P0174 Trouble Code?

Changed both upstream o2 sensors. Bank one sensor fluctuates much lower milivolts than Bank two sensor. Seems to run to good to have vacum leak.

Thanks, is it possible bank one is running leaner than bank two due to low fuel pressure? Bank one sensor fluctuates from 0 to about 700 on scan tool, bank two fluctuates from about 300 to 800. Both upstream sensors new. Thanks for your reply.

Also downstream sensor one shows lower than downstream sensor two, witch sinals cat is working properly, I think?

Will check fuel pressure, and change filter thanks for tip.

What would cause a PO171 and Po174 code to come up on chevolet suburban

Checked pressure 45 lbs cold start pressure regulator dry and working. Couple lbs low be enough to cause?

3 days ago changed the fuel pump, been runing seafoam in it for the past 3 months, would map sensor cause this problem

What would cause codes PO171 and codes PO174

Chevolet had it for a month and changed the whole month they said that they changed the whole intake manifold

I also had codes p0171 and p0174 so I looked at the intake gaskets and replaced them, also a few vacuum line elbows that I found cracked that went from the fuel pressure regulator to the air intake. And those codes have not come back.

With the MAF connected it would start fine then about 10 to 15 seconds the RPM's would decrease and it sounded like it was ready to stall but really just run rough. The air filter intake hose is secure the connection look good, i've got good PWR in 14VDC and a solid ground, from the signal side with the truck running I get about 5.04VDC. I didn't get the 400 series codes until I changed the MAF. When I disconnect the MAF it runs perfect with no issues.

So you think that the new sensor I put was just bad?