Whilst troubleshooting some suspension issues earlier this week I noticed some other ECU codes logged but lost the diags machine before I could take note.

Got my hands on it again today, cleared the codes and went for a drive. Checked after the drive and the following was logged

P040C exhaust gas recirculation temperature sensor A circuit low

Can't find much reference to the c code here, only the d code. They obviously relate to the same thing, only one is circuit high and one is circuit low. No warnings or bongs from the dash, is this just a ghost code?

Not sure about ghost code, but I have just changed one of these for exhaust gas temp to high reading. The job ended up going pear shaped requiring removal of the N/S manifold to get it out, 2 day job to do it, of a job including diff out and turbo off. Be careful not to break it if you change it. They snap off relatively easy leaving you with no option but a strip down. Had to use drill and heat once off to get it out.
A new manifold is circa £500

The reason I ask is that mine is still under LR warranty so was going to poke them about any existing fault codes when it goes in next month but I'd read on another forum that they will not do anything with this (specifically the D code) under warranty as it's not raising an EML and iirc their justification was that it does not cause overfuelling and therfore not cause damage to the DPF etc.

Assuming that LR won't replace it and that I don't do it myself (unlikely, I rarely solve more problems than I cause when I get a spanner in my hand) is it likely to be an expensive job... obviously if that manifold has to come off then the answer would be yes, but if all goes to plan?

Maybe I am concerned for no good reason but I'd really like the car to be clear of any fault codes at all.

On the topic of reading and clearing faul codes, does that have any negative impact on warranty status. Info on that seems to be sketchy, certainly reading codes should be fine but clearing codes? Thought didn't even cross my mind at the time, I just wanted to clear down and see what was re-raised.

To be honest, and IMO I would leave well alone if it’s running ok and not putting any lights up, the one I just done passed the MOT emissions test and had not lights on, but the customer who recently bought the car from us had the code read by a friend with test equipment and insisted it was corrected, as he wrongly assumed it was the EGR at fault so we did the job to keep good customer relations more than anything.
I think Cam tech LandRover should be in striking distance for you, if unsure you’ll get no better service than from Craig, he really knows his stuff with RR’s

Cheers buddy, been a while since I was last in a FF and that's was brand new (not mine) but it feels fine, has plenty of poke, seems smooth and just returned 34mpg on a 12 mile gentle run at 40-50mph, so seems fine to me. I'll heed your advice and leave alone

Definitely intending on visiting cam tech when my life here calms down a bit. Seems highly regarded on here so was my plan for ongoing service and maintenance once the LR warranty is out in October.