I got two ODBII fault codes today - P0171 and P0174 - System Adaptive Fuel too lean (Banks 1 and 2). It sounds like a common fuel or air control element is the problem.

I had a new fuel pump installed a couple of months ago, and that seems to be working OK. Vehicle starts and runs well, and has good power.

So what should I try first - fuel filter, Mass Airflow sensor, upstream O2 sensor...something else???

Can someone give me some advice on what the most likely cause is?

Thanks,

kiteman

 

Assuming you have the 4.0L there are lots of threads/posts for these codes on the forum. Try the "Search this forum" function.

-Rod

 

Vacuum leak after MAF or a dirty MAF sensor, usually