got a SES light today had the code checked and it is P0171. I have already cleaned the MAF. My next guess is o2 sensors any help would be appreciacted.

truck is 2002 lariat screw 4x4 5.4L

 

lean code, could be a bad DPFE thats what mine was..replaced the DPFE and the code went off by itself in about 10 minutes...normally over 60k miles or 5 or 6 years old

 

what is a DPFE?my condition says RICH? is that related?

 

Differential Pressure Feedback EGR Sensor

she'll look like this http://rockledge.home.comcast.net/~r...FE_Plastic.jpg

 

It's not the o2 most likely. The sensor is doing it's job reporting a lean condition.

More likely a vac leak. Start with the PCV system. Almost 10 times outta 9 it's the elbow on the back of the plenum.

If you want to throw away $60 or more go ahead and change the o2 sensor, the elbow is about 5 bucks-your choice. Usually that code is not as complecated as you want to make it-but it can be.

Start cheap and simple then go from there.

 

ah yea 5.4 didnt notice that...check the elbow jgger is talking about first

 

ok so it could be a bad pcv valve or elbow then?

 

yea, start by checking the PCV and see if you can feel any leaks. all the way up to the TB

 

ok i prob just get a new pcv valve and a new elbow just to make sure my friends 98 expy 5.4 did this a few months back

 

replaced PCV valve checked vac hoses and the one that runs from the 90 degree bend after the throttle body to that emmisions sensor? above the brake booster, was dry rotted! Im going to the parts store to replace that black hose that looks like its 3/8? in diameter.Im hoping that this fixes it! that hose bout turned into dust getting it off!all other vac hoses looked ok

 

awesome. maybe 3/8..hope you took the hose to make sure!

 

just replaced that hose-not making that tick tick tick noise at startup but the ses light is still on when I had the code checked at auto clowns the readout said somthing about the MAF reading a lean code. talked to a mechanic today at work{I deliver to his shop} he said a vacum leak could cause a MAF code. also it pulled a PO174 secondary code. what I'm wondering is could this mean my MAF is bad? I have THOUROUGHLY CLEANED IT ACCORDING TO THE INSRUCTIONS ON THIS SITE!!

P.S I DID TAKE THE OLD HOSE TO MAKE SURE!!

 

Did you check the elbow on the back of the plenum and the hose/pipe for tje PCV as mentioned earlier?

Also you did have the codes cleared after you replaced the hoses-right? If you didn't the light won't clear for a few drive cycles.

Another thing to check is the big tube that goes from the air cleaner to the throttle body for splits or holes. It's sucking extra air from somewhere.

 

Sounds to me like he's not getting it.


Tell us CLEARLY what you checked on the PCV system. You have to pull it completely off. Follow it all the way back , remove EVERY last piece.

 

I have followed every hose that is attached to the TB all the way around, PCV all the vac hoses with the engine running and felt for a vacum loss. the only hose that I have found is the one that I have already replaced.I did notice that it would make that tick vac. noise more cold than warm. I will listen again for vac noises when I go to work today, the big plenum after the maf is fine no leakes sprayed soapy water on it last night and took the whole ting off and checked thouroughly.