Need advice and help on code p0171

[Illicitdream]

So I recently changed out my knock sensors and harness with oem ones. I pulled the fuel line and installed new o rings on the fuel injectors as well. Now I'm getting the p0171 code. I have cleaned the maf and ran seafoam through the intake. I also believe I bought the sensor only about a year ago. I have read many different threads on here about the possibilities of what could be causing this code to go off. The truck drives fine and normal. No stuttering or misfire, even under load and hard acceleration. I have not changed the o2 sensor or a/f ratio sensor that is upstream of the cat. My scanner can read the maf and the amount of fuel that is being used. What's the regular numbers? Or what should they be? It reads it as lbs for the air flow and gallons for the fuel. There's no visible cracks or vacuum hose leaks. The gaskets for upper and lower intake were all brand new felpro gaskets. The fuel injectors were cleaned before reinstalling them. Any thoughts?! Thanks in advance...

 

[Jmabry66]

P0171

I feel your pain, my truck is also throwing the P0133, P0130, and on occasion P0125, I believe mine is the MAF as its dumping fuel into the intake and my mileage has gone to crap. I'm going to the Toyota house to have it checked, but from what I have read it's mostly fixed by the bank 1 O2 sensor in front of the Cat or the MAF.

 

[gamefreakgc]

If you get a P0171 after working on the truck, 9 times out of 10 it's a vacuum leak where a gasket was installed wrong or a vacuum line is disconnected. Re-trace your steps. Also, you can try this trick:

<iframe width="560" height="315" src="https://www.youtube.com/embed/9CPqbaSgcok" frameborder="0" allowfullscreen></iframe>

 

[19963.4lsr5]

Clean the MAF sensor, throttle body, and make sure the vacuum line going to the fuel pressure regulator didn't come off pulling the injectors. It's a system too lean code. The precat O2 sensor is what controls this code.

 

[Illicitdream]

If you get a P0171 after working on the truck, 9 times out of 10 it's a vacuum leak where a gasket was installed wrong or a vacuum line is disconnected. Re-trace your steps. Also, you can try this trick:

<iframe width="560" height="315" src="https://www.youtube.com/embed/9CPqbaSgcok" frameborder="0" allowfullscreen></iframe>

Thanks for the feedback. I'm thinking it has to be a vacuum leak as well... The upper and lower intake gaskets were installed correctly, I made sure of that. Looks like I'm gonna have to tear it back apart and re-trace back like you stated. This trick might help me locate the problem though. Thanks again!

 

[Illicitdream]

Clean the MAF sensor, throttle body, and make sure the vacuum line going to the fuel pressure regulator didn't come off pulling the injectors. It's a system too lean code. The precat O2 sensor is what controls this code.

The MAF was cleaned again last night and the throttle body was recently cleaned before tearing it down for the knock sensors. I will check the hose connecting to the fuel pressure regulator. I'm going to tear into it probably this weekend. It's definitely going to throw the code again even though I just resent it last night after cleaning the MAF. I checked on my scanner and its in the system as a pending code. Thanks for the ideas! Tearing it all back apart again!!

 

[19963.4lsr5]

The MAF was cleaned again last night and the throttle body was recently cleaned before tearing it down for the knock sensors. I will check the hose connecting to the fuel pressure regulator. I'm going to tear into it probably this weekend. It's definitely going to throw the code again even though I just resent it last night after cleaning the MAF. I checked on my scanner and its in the system as a pending code. Thanks for the ideas! Tearing it all back apart again!!

What is your LTFT? That is what produces the code. The PCM chooses a fuel map based on sensor inputs. aKa MAF, coolant temp, inlet air temp, TPS position, etc......then it final check is what the 02 sensor sees in the exhaust and makes adjustments to the LTFT to bring the Air Fuel Ratio up to 14.7:1. Even if all sensors are producing the correct input and PCM chooses the correct fuel map if fuel pressure is not correct (too high or too low) the precat O2 sensor will sense that and correct the Fuel trims.

 

[gamefreakgc]

Thanks for the feedback. I'm thinking it has to be a vacuum leak as well... The upper and lower intake gaskets were installed correctly, I made sure of that. Looks like I'm gonna have to tear it back apart and re-trace back like you stated. This trick might help me locate the problem though. Thanks again!

Don't tear it up yet! You can do the check even around the gaskets you removed and pin-point the leak. Most often it's just a loose vacuum hose or perhaps the air intake isn't sitting quite right. Takes all of 5 minutes to check.

I somehow put the throttle body gasket on wrong once. Ran fine but threw codes. Heck, I forgot to put a 1 in. diameter hose on the back of the air intake and it ran fine LOL. Can't kill these engines.

 

[19963.4lsr5]

Spraying brake cleaner or carb and choke cleaner at stuff you removed and listen for the idle to change.