my 03 4.7 is throwing an error message- p 0171. system too lean, bank 1. black smoke is coming from my exhaust constantly at idle (too much fuel) and when i get down into it. with T.S. Ernesto coming through last week, the roads were flooded beyond belief. i went through a puddle almost up to my doors at little more than idle speed, with the short-shaft fan clutch from auto zone i put on, the fan isnt even in the shroud, about 1/2-1 inch from the pulleys. i think it threw water into the intake and it sucked it into the motor. as a result i think it burned out the upstream o2 sensor therfore computer A/F ratio is thrown off and causes black smoke because its just dumping fuel into the motor. could it really be the o2 sensor? the error message doesnt say anything about o2 sensor, but upstream one controld A/F ratio from what i gather. i just cant stand the smoke from the exhaust and the 8 mpg it brings. usually i get 14-15 in the city. one thing after another with these trucks......damn. anyway my ? is should i replace the o2 sensor?