2007 tucson 2.7ltr.Lean codes both banks. Already checked the tsb for the air box and it has the correct part installed. Found an obvious vacuum leak at drivers side of intake at the gasket for the plenum air diversion plate. thought for sure this was a direct hit for a shared lean code problem on both banks.. Gasket not available seperately. Had to replace entire upper intake assembly ( not cheap). No running complaint from customer. Codes returned 2 days later...help.......

bank 1 sensor 1 lean code. Check vacuum lines first. Could be egr leak also. Most vacuum lines run on the back side of the engine on these. Most common fail is the PCV 90 degree elbow. On the passenger side.

I will try to paste an article for you. Several sources indicate this is a Bank 2 O2 sensor problem and that it is failing to switch and adjust for the fuel mix. But as you can see, many defects can lead up to this O2 sensor Code 1150.

I would try to use a spray bottle of water and go around the Intake manifold and spray the water while the engine is running. An intake leak will draw water into the engine and change RPM.

If no success then try changing the O2 bank 2 sensor. You may need to wipe the computer and clear the Code. H40 DTCs P1131, P1132, P1151 AND P1152: UPSTREAM HO2S NOT SWITCHING. DTC P1130: FUEL SYSTEM NOT SWITCHING AT FUEL TRIM (RICH OR LEAN)
Diagnostic Trouble Codes (DTCs) P1131 bank 1 (Cylinder 1) and P1151 bank 2 indicate the fuel/air ratio is correcting rich for an overly lean condition. The HO2S voltage is less than 0.45 volt. DTCs P1132 bank 1 (Cylinder 1) and P1152 bank 2 indicate the fuel/air ratio is correcting lean for an overly rich condition. The HO2S voltage is greater than 0.45 volt.
DTC P1130 and P1150 indicate the fuel control system has reached maximum compensation for a lean or rich condition and the HO2S is not switching.
DTC/HO2S Reference List
•HO2S-11 = DTCs P1131, P1132 and P1130
•HO2S-21 = DTCs P1151, P1152 and P1150
Possible causes:
Fuel system
•Excessive fuel pressure.
•Leaking fuel injector(s).
•Leaking fuel pressure regulator.
•Low fuel pressure or running out of fuel.
•Contaminated fuel injector(s)
•Vapor recovery system
Induction system
•Air leaks after the MAF.
•Vacuum leaks (vacuum lines and gaskets).
•Restricted air inlet.
•PCV system.
•Improperly seated engine oil dipstick.
EGR System
•Leaking gasket.
•Stuck open EGR valve.
•Leaking diaphragm.
Base engine
•Oil overfill.
•Cam timing.
•Cylinder compression.
•Exhaust leaks before or near the HO2Ss.
•Check intake air system for leaks, obstructions and damage.
•Check air cleaner element, air cleaner housing for blockage.
•Verify integrity of the PCV system.
•Check for vacuum leaks. )

Lean on Bank 2 means one side of the engine is getting less fuel or too much air. I also own a 4.0L and I work on these models for this code consistantly. Usually if you have a vacuum leak at the pcv valve hose behind the throttle body you will get a lean Bank 1 and 2.
My recommendation in these cases would be to change the PCV valve (helps with your gas milage) and the fuel filter; other than that you will have to be sure the fuel pressure is correct and there is no vacuum leaks on the driver side of the engine. I am 90 percent sure the fuel filter, pcv valve and clearing the codes will correct this issue.

Here I find one TSB...
MALFUNCTION INDICATOR LAMP (MIL) ILLUMINATED - SYSTEM LEAN DIAGNOSTIC TROUBLE CODES (DTC'S) - SERVICE TIPS

FORD:
2000 Contour
2000-2002 Escort
2000-2003 Escort ZX2
2000-2004 Crown Victoria, Focus, Mustang, Taurus
2002-2004 Thunderbird
2000-2003 Windstar
2000-2004 Econoline, Excursion, Expedition, Explorer, F-Super Duty, Ranger
2001-2004 Escape
2004 Freestar
2000-2004 F-Series

LINCOLN:
2000-2002 Continental
2000-2004 LS, Town Car, Navigator
2002-2003 Blackwood
2003-2004 Aviator

MERCURY:
2000 Mystique
2000-2002 Cougar
2000-2004 Grand Marquis, Sable, Mountaineer
2004 Monterey

ISSUE: This article is intended to aid in diagnosing DTC's P0171, P0174, P1130, P1131, P1150, P1151, P2195, or P2197 (system lean or lack of HEGO switches) when a vacuum leak is present. HEGO sensors, MAF sensors, and PCM replacements are not an effective repair when a vacuum leak is causing the above DTC's.

ACTION: Perform the following inspections/repairs when the above codes are found in memory. Procedure provides instructions on how to make comparisons of the total fuel corrections (using scan tool or equivalent) at idle and high RPM's to help determine if a vacuum leak is the root cause of the DTC's.

