Ford Fiesta air bag light

If it flashes four times, there usually is a yellow connector under the front seat. Just unmaking and remaking it sometimes cures the problem.

just to add to whitinhames solution,for your own safety disconnect the battery for 15 minutes before working on the airbag system,

Check this ,

" If the air bag light flashes four times indicating a fault with the pretensioners, with the ignition off, disconnect the pretensioners yellow connectors which are usually positioned under or very near the seats. Wait a couple of minutes and then re-connect them. What happens is sometimes the circuit get a spike and illuminates the light, disconnecting then resets the system and the light goes out. If the light continues to flash there is probably a fault with one or both of the sensors.