ericspkl

hey folks.

99 cherokee 4.0L

coming down from silver star mountain (WA state) today and after i had been back on paved roads for 5 miles my check engine light comes on

went to the auto parts store and its throwing me code p0171.
i did a search already and it seems as though this code gives everyone alot of trouble with MPG's and idle quality.... but my jeep seems to be acting fine, even WITH the code.
idle is fine (maybe a little rough...)
MPG's seem fine

im assuming is an O2 sensor.
i got under the jeep with a flashlight and looked for cracks in the exhaust line anywhere in front of the sensors but i didnt find anything
i dont really know how to check for vacuum leaks..
i dont think the exhaust manifold has a leak but i could be totally wrong.

i was on gravel roads today going 25-35mph, and quickly after (on pavement) i was going 50-60. Maybe could a rock have come out of my tread and hit the exhaust pipe or sensor or....something like that? i would like to avoid taking it to the shop if i can fix it myself.

any help or suggestions would be appreciated!

CCKen

P0171-1/1 FUEL SYSTEM LEAN

When Monitored: With the engine running in closed loop mode, the ambient/battery temperature above 20 deg. F and altitude below 8000 ft.

Set Condition: If the PCM multiplies short term compensation by long term adaptive and a certain percentage is exceeded for two trips, a freeze frame is stored, the MIL illuminates and a trouble code is stored.

Possible Causes:

INTERMITTENT CONDITION
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
FUEL PUMP MODULE
O2 SENSOR
O2 SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
O2 SENSOR HEATER OPERATION
TPS VOLTAGE GREATER THAN 0.92 VOLTS WITH THROTTLE CLOSED
TP SENSOR SWEEP
MAP SENSOR OPERATION
ECT SENSOR OPERATION
ENGINE MECHANICAL PROBLEM
FUEL FILTER/PRESSURE REGULATOR (HIGH)
PCM

Also: Clogged Catalytic Converter, Dirty Fuel Injectors, Vacuum leaks from intake manifold or hoses.

First, check the O2S Heaters fuse in the PDC. Looking at the open PDC from the front of the Jeep, the O2S heaters fuse is a 15 amp fuse, located in the top row of mini fuses.

Smockmock

I had same code and o2 sensor worked for me.