Correct, yes check the connections to it, to test it you really need a ocilliscope, some try using an AC voltmeter but you need to test when car is moving. Pretty sure it will be this.
The best way would be to use the self diagnosics on the car, hold in the trip counter and turn ignition to on position and hold a "Gauge Sweep" will be performed (Will reset trip meter but no biggie, will NOT reset total millage) and all dials will go to max and then back to 0 if you keep pressing the trip counter you will get to one on the display think it's number 6 where "DTC" will be displayed on the LCD (Diagnostic Trouble Code) it should display a code here if you can post the code back that will defently tell you the problem. Im 99.9% sure this will work on your car as not knowing Fiesta that well but it certainly works on Focus/Mondeo.
Martin