My guess would be you had used the car. Stopped for a short time like getting fuel & started up. The lambda sensor on my 3 l Roadster did this on the passenger side.
I bought the app "Torque" (though the free one will clear faults) & an OBDII dongle on e bay.
I did buy a cheap hard wire OBDII reader but it didn't work on Fords.
Lets us know what the code is please.
I solved my issue by not using cheap supermarket fuel.It seems they can glaze the lambda sensor.
They are also prone to lean engine warnings. Check for air leaks after the MAF sensor including the crank case ventilation hoses.
