to someone messing around with the kick panel under the drivers seat - either I get soaked for $1,000 bill in labor and parts to replace something they broke or contend with the error - I had to find a fix on my own and use a shorting stub on the DTC connector Reset-Data pin on the various Engine, ABS, and SRS connection points to clear codes that wouldn't otherwise clear.
If you notice there is no True RESET pin. This is a story for later. For in various systems - including the Fiestas' you have to short pins to ground to clear a code. As what a simpler DTC code scanner will attempt to do. But remember if you're not careful, you can FLASH a code into the system and require a Service call to a dealer to get this resolved. As had been seen on other Fleet vehicles others tried to fix on their own.
An example...
This is coming from Ford and Flexhub - as public domain being searchable.
