Over the last 3 month my focus has had a engine system fault message flag up on the dash with a red indicator. Iv tried everything to found out what the fault is but can be intermittent and go . The car runs fine with no loss of power . Would this message mean it needs a pat fluid refill additive? .. I'm a little lost as normal code readers don't pick anything up . Like I say car runs and starts fine .

Hi, I had the same thing on my fiesta, turned out to be a glow plug. Does anything flashes in the dashboard? I had a cog with an exclamation mark. What app did you use to read faults? I tried a free version first but only after upgrading to pro it was able to read the fault code ( not sire if i am allowed to say which app)

Hi thanks for the reply . It was 2 garages that have plugged it in with no codes that came up . And even sent it to a guy over the last week to see if it was an electrical problem . but again he checked everything and couldn't find anything . But now the fault is just constant.. But drives fine no smoke .

Hi! Then not sure what that would be - i have something in the dashboard so at least I knew there was something wrong ( i also have the red led that you have)

Could be dirty egr dirty sensor split hose dirty fuel filter dirty air filter , the message can meen a host of things , start cheep work towards expensive . 

Fault sorted . It was a pat fluid refill ! But as I found this out and planned to do the pat fluid refill the engine management light came on . Cost me £40 for the filling kit off Amazon .  But after you will need to get someone to reset the warning ⚠️ lights . then all done . Works a treat hope this helps anyone here .