Recently my check engine light came on. Turns out it's my O2 sensors. I have an aftermarket cold air intake and exhaust on it. Which have both been on for almost a year. I was wondering if my mass air flow sensor could be causing the O2 sensor to be reading wrong. Could the mass air flow sensor just be dirty? That's what the guy at Auto Zone told me.. but half the time I don't think they know what they're talking about. Just wanted a few different opinions. Thanks!

 

What were the exact code numbers? Also need year, make, model, engine size.

 

If I remember correctly, they were P0171 and P0174. It's a 2004 Ford F150 5.4L

 

If those are the codes, that is more than likely from a vacuum leak. Those codes are for lean exhaust on both banks. it probably has nothing to do with the O2 sensors. Check the following little list. This is from the Ford manual. Let us know if more info is needed. It is possible the MAF could cause the codes, but it is usually due to a vacuum or air leak after the MAF sensor.


CARRY OUT A VISUAL INSPECTION ON THE INTAKE AIR SYSTEM AND ALL VACUUM HOSES
Check the intake air system for leaks, obstructions, and damage.
Inspect the entire length of all the vacuum hoses for:
proper connections
damage or cracks
damaged or cracked vacuum tees
Verify the integrity of the positive crankcase ventilation (PCV) system.
Verify the proper PCV valve part number.

 

I looked over all my vacuum hoses and did a complete run through on all the wires throughout the engine. Nothing seemed to be out of order. Shortly after I did that my check engine light went out. Should I still look into what the problem was? Or is it possible there was just a glitch?