The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Code P0174 &P0171 65 miles after LS Swap installed.

clinebarger · 05-19-2016, 08:42 PM

What I do is....Scan the PCM for High LTFT & STFT readings (Lean) with he engine running, If they are high +15 or higher.......Unpin the Yellow wire from the MAF, Start the engine (It will set a P0101) & monitor the Long & Short Fuel Trims, If the fall back to Zero +/- 5....Suspect a faulty/dirty MAF OR the MAF in the wrong/bad location, My Camaro set lean codes using a stock tune truck PCM because where the MAF is located about 6 inches forward of the throttle body. A custom Tune fixed mine, If the same is true for you....Relocate the MAF closer to the stock Truck location.

If unpinning the Yellow wire has no effect on LTFT/STFT in closed loop, Suspect a Vacuum Leak.

Running open exhaust will also cause a Lean reading by the O2 sensors.

05-19-2016, 08:42 PM	#2
clinebarger Senior Member Join Date: May 2009 Location: Fort Worth, TX Posts: 6,370	Re: Code P0174 &P0171 65 miles after LS Swap installed. What I do is....Scan the PCM for High LTFT & STFT readings (Lean) with he engine running, If they are high +15 or higher.......Unpin the Yellow wire from the MAF, Start the engine (It will set a P0101) & monitor the Long & Short Fuel Trims, If the fall back to Zero +/- 5....Suspect a faulty/dirty MAF OR the MAF in the wrong/bad location, My Camaro set lean codes using a stock tune truck PCM because where the MAF is located about 6 inches forward of the throttle body. A custom Tune fixed mine, If the same is true for you....Relocate the MAF closer to the stock Truck location. If unpinning the Yellow wire has no effect on LTFT/STFT in closed loop, Suspect a Vacuum Leak. Running open exhaust will also cause a Lean reading by the O2 sensors.