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OBDII Trouble code 0171?

Redsnake

NAXJA Forum User
Location
Tulsa, OK
OK... my check engine light came on and the trouble code is 0171 and I believe this is

"171 The oxygen sensor is saying that the system air/fuel mix is far too lean (too much fuel is being added as a correction). "

Does that mean my O2 sensor needs to be replaced and if so which one or both? My '96 XJ has 209K miles and I've owned it since 124K miles and have not replaced either of the O2 Sensors. Any other suggestions?

I've had a miss start about 2 months back but it's very hit and miss. It may miss and cut out for 5 - 10 minutes of driving but if I park the XJ and turn it off... let it sit for a bit 10-20 min it seems the miss goes away. There really isn't anything too specific for the miss, but it just happens. Any suggestions are appreciated.

Thanks,
Eric
 
i had the same obdII code and similar symptoms on my '96. it had the original o2 sensor as well; i changed it and all is well again. don't worry about the after-cat sensor, it's only there to monitor the efficiency of the converter. if it's not throwing codes i'd just leave it be.
 
It's a lean code, the computer thinks the engine is going lean. Could be anything from bad gas, intake gasket or vacuum leak, plugged fuel filter or weak pump, or an actual bad sensor or circuit problem.
 
OK... more info. I replaced the fuel filter about 2 months back. Checked the fuel pressure and it was good so I assumed the pump was ok and the lines were flowing. Could be a vacuum leak I suppose... since I replaced the header about 1 year back and had a VERY hard time getting the lower bolt to go back in and actually didn't snug it up. All other bolts are tight, but not the bottom one. I don't hear any leaking noises (pops, whistles, etc) but it could still have a leak I suppose... Any easy ways to diagnose that?
 
mine was clearly a bad sensor. it was running way too rich and still throwing a code for a lean system. it ran better with the sensor disconnected after pulling the pcm fuse for a minute. it was the original sensor and @ 169k it needed changing anyway, so i started there and it turned out that's all it was.
 
Follow-up...

I changed out the pre-cat O2 sensor and that has made a bid difference in how my XJ is running. I still get what sounds like a little bit of detonation when my jeep gets hot and the AC is running and I take off f/a stand-still... but it's a LOT less than before replacing the O2 sensor. Plus now my idle is back to normal and idling like it's suppose to.

I wonder if there is some other issue w/the detonation??? Any ideas??? I hate to have to run a higher octane gas w/the higher gas prices, but if that's necessary I'll try it. I did run a bottle of fuel system cleaner thru the lines about 1 month back, perhaps I need to try it again.
 
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