MIL Light In Ford

[d2dave]

My SWMBO car is having a regular visit from the Mil light.

When I put my diagnostic tool on it is saying that it is too rich on the right bank.

I clear the fault, which can come back any time between a day or two to the next drive.

My question. Is the oxygen sensor likely to be faulty or could there be an other problem causing this too rich scenario, which the oxygen sensor then reads and reports to the ECU?

Car is an 06 Ford LTD with 5.4 litre V8 running on liquid injection gas.

[bee utey]

Failed oxygen sensors tend to read too lean more often than too rich. I'd be running it on petrol for a few days to see if it still throws the MIL. There could be a dribbling petrol injector that's causing the rich fault.