P0171

i was thinking same thing, i spent 5 hours back there replacing exhaust manifold gasket after i couldnt find a crack in manifold. the 02 sensors are reading as they should with the upstream oscillating back and forth and the downstream staying steady above .50.
ive had a manifold leak before and the downstream would ready similar to upstream

was it your purge valve or the valve on the evap canister?

It was the purge valve. I was not clear. Not for this particular car, but for others.

You can discard evap system, by "canceling" the hose which is connected to manifold

I have some known good values for that ecotec 2.4L taken two days ago. Maybe not only watching trim numbers, but more values, we can discover something else.

i'll try anything at this point. i'm going get a new coolant temp sensor just to be safe and because its cheap. i just cant wrap my head around the two different readings from the two different year fuel rails. 2010 injectors have a different part number compared to 2012 and the 2012 injectors work way better. i might do the high pressure pump down the road. someone said that could be it