pennystockart

Hi. new to this forum and would like your input on these 2 codes im getting....usually i get 171 and 174 but this time im getting 151 wich is my first time for this code...i have a 2002 f-150 4x4 sport 4.2L and i live in the northeast....i only get these codes when its cold out..during the late spring, summer and fall, i dont get any codes so its only when the weather gets cold that i have this problem...i know the codes have heated this and heated that in them so is that pointing to my oxy sensors on both banks as the engine is running lean on both sides... thank you and i look forward to your comments....

R&TBabich

The first thing I would look for is a vacuum hose leak causing the 171/174.
A common cause is the PCV hose.
When 171/174 are set both banks are affected. The intake manifold forward to the MAF affects both banks.
I once had just a P0171 and it was a passenger side loose exhaust pipe to manifold connection.
The P0151 is bank 2 and may be just a loose exhaust pipe connection or broken exhaust manifold bolt on the driver's side.

Jbrew

You have a circuit (wiring) issue or bad sensor. Check the O2 harness and connector for the 151. Grey and black wires. The heaters are fine.

pennystockart

thanks..just wanted to ad one more tidbit..when i started it today, there was a ticking noise and it sounds like its comming from underneath on the passenger side exhaust area...does that help in troubleshooting the problem? thank you.

9918939

Wanted to pass on my thanks to the mods on this forum. Getting both lean bank codes, and researching the forum- cleaned out the PCV with cleaner, then did an oil/ oil filter and air filter change (long overdue), then disconnected battery to clean up the terminals-
put the key in ignition and turned to ON position
connected battery
started up, CEL light is out, drove it around a bit, all is good.
Happy holidays to all.

akdoggie

I hope that fixed your problem, but not to try and throw cold water on it, remember that the system doesn't immediately reset. It may take up to 100 miles of driving to reset all the drive parameters. If you didn't put enough miles for the system reset, you may still get a CEL in a few miles. Hopefully you cured your problems and it won't reset.

9918939

Codes came back again - P0171 and P0174. Got some MAF Cleaner-
disconnected NEG
cleaned the sensor and the Temp change sensor
cleaned the PCV valve
hooked it all back up-
noticed (maybe just in my head but) the gas mileage seems to be much better after 50-60 miles of city/ highway.
The stickys helped as me as usual- thanks all.

ericbe45

the 4.2 engine has upper intake gaskets that are a thin rubber style, as milage increases these gaskets become hard and shrink, during cooler weather the concern is enhanced once engine warms these gaskets tend to seal alsoin the bottom of the upper intake are a series of bolts whith rubber seals that act the samw way. might be your issue

9918939

could be- I have the 5.4 and sealed a small coolant leak where the coolant crossover is and no leaks or codes so far.

thanks to the poster who said the MAF should be cleaned at every oil change- good idea! whether its a reusable filter or not. increased my mileage off the bat

thanks all