Trouble Code
 

I have a PO171 system too lean code that just came on. Is there anything I can do besides replace the O2 sensor to see if the code will stay off?

Thanks

RE: Trouble Code
 

Im workin on the same prob right now. Do you have the P0174 dtc as well? I have both codes. Too much O2 in the exhaust is the problem. First, clean your maf sensor, then check fuel pressure. When my truck warms up it stops, but when it is cold, the idle is erratic and I have a hesitation/surge on when starting from a stop.
I did the propane trick to check for vac leak and nothing. My fuel pressure is 50-52psi. It should be 55 to 62psi. Im gonna change the filter today cuz installing a fuelshut off valveon the injection return looks like a total pain and I dont have the fancy quick disconnect shut off valve anyway. All this has to be done to check the fuel pressure regulator. Im hoping it is just the fuel filter. Changed it at 85,000 now I have 178,000.

RE: Trouble Code
 

just the one code is coming on.. i haven't had time to work on it but I will clean the maf sensor and replace the fuel filter first.

RE: Trouble Code
 

I'm curious what year is your truck ande what model?
Thanks,
Don

RE: Trouble Code
 

01 xtra cab 4 door 1500

RE: Trouble Code
 

Update. The evap purge valve oring might be bad. I shoot some propane over the valve and the engine idls evens. So I remove it, check the oring and it is blue with some black gunk on it. I clean the oring only to find out it is black with some blue gunk on it. Re installed and the oring seems to fit tight even thought the evap valve is very loose, even when tightened. Gonna replace the oring today.
Does the o2 sensor affect fuel trim? If so a simple exhaust leak could be why it is reading lean, not likely with both banks lean, but the flanges on both sides could be loose or something. Gonna check that too. I guess the o2 sensor could be bad as well.