So my "service engine soon" light came on the other day. I ran the codes and got a p0171, system too lean on bank 1. I read that this could be caused by a bad MAF sensor, bad oxygen sensor, clogged fuel filter, clogged/bad injector, or a bad/misfiring plug.

My plugs are new as of 20k miles ago, the fuel filter is fairly new as well, i've been told its probably not the MAF because both banks would be lean, so i'm thinking its either an injector or the oxygen sensor.

My oxygen sensors haven't been touched since 30k and i'm at 80k so I think it's worth a try. I was told to try swapping the two sensors between bank 1 and bank 2, then see if the error code changes from bank 1 to bank 2.

Does anyone have some pictures, a how-to, or some instructions on how to reach these suckers?

Tony

 

You should check for vacuum leaks.

 

search this code on here, several people have had this issue including myself

 

before you do all that o2 stuff clean your maf first. thats what was wrong with mine. go to your local Radio Shack and get a can of spray tuner cleaner, #64-4315, and spray it on there. some body else told me to do it on here. than go to auto zone and get it cleared. my light hasn't been on since.

 

After you get done trying everything recommended and you Still have the code. Do what I did after months of trial and error.

Pull the Supercharger and replace the vacuum line on the back of the lower intake manifold.

while you are at it, Clean everything including the exchanger, replace your plugs, and be happy!

PM me and I will go into more detail

 

Well I pulled the MAF sensor and cleaned it, I dont think it is the problem. I also dont think it is a vacuum link since i'm only running lean on 1 bank and not both. I couldnt find a good pictures out there of possible spots to check for vacuum leaks. I dont have a second car so i'm hesitant to pull the supercharger just to look for a leak that might not be there.

I read on here that it might be worth it to swap the oxygen sensors and see if the code moves to the other bank. Does anyone have pics of how to get to these oxygen sensors? Do I have to remove anything else to get to them?

 

There are 4 O2 sensors... the way I understand it, only the ones before the cat are the one's you need to worry about.

The passenger side is a pain... I saw no way to get to it other than loosening up the exhaust. Not a lot of fun if you are doing this on the floor in your garage. I too replaced them and my code didn't go away.

Just to let you know... P0171 was all that I was pulling and it was the small vacuum tube on the back of the lower intake.

I beat myself silly trying to use logic thinking that it would throw both codes (P0171 and P0172).

The mileage you have on the truck is about right too. If you don't find it and end up pulling the SC & upper intake off, you will be amazed at how crappy that little elbow tube is. Mine just fell apart.

Good luck...

 

Is there any way to reach back there or visually check that vacuum tube on the back of the lower intake?

I dont have the garage or tools or time to pull the supercharger. My luck, I would break something else in the process.

Does anyone have pics of this?

 

It's really not that hard to do and you can do it in a day if you stay focused.

There are four bolts on the back of the upper manifold and a couple of those were a real pain. I dropped on in the valley under the lower manifold and never found it.

Not much to break and if you have a digital camera... take pictures when you take it off and then you will have it for putting it back together again.

I've got shop manual instructions for taking it off and replacing it if you need them. Let me know.

If you have some one near you that is a fellow L owner do both of them, yours first and then the other another day. It helps to have and extra set of arms and hands.

I know of no easy way to look at or inspect it. My hands just could not fit back there. Besides... it rots out on the bottom of the elbow and sits right above the transmission bell housing.

I had found some pics on the net and I may have saved them. I'll look later and post them when I find them.

 

Turns out it was a dirty MAF. Problem solved.

 

COOL!!!

I bet it wasn't a dirty MAF though. I think the steps you went through to clean you more than likely stumbled on a vacuum leak and by reassembling the MAF... you took care of the leak.

Let me know if the code pops up again.