P0171 Code

[mjonesjr84]

I've read just about every post on this topic before posting.

My 2000 4.0 with 197k miles is giving me a P0171 code. I have already replaced the Bank 1 O2 sensor with a Walker O2 sensor and am still getting the code. I can't find a vacuum leak (fixed the one for the cruise already, Torque is showing good vacuum). It doesn't have any acceleration issues. I've not checked fuel pressure as I'd think if that was it, it would give the code for bank 2 being lean as well.

Any ideas what to check/replace next?

 

[Mac57]

I'd start by replacing the Walker brand O2 sensor with a MOPAR or NGK one. Our Jeeps are very picky with these sensors, off brands perform poorly.

 

[mjonesjr84]

I'd start by replacing the Walker brand O2 sensor with a MOPAR or NGK one. Our Jeeps are very picky with these sensors, off brands perform poorly.

NTK are non existing right now. From what I read in the "Official O2" sensor post, Walker and Denso were a good alternative.

I did just do the PCM reset procedure. Getting ready to run to town so we shall see.

 

[AndyA]

After I replaced my O2 sensors with NGK/NTK it was nothing but error codes until I reset the PCM. Andy

 

[mjonesjr84]

After I replaced my O2 sensors with NGK/NTK it was nothing but error codes until I reset the PCM. Andy

I just replaced the Bank 2 upstream since it came in finally. I did the PCM reset while I changed it.

 

[mjonesjr84]

I think I figured out the problem. The plugs are 1-6 left to right. They were only in the Jeep for about 2k miles. I also noticed this in my garage floor after letting it warm up this morning. I swapped the plugs for a set of APP985's and changed the coil pack. It seems to idle a lot better and I'm getting normal readings on my O2 sensor in Bank 1 upstream location. We will see tomorrow how it does when I drive it more.

 

[mjonesjr84]

Can report that so far, knock on wood, I have not gotten the lean code again. The Jeep runs and drives great now. The 02 sensors read like they should be reading. I'm hoping that the coil pack was the final issue.

 

[209Wrangler]

reading posts, and have this same issue on my 2000 4.0. I replaced both o2 sensors, and still getting a lean bank 1 code after a month of light driving. I did not however know about the pcm reset procedure... Any instructions here would be appreciated...

Nic

 

[AndyA]

reading posts, and have this same issue on my 2000 4.0. I replaced both o2 sensors, and still getting a lean bank 1 code after a month of light driving. I did not however know about the pcm reset procedure... Any instructions here would be appreciated...

Nic

Disconnect positive cable from battery. Wait 10 minutes. Reconnect cable to battery. Andy

 

[209Wrangler]

thx brotha appreciate the quick response> if that doesn't help, im positive I bought a non NGK or mopar brand. ill switch them out

 

[mjonesjr84]

reading posts, and have this same issue on my 2000 4.0. I replaced both o2 sensors, and still getting a lean bank 1 code after a month of light driving. I did not however know about the pcm reset procedure... Any instructions here would be appreciated...

Nic

Check your front 3 spark plugs. You could have a bad coil pack not firing the plugs completely. The new coil pack fixed my P0171 Bank 1 lean code.

It is almost impossible to find a NTK or Mopar O2 sensor right now. I am running a mix of Walker and Denso without any issues.

 

[209Wrangler]

Check your front 3 spark plugs. You could have a bad coil pack not firing the plugs completely. The new coil pack fixed my P0171 Bank 1 lean code.

It is almost impossible to find a NTK or Mopar O2 sensor right now. I am running a mix of Walker and Denso without any issues.

I just replaced both sensors with walkers as well. I’ll check that coil pack too .

 

[JoeSpit]

my bank 1 #1 o2 sensor fluctuates voltage between .3 to 1.0 does that mean its bad? i just tripped the p0171 seemingly out of nowhere.