SERVICE PROCEDURE:
NOTE FREEZE FRAME AND ADAPTIVE FUEL VALUES (ASSOCIATED WITH "LONGFT" PID) WILL NOT BE AVAILABLE IF A KAM OR OBDII RESET WAS RECENTLY PERFORMED.

NOTE FREEZE FRAME DATA WILL INDICATE THE ENGINE AND AMBIENT CONDITIONS WHEN THE DTC WAS SET. THESE ARE IMPORTANT BECAUSE THE VACUUM LEAKS MAY OCCUR ONLY WITHIN SPECIFIC TEMPERATURE RANGES AND MUST BE DUPLICATED TO DETECT THE LEAK.

NOTE FUEL TRIMS AT IDLE ARE PARTICULARLY SENSITIVE TO VACUUM LEAKS SINCE THE UN-METERED AIR LEAKAGE FLOW IS A HIGHER PERCENTAGE OF TOTAL AIRFLOW AT IDLE THAN AT PART THROTTLE. THE BAROMETRIC PRESSURE (BP) PID IS NOT RECOMMENDED TO VIEW WHEN DIAGNOSING A VACUUM LEAK. BP IS AN INFERRED PID CALCULATED DURING HIGHER ENGINE LOADS.

too lean on bank #2, usually a vacuum leak (hose or intake manifold), also check/clean your Mass Air Flow meter. There is a Technical Service bulletin on this issue too:

http://www.aboutautomobile.com/TSB/2001/Toyota/Highlander/Others

it may or may not apply, but further investigation is warranted-look for the obvious items first (up top).

Not a Generic Code

MFG Specific

P1151---Lack of HO2S-21 Switch,
Sensor Indicates Lean


O2 Sensor trying to correct for a rich condition,
thus goes lean

I have 27 Possible Causes in the Diagnostic
trouble Code Chart

Common DIY

Worn out Sensor
Too Much Fuel Pressure,doubt that
Leaking Injector,maybe
Vacuum leaks on ducting from air filter to throttle
PCV Leaks
Oil dip stick not sealed
Egr ,issues
EVAP System leaks

H40 DTCs P1131, P1132, P1151 AND P1152: UPSTREAM HO2S NOT SWITCHING. DTC P1130: FUEL SYSTEM NOT SWITCHING AT FUEL TRIM (RICH OR LEAN)

Diagnostic Trouble Codes (DTCs) P1131 bank 1 (Cylinder 1) and P1151 bank 2 indicate the fuel/air ratio is correcting rich for an overly lean condition. The HO2S voltage is less than 0.45 volt. DTCs P1132 bank 1 (Cylinder 1) and P1152 bank 2 indicate the fuel/air ratio is correcting lean for an overly rich condition. The HO2S voltage is greater than 0.45 volt.
DTC P1130 and P1150 indicate the fuel control system has reached maximum compensation for a lean or rich condition and the HO2S is not switching.
DTC/HO2S Reference List

• HO2S-11 = DTCs P1131, P1132 and P1130
• HO2S-21 = DTCs P1151, P1152 and P1150
Possible causes:
Fuel system

• Excessive fuel pressure.
• Leaking fuel injector(s).
• Leaking fuel pressure regulator.
• Low fuel pressure or running out of fuel.
• Contaminated fuel injector(s)
• Vapor recovery system
Induction system

• Air leaks after the MAF.
• Vacuum leaks (vacuum lines and gaskets).
• Restricted air inlet.
• PCV system.
• Improperly seated engine oil dipstick.
EGR System

• Leaking gasket.
• Stuck open EGR valve.
• Leaking diaphragm.
Base engine

• Oil overfill.
• Cam timing.
• Cylinder compression.
• Exhaust leaks before or near the HO2Ss.
• Check intake air system for leaks, obstructions and damage.
• Check air cleaner element, air cleaner housing for blockage.
• Verify integrity of the PCV system.
• Check for vacuum leaks.

P0191 is Fuel Rail Pressure Sensor "A" Circuit Range/Performance
P2196 and P2198 are lean bank 1 and lean bank 2. You normally show lean bank codes if the air-fuel ratio is not correct. The most common cause is a hole in the hoses between the PCV valve and the intake on the motor (back of the motor generally). The fuel rail pressure sensor code could either be caused by the vacuum leak or by a failing fuel regulator. I would first check for holes in the rubber hoses especially where there are right angle rubber hose connectors. Look for soft squishy or oily spots on the hoses.

you nead to check all you vacuum lines for leaks it sounds like you have a vacuum leak or the o2 sensor is going bad on bank 1 **** i still say vacuum leak

The lean condition is caused from the upper intake gaskets and isolation bolts not sealing properly due to time and poor sealing qualities from the factory ther was a service bulliten for this through ford to replace the gaskets,bolts,vaccum line,and lh side valve cover for this concern the oil was getting onto the rubber contaminating it causing a vaccum leak. If you never had the tsb done i would start there, also if there is high milleage on the vehicle i would also clean the maf sensor and resedt kam.