I had the spanner icon illuminate this morning. Stop car, restart, fine. Some time later it came on again. Forscan gave me some codes which seem to concern transmission  switches. Having done some experiments, Start in neutral and all is well until first is selected. Spanner lights immediately. Start in neutral and select second. Spanner remains off. This looks like a position sensor problem to me but where is the damned thing? 2018 1.0 Ecoboost with six speed manual.

On a Mk8 it should be at the back of the selector arm.  Seen here picture number 6.

https://www.ebay.co.uk/itm/286484810515?

Ford part H1BR-7J066-CA

https://www.ebay.co.uk/itm/297044608710

Thank you all very much. I'd better get my card out!

I tried the number and the search on Ford's site told me it was only £45 but it wasn't compatible. I reckoned that it was but scared of wasting good  money, I resolved to hoik out the battery box and give the offending sensor a Hard Stare to confirm the number. One of the two linkage pivots had a rather strange circlip fitted, different to that on the other pivot. Odd. Somebody must have lost the original, I know not how but by now you've guessed where it ended up!  It was on the magnet on the linkage that runs past the sensor , sending out all the wrong signals. Somebody made a good job of fashioning a circlip at least two years ago. I wouldn't have lost it because I used to work on an aeroplane and we would strip an airframe to the last chip of paint rather than allow a washer to be unaccounted for but I won't be too hard on whoever it was. It might have come off through poor assembly but it went back on tight. I did however lose a spanner. The little yellow one in the Speedo dial and I haven't seen it since! Thankyou Unofix and Tom'sfocus for showing me where to look.