Po 171 & 174

The Check Engine Light has been coming on and going off on my wife's 2001 Astro for the last month. I finally was able to get by the parts store when the light was still on. The reader showed codes PO 171 & PO 174. The van seems to run fine and I have not noticed any sign of running rough or anything. If anything there might be a decrease in fuel mileage, not sure as I do not drive it much. The store employee said it was probably the O2 sensor. Any way to know for sure? Or, any other possibilities? BTW, the MAF was replaced about 6 months ago because of a code specific to that.

Thanks for any input.

P0171 - System Too Lean (Bank 1)

P0174 - System too Lean (Bank 2)

Since the PCM is reporting a lean condition in both banks, it is not likely a weak sensor, but an actual overall lean condition. Vacuum leaks, low fuel pressure, and an under-reporting MAF can contribute to a lean condition. Since the vacuum hoses are exposed to extreme heat and flexing, they tend to fail in the Astro/Safari sooner than in other installations. It would be advisable to verify the condition of all vacuum hoses, check the PCV valve, and intake duct connections downstream of the MAF.

If the intake and vacuum lines are intake, test fuel pressure, both running and standing (after shutdown).

Thanks for your response. I did some looking per your instructions and found a rubber line that had broke. It is about a half inch diameter line that attaches to the inlet duct behind the MAF sensor. I assume this to be my problem. Either way it obviously needs replaced. I will replace it and hope it solves the problem.

Thanks again.