cog light ON but no codes appear when tester connected, also the engine management light is NOT on . But comes on when I turn on the ignition and goes off as normal when the engine starts and the glow plug light works as normal to .The car is in Limp mode so it’s underpowered but everything works . The car goes like a rocket when it’s going properly . I disconnected battery and it went off for a while and it ran great until it came back on .  I have changed  , glow plugs , oil & filter , air filter , fuel filter , cam shaft sensor , glow plug relay in fuse box  which is cube shape about  25 mm in size . I cleaned a sensor in the  air intake pipe  And I changed the thermostat to  I also purchased a Preheat relay as well which has a bracket shaped end  and a hole in it to bolt it on ,and that one is about  75 mm long BUT I cannot find the Location of it any where on the car !  Otherwise I would change that  as well.   I also noticed this too on a hot day recently I drove about 20 miles with the cog light on in limp mode and parked up in a very sunny spot and when I returned about 1/2 hour later I started the car and the Cog light went off and the car drove Great for about 15 miles then the light came back on for the rest of the way home in limp mode and been on since. Disconnecting the battery for a while does not turn it off  !!!  Any ideas Guys or Gals 

feel free to email me.  [email protected].  United kingdom

9 hours ago, Rob Smurthwaite said:

light ON but no codes appear when tester connected

Generic code readers won't read Ford specific DTC's 

Use FORScan