01 XLT 4.6 - service code PO174 - System too lean. Anyone know what would be causing this code. Check engine light has been on for 3 or 4 days. Had the truck scanned at Advance Auto Parts. Could it be bad gas??

 

P0174 is bank 2 lean. If this is the only DTC that is present, check for a vacuum leak along the intake manifold, bank 2. Good luck!

 

Check for an exhaust leak along the bank 2 as well... Try spraying carb/brake cleaner around the intake manifold and watching for an idle change. If you have the ability to watch the O2 PIDs, do so. Try getting the sensor to go rich with propane into the intake to ensure it isn't a faulty O2 sensor that is just reading LEAN...

 

You can also check the PCV hose elbows for cracking as well as cleaning the MAF.