Vw citirox idle problems in gear

[Dakes26]

Hi guys, I’m new to the community, this community is awesome, help me a lot. Still struggling with the navigation of the site hopefully this will get through to the right people. I own a Vw citirox 1.4 I’m having a problem with my idle. My car isles just above 1000rpm but when I’m in gear or when changing gears my rev sits at 2000rpm and will only come back down if I put my clutch in & out again. The diagnostics test gives an error that my heat gauge is faulty? Can this really be the cause of my idling issue or is it my MPS?