Hello, everyone I had a question to see if anybody has experienced this so far. I have a 2019 GMC Sierra 1500 At4 model. I was getting fluctuation with my outside temperature readings from my ambient air sensor eventually causing my check engine light to go on. I have had it at the dealership for about 2 weeks. They have reset the e c m, replaced the wirin harness for the ambient air sensor and also the ambient air sensor. I am still having this issue, has anybody seen this? My local dealership obviously can not figure this out.

Take it to a shop that does electrical. Forget the dealer as soon as the factory warranty ends.

I agree with carfixer007 ^^^^^^^

It is extremely rare to find a dealership that can diagnose anything unusual any more.

When it fluctuates, how much does it fluctuate?

All the way from 40'* to teens in the matter of 3 seconds. But there is no consistency of when it happens. It'* completely random.

Find the sensor and do a visual and see it the harness is solid. If so maybe do a bit of wiggling while someone monitors from inside.
These sensors are usually located at the grille area.