Originally Posted by Gumby22

P0171/P0174 - Are there any leaks at the exhaust manifolds? If so, those need to be repaired before pursuing other possible causes of these codes. The leaks will allow excessive oxygen into the exhaust stream and skew the sensor readings.

Low fuel pressure is another possible cause. Spec is 50-60 PSI at the rail - should hold for at least a few minutes at KOEO and maintain it KOER at idle. The regulator is part of the fuel pump assembly in the tank.

P0121 - clean the throttle body bore, if necessary. Carbon accumulation around the throttle plate can cause it to stick/drag/bind and intermittent stalling and/or idle concerns can result.

If the TB is clean, monitor the TPS signal KOEO and slowly press the accelerator pedal all the way to the floor and slowly release. Watch for sudden changes in the signal that aren’t the result of your movements. Any sudden changes indicate the throttle body requires replacement.

Originally Posted by Idkchevy1234

Notice my fuel input

Originally Posted by Idkchevy1234

So I got this reading

Originally Posted by mountainmanjoe

you won't . It's part of the pump.
What's going on with your van?

Originally Posted by mountainmanjoe

You need to complete a diagnostic drive cycle

https://www.obd-codes.com/trouble_co...ving-cycle.php

Originally Posted by mountainmanjoe

your fuel level is at 34% And?

Originally Posted by mountainmanjoe

that's "system lean" right?
Many possible causes for that.

It can be exhaust leaks, vacuum leaks, bad injectors, dirty MAF, misfiring, etc. etc.
Yes fuel is one possibility. So verify your fuel pressure with a gauge.

Don't go straight to the parts cannon.
Follow the troubleshooting steps here: https://www.obd-codes.com/p0171