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Code Issue

(2004 Ford F-150 Heritage)
in Atlanta, GA on November 20, 2009
I purchased 2004 F150 Heritage and have the po 174 code. It says system too lean bank 2. I don't know what that means and would like to get some advice as to what to be checking so troubleshoot the right areas first.
Displaying 2 answers & 1 comments
Popular Answer
A lean code bank two can be caused by a vacuum leak from a vacuum hose or intake manifold that effects bank 2 (ie the bank that does not have number 1 cylinder on that bank). Many automotive repair shops have a machine that generates an inert non flammable low pressure smoke that looks similar to cigar smoke. The intake manifold is sealed off, and smoke is put into the engines intake manifold. The smoke then fills the engines crankcase and if there are any vacuum leaks from gaskets, hoses, or housing smoke emits from the source of the leak. Some mechanics will use propane or aerosol carburetor cleaner, with the engine running they will spray the cleaner or propane around the intake manifold and vacuum hoses. A leak will cause a "lean mixture" condition, when the flammable fuel (carburetor cleaner or propane) comes in contact with the source of the vacuum leak the engine idle speed will raise as the engine has received "fuel". this method of finding a vacuum leak works but is not recommended as it can easily cause a fire.
Lean codes are often falsely set due to an Oxygen senor (or Air fuel ratio sensor ) that is failing, contaminated or gone lazy. Sensor testing requires a scan tool or oscilloscope. When a code is set valuable information is stored in the computer on your car that may require a professional quality scantool to utalize that information. The key information obtained here is it will tell you in a percentage the fuel trim values long term and short term for each bank of cylinders. For example bank one -2% bank two +24% would mean the computer sees it has to add 24% fuel to make the bank two work efficiently.
on January 23, 2011
man i wish i would have found this post sooner!!! i was misinformed, i kept getting system too lean bank 2, finally found a shop that hooked up there scanner to my 2004 ford f150 4.2 v6---system to lean bank 2 sensor one. i looked in my haynes repair manual for hours to find out what bank 2 meant and which sensor and found no such information.I was told by a mechanic and the autoparts store that bank 2 meant it was post catalytic converter and that the sensor i needed was the one on th passenger side post caty converter.spent 2 hours in 13 degrees and 50 bucks on a new sensor only to have the service engine light pop back on 30 miles down the road. From your post i gather that bank two (facing the truck is on the drivers) side and sensor one is the one right off the exhaust and learn i suppose.ANY info would be greatly appreciated. thank you
on February 22, 2010
We just cleaned the MAF with the electronic cleaner and it fixed this problem. Got in, started the truck and the check engine soon light did not come on. FIXED!
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