Need help with P0171 & P0174 on L31 engine
Thread Starter
TECH Apprentice
Joined: Aug 2018
Posts: 383
Likes: 108
Need help with P0171 & P0174 on L31 engine Hello guys ,I'm sort of new and have only posted once. I've got a K3500 5.7 with 206,000 miles that has these 2 lean codes. It was formerly a farm truck, so it's a little rough, but not too bad.
I have checked the fuel pressure and it is around 55 psi.
I had previously changed the fuel filter and air filter. The air filter box was full of straw, lol.
I had gotten an EGR valve code, and pinpointed the EGR valve as faulty. I swapped it into my Silverado and the same code came on that truck, so I bought a new EGR.
Shortly thereafter the P0171 and P0174 came on. I have cleaned the MAF sensor with that special cleaner.
I've been driving like that over the weekends and I also now have P0157 HO2S circuit liw voltage bank 2 sensor 2, in addition to the 2 lean codes.
Here is my freeze frame information:
Calc Load 3.5%
ECT 192F
STFT B1 6.3%
LTFT B1 17.2%
STFT B2 30.5%
LTFT B2 19.5%
MAP 12 (inHg)
Eng RPM 700
Veh. Speed 4 mph
MAF 1.06 (lb/min)
TPS 0.0%
At this point I thought intake manifold gasket and fabricated a crude smoke machine, but it's not leaking at the intake manifold gasket. I do have a small smoke leak at the EGR valve itself and at the intake box going into the valve body. I swapped another EGR and it does the same.
Short of buying a scanner that has live data and cheking the O2 sensors for signal, any other pointers?
It drivIs pretty good. At idle, it has a small vibration, but i don't think it's a miss or anything like that.
I have checked the fuel pressure and it is around 55 psi.
I had previously changed the fuel filter and air filter. The air filter box was full of straw, lol.
I had gotten an EGR valve code, and pinpointed the EGR valve as faulty. I swapped it into my Silverado and the same code came on that truck, so I bought a new EGR.
Shortly thereafter the P0171 and P0174 came on. I have cleaned the MAF sensor with that special cleaner.
I've been driving like that over the weekends and I also now have P0157 HO2S circuit liw voltage bank 2 sensor 2, in addition to the 2 lean codes.
Here is my freeze frame information:
Calc Load 3.5%
ECT 192F
STFT B1 6.3%
LTFT B1 17.2%
STFT B2 30.5%
LTFT B2 19.5%
MAP 12 (inHg)
Eng RPM 700
Veh. Speed 4 mph
MAF 1.06 (lb/min)
TPS 0.0%
At this point I thought intake manifold gasket and fabricated a crude smoke machine, but it's not leaking at the intake manifold gasket. I do have a small smoke leak at the EGR valve itself and at the intake box going into the valve body. I swapped another EGR and it does the same.
Short of buying a scanner that has live data and cheking the O2 sensors for signal, any other pointers?
It drivIs pretty good. At idle, it has a small vibration, but i don't think it's a miss or anything like that.
Lean codes usually refer to a fuel issue. Check the fuel psi regulater. Pull the vaccum line and check for fuel. If so, its a bad regulater. Pretty common on these trucks.
What fuel pressure goin down road? Make a quick pull and verifie pressure doesnt fall off.
Data shows its lean on bank 2 passenger side. I would pull a coil harness 1 at a time and see if it has a miss on tht side. Youll know when u find a bad cylinder tone will change.
What fuel pressure goin down road? Make a quick pull and verifie pressure doesnt fall off.
Data shows its lean on bank 2 passenger side. I would pull a coil harness 1 at a time and see if it has a miss on tht side. Youll know when u find a bad cylinder tone will change.
Thread Starter
TECH Apprentice
Joined: Aug 2018
Posts: 383
Likes: 108
Ok, thanks for the suggestions. I will check the MAF. I believe I watched a video showing how to clean it with Q-tip.
Now, as far as fuel pressure while driving, wouldn't that cause to lean on both banks?
Now, as far as fuel pressure while driving, wouldn't that cause to lean on both banks?
