Please Help! Erratic temp gauge + p2015 B8 A4

[Audiandchill]

Hello Audi family,

I recently purchased a 2011 Audi A4, a few issues, the temp gauge is very erratic, it has never gone over the middle line thankfully. While driving Im at around 70-75 Celsius, sometimes at idle the needle goes back to the middle. But as we speak Im currently idle and its at the same 70 celsius that it is when driving. That is whats throwing me off, I was about to order the water pump/thermostat until now when I noticed the needle not going to the middle at idle. Im still leaning towards a sticky thermostat but Im wondering if anyone else has experienced these symptoms and found it to be a Radiator or something.

I also suspected a coolant temp sensor because of the check engine light, but I believe it’s unrelated as the codes I pulled were P2015 and P0420. Any advice is most appreciated, Im more concerned with the temp gauge but the check engine light is almost equally concerning even though the car drives perfect but it does idle at a slightly higher RPM, Im suspecting I need a new intake manifold but don't want to throw money at parts before hearing from my audizine family, thanks!

[Audiandchill]

Also to add to this, my Heat and A/C work perfectly fine, and the car hasn’t overheated, no coolant loss whatsoever. 2.0t engine 146k miles

[darkme8t]

I had that issue before. When on highway speeds, needle would drop well below center line. On street driving or traffic it would get closer to center, but never above. It was a sticky thermostat. I ended up replacing the whole waterpump/thermostat assembly and issue was resolved.

[Audiandchill]

I had that issue before. When on highway speeds, needle would drop well below center line. On street driving or traffic it would get closer to center, but never above. It was a sticky thermostat. I ended up replacing the whole waterpump/thermostat assembly and issue was resolved.

Okay awesome, thats what I thought but wanted to check with the forum before buying parts, do you know how much you paid? I see a kit on ECS tuning but want to make sure Im not overpaying, thanks!