I have already replaced the MAF sensor, but my fuel efficiency remains around 12 miles per gallon and the check engine light is still illuminated. The light occasionally turns off, but it's mostly on. I've ruled out any vacuum leaks. Given this ongoing issue, could the problem be related to the oxygen (O2) sensor? I'm specifically concerned about the P0174 code on my 2001 Nissan Frontier SE with a 6CL 3.3L engine.
Average fuel economy is between 10 and 12 miles per gallon, depending on driving conditions.
Clarification needed: are you referring to the vehicle's total mileage or current fuel efficiency? Also, what is the engine type under the hood?
The engine has approximately 56,000 miles and it's a 6CL 3.3L engine.
Try cleaning the heating elements in the MAF sensor using electrical contact cleaner and thoroughly clean the throttle body. Inspect all vacuum hoses, PCV valve, and other related components. Afterward, reset the PCM. Dirty or faulty MAF sensors are a common issue on Nissan vehicles—especially older models like this one. Let us know how it goes! Good luck.
Could you provide your current average mileage and the exact model year of the vehicle? This helps narrow down potential causes.