Thekid96

I have an 02 Silverado 1500 with 218k miles, during cold months the service engine soon light comes on. I had the codes read and it came back as "fuel trim system lean bank 1 and bank 2". I did a little research and came up with the 02 sensors needed replaced. I replaced all 4, both upstream and both downstream, earlier this week. The last few days when I start it for the first time in the morning it idles rough, the rpm goes up to 1500 and drops to down around 500. It'll fluctuate like that for a few minutes. Once it's warm and I drive it, it runs and idles fine. Do I need to reset the ECU after changing the 02 sensors?

tech2

no
when both banks are lean it is most likely a fault they effects both banks. highly unlikely separate pre cat 02 sensors go bad at the same time. the rear 02 sensors are not used for fuel metering but for cat operation diagnostics.
02 sensors signals are ignored during cold start up until the 02 heaters bring them to temp. 30 seconds to 1 minute.
you need to see at what rpm the leak codes are setting. if it occurs only at idle...you may have a false air leak ie leaking intake manifold gaskets, loose air snorkel clamps or vacuum or pcv hose cracked

when you start a vehicle in the morning...its cold...needs more fuel...false air leak...ie air that enters the engine but is not measured by the maf...will cause a lean condition. when warm you don't need such a rich mixture so it runs better.

if you have a scan tool view fuel trim on both banks...if its adding at idle +10% but under 10 at 2500rpm...you have a vacuum leak. if its lean at both speeds..check fuel pressure.