Some of the reasons for P1151. Bank 2 Upper O2 sensor. You may want to consider cleaning the MAF sensor and changing the O2 sensor.
P1151 - Lack of HO2S-21 Switch, Fuel Trim at Limit The HEGO Sensor is monitored for switching. The code will set when the HO2S fails to switch due to circuit or fuel at or exceeding a calibrated limit.
Electrical:
�· Short to VPWR or VREF in harness or HO2S
�· HO2S circuit shorted to Ground
�· Water in harness connector
�· Open circuit
�· Corrosion or poor mating terminals and wiring
�· Damaged HO2S
�· Damaged PCM (other DTCs should be present)
Fuel System:
�· Excessive fuel pressure (stuck fuel pressure regulator, restricted fuel return lines, etc.)
�· Leaking/contaminated fuel injectors or fuel pressure regulator
�· Low fuel pressure or running out of fuel (fuel pump concern, fuel supply line restrictions, low fuel level, etc.)
�· Vapor recovery system (stuck VMV, etc.)
Induction System:
�· MAF contamination
�· Air leaks between MAF and throttle plate
�· PCV system / Other vacuum leaks
�· Improperly seated engine oil dipstick
EGR System:
�· Leaking gasket
�· Stuck EGR valve / Leaking diaphragm or EVR
Base Engine:
�· Oil overfill
�· Incorrect cylinder compression
�· Exhaust leaks before or near the HO2S
�· Secondary air stuck on
Bank 2 (radiator side) Upper O2 sensor; Need a O2 sensor removal tool, 7/8 inch or 22 mm crescent wrench.
On this 2-Dimensional picture, ignore the red box and arrow, the Bank 2 Upper is the sensor on the left of the pre-cat (closest to the oil filter). The arrow is pointing to the Bank 2 pre-cat
Originally posted by chongo:
Click Duratec Maintenance FAQ for most how to items.
. As suggested, do post the exact code(s) and take pictures. There is a good chance the MAF sensor is not put in a proper spot. And it probably needs to be cleaned anyway.
