Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Codes p0171 &p0174

i have a 1996 ford taurus lx dohc v6 3.0…i keep getting codes p0171 &p0174 System Too Lean (Bank 1 and bank 2.i check for air links and i did not find any…i never got that code tell i replace the MAF sensor…


Didn’t we talk to you a few weeks ago?

If I recall correctly, I thought the replacement MAF sensor you got is faulty, because the new sensor fixed the rough running, but the lean codes only appeared after the new senor

You might want to check if you have an actual lean condition

Low fuel pressure
Vacuum leaks

I’ll add some more . . .

Don’t assume your fuel pressure is fine, just because the engine seems to be doing okay
I’ve seen engines idle just fine with fuel pressure that was low enough to throw those codes.

Don’t assume you have no vacuum leaks, just because you can’t hear any hissing. I’ve seen countless engines that had vacuum leaks that didn’t cause rough running or hissing.

A fuel pressure gauge will help you sort out any fuel pressure problems

An evap/smoke machine will help you locate any intake and exhaust leaks

Just a note but I put a new (NAPA) MAF on my Buick once and kept getting lean codes on the highway. I finally substituted another identical MAF from one of my other cars, and the problem went away. I returned the NAPA MAF for another one that was ok.

I’m not a NAPA hater, but I’ve gotten a fair share of bad parts from them over the years . . .

But it could just as easily have been Autozone or somebody else, as a lot of the big name parts stores source the exact same parts

The replacement mass air flow can be faulty. Swap it out under warranty and see how it goes. A mechanic with a scan tool can bring a mass air flow sensor into calibration by adding a piece of foil tape to the bottom void space of the sensor. Block more void space until the long and short term fuel trim values when combined are under ten percent.

My friend replaced his MAF and it was bad right out of the box. His made his car not start after he put it in. O’Riely’s part.

The plenum between maf and intake sometimes splits on cars. The flexible bellows splits on the bottom. Or some hard to see place. Some cars are notorious for torn plenums. The maf is mounted to manifold on some cars and flex intake tube on others

These plastic intake manifolds are prone to leaking. Mostly when cold. There’s also a history of the PCV hose practically turning to mush causing a vacuum leak. And if I remember right these have the vacuum operated intake manifold runner control. The intake likes to leak where these shafts pass through.