Lean Codes P0171 & p0174 / p1131 & p1151
 

Okay can an exhuast leak cause this codes to pop up sometimes i just get p0171 and p1131. I checked to see if i can find the elbow by the firewall no luck any body know what line to follow or where exactly it would be located.:confused::confused:

Follow the line from the PCV valve.

do we have a diagram im completly lost i replaced my pcv hose so is that it.

YES an air leak after the MAF can cause those codes or an exhaust leak around the o2 will cause them too.

What engine do you have and what year?

its a 2002 4.2l v6

just cleaned the maf sensor and has been off for 70 miles keeping my fingers crossed this was it.

all codes are gone but now i still have p0174 by itself what can this be i know i went under the truck and i have an exhuast leak after the cats could that be it.?

Probably not it is too far down stream.

I'd check for vacuum leaks. Start with the PCV system, you may have the heated PCV on the side of the t/b. The o-ring gets hard on those babies and Ford only sells the whole thing. If it is the o-ring you might be able to get a GM distributor o-ring in the help section at Autozone. Just be sure that it is the oil resistant kind.

Also check the hoses where the plastic pipe connects at each end, they burn through. If all that checks out then check the rest of the vac lines.

You can spray around suspected areas with starter fluid or WD-40 whike the engine is running. If the engine runs different when you spray then you found a leak.

Good luck and post the results.

ok i replaced the o rings like 6-8 months ago and the pcv system on the side of the tb only thing i havent replaced is o2 sensors and i have a major exhuast leak after the cats like a foot away .Can that be it also replaced the dpfe sensor. It's been showing codes p1131 and p1135 and then check it after and the codes will change to just p0174. Im lost and stumped also did the upper intake gasket and bolt change .im only now showing p0174 code.

P0174 is lean bank 2 (driver side) there are 2 vac hoses that go on that side. one is from the brake booster check that line real good. Also how do your brakes work? You can get a lean code from a bad brake booster too.

The other vac line is for your vapor management system, a bad vapor management valve can also cause that code. There is a vac line that goes from the plenum to the vmv on the firewall, check that one good too. Then follow the metal pipe that goes back to the tank and there is a small section of hose in the wheel well behind the front tire on the driver side. That piece takes a beating from road stuff, if it is flaky change it.

Last suggestion is on the passenger side by the starter solinoid there is a "T" and another short piece of vac hose check that guy too. After the "T" the line continues to the box behind the battery, check the box for cracks.

You put 1131/1135 as the other codes I'm guessing 1135 is a typo and you meant 1134. Those codes mean the rear O2's aren't switching, the PCM is trying to trick the front O2's out of the lean condition. Fix the 174 and I think the others will go away.

Good luck and post back.

ok i did check the t and no cracks. now where is the vmw do we have a diagram or pic . Also exactly where is the metal line you say. no it wasnt a typo i did also got p1135.

The VMV is on the fire wall next to the brake booster (driver side) There are 2 larger and one small lines going to it, one is kinda "s" shaped and goes to the plenum. The other kinda comes out the bottom and goes to a metal line and drops down to the frame rail. Right where it turns to go back to the tank there is about a 75 degree fitting and then a piece if hose about an inch to inch and a quarter long. That is the one I'm talking about. Also in the vapor system there is a bunch more back by the tank above the spare tire, I think those might be a real long shot for this issue tho.

thanks i will check those tommorow but just an fyi i think it might be my o2s reason being i replaced my cats like 3 4 months and never have i replaced the o2s but i will check those.

You need to replace your upper intake plenum bolts and gaskets.

Those babys are about $50-$60 each. If they are reporting a problem they are probably ok. I've got over 147k on mine, went thru the 171/174 and replaced the gaskets and bolts and never did a thing with the O2's. But you could be right.

Did you do the starter fluid thing to check for leaks, or just look? This is where the spray stuff works good.

Good luck and post back results.