Code P0171

[Kristehansen]

So I bought my Jeep ten plus years ago and when things go wrong it’s typically because they haven’t been changed since I bought it. I do the regular maintain every other week but when things go exceptionally wrong more times then not, it just hasn’t been changed in ten years.
My Jeep started to sputter and not accelerate right causing the engine light to go on. Discovered it was the p0171 code and thought it would be an easy fix to just go ahead and change out the fuel pump. Started it up and it ran super smooth so thought it was fixed. Went to work and it was doing the same thing. So I started reading up on the forums and said to get a O2 sensor upstream (I got the good one, not mopar or Bosch) and that should fix the issue. Is this correct or so I start needing to save money and just replace it all?

 

[CharlesHS]

Typically the code will be triggered by a lean condition in the engine. ... Misfire– If the air fuel mixture has gotten too far from factory specs, this can cause the Wrangler to misfire.
The O2 sensor sends voltage signals to the ECU which controls the pulse duration of the fuel injectors.
IF the up stream O2 sensors have been in more than 125K miles; there is a good chance the could need replacing.

NGK 23138 (upstream) and 23141 (downstream) for your 2002 2.5L

Here is some good reading from the Forum on O2 sensors.

https://wranglertjforum.com/threads/the-official-jeep-wrangler-tj-oxygen-o2-sensor-thread.4068/

 

[ColoJeep]

You might take a peak at the MAP sensor and vacuum lines also.

 

[Kristehansen]

Typically the code will be triggered by a lean condition in the engine. ... Misfire– If the air fuel mixture has gotten too far from factory specs, this can cause the Wrangler to misfire.
The O2 sensor sends voltage signals to the ECU which controls the pulse duration of the fuel injectors.
IF the up stream O2 sensors have been in more than 125K miles; there is a good chance the could need replacing.

NGK 23138 (upstream) and 23141 (downstream) for your 2002 2.5L

Here is some good reading from the Forum on O2 sensors.

https://wranglertjforum.com/threads/the-official-jeep-wrangler-tj-oxygen-o2-sensor-thread.4068/

Like I said earlier, sadly when things like this happens with the Jeep.. it’s things that haven’t been replaced for 10+years I ordered a new O2 upstream sensor and my next thing while I have the hood up is to look at everything you mentioned and more. Thank you for the information!

 

[Boinked]

Test don't guess. Most of us (including me) will load a parts cannