DIABL0

code P0171

My light just came on after i did some towing of my 2 boats. I had my MAF changed a few months back and my 02 Sensors changed not to long ago. Do you think its just a temporary light because of the load of my trailer and boats. I had the code checked at auto zone and the paper also says it could be fuel injectors or ignition misfire. My starter is going on it too does that have anything to do with the ignition misfire?

What do you suggest i do?

Thanks guys!

DIABL0

Anyone?

Marc D

P0171 and P0174 are lean bank codes for right and left banks of the motors. This almost always indicates a vacuum leak. I'd start by looking at the PCV valve hoses and any vacuum lines feeding the intake plenum. Get a vacuum line diagram off Google specific to your motor/year of truck to help you find all the lines. Pay close attention to the factory rubber 90's on the hard plastic lines. 4.2 V-6 motors usually need a new intake manifold gasket to resolve the issue.

akdoggie

What Marc said about the lean codes is spot on. Every week someone has the same question. It is almost always either a bad PCV hose, leaking hose by the throttle body, or some similar vacuum leak. I think that this is probably the most researched code we come across. Also check the intake where they mount. Occasionally one or two will be loose and will cause a lean code to pop up. Good luck.

Warspite

^X3. You can search this forum under Lean Codes - or P071/4 and some curse word after it. Read all of the suggestions, since you may not have all of the symptoms, and one or 2 DIY procedures will address it. Misfires are usually present with bad Coil On Plug (COP), which will throw different codes. Chase one ghost at a time. Good Luck!

BTW, these 2 codes get stored as pending for 20 ignition cycles, so this has been there for a little while. You didn't mention if you have poor idle, and most of the other indications that go with a vacuum leak; the #1 cause of those codes.

ueww40

I am having the same problem and I already posted my problem thread p0171. The frustrating problem with most of the replies is that they always address a generic situation of having codes 0171 AND 0174. What if you get ONE code p0171 only? This will eliminate a lot of the suggestions presented here, because they would affect both banks. My PVC valve and its vacuum line checks out fine. I sprayed starter fluid around the 4 intakes of bank 1 and the rpm does not change. I don't think I have a leak issue here, but what else could be that would affect bank1 only?

biglee88

Had this happen In a economies van with a 5.4 it was caused by the fuel system being contaminated with rust from the gas tank rotting pull fuel filter and check it for rust

ueww40

biglee88, wouldn't bad fuel affect all banks and related components and give both codes p0171 and p0174. In my case I only get the p0171 code and nothing else

biglee88

It would but it won't be as pronounced the only things to affect one bank is pretty much fuel injectors or intake gasket

ueww40

Cleaned the MAF sensor today. Btw at first I could not find it. The sensor is not where you would expect it to be namely in the TB. It is right behind the air filter in the big plastic housing. Replaced the fuel filter and added injector cleaner to the gas tank. I do not suspect injector problems because the engine actually runs rather smooth. I checked for leaky intake again by spraying starter fluid around the intakes where they mount to the block. No noticable change in engine behavior. I did reset the OBD and now I will have to wait to see if any codes come back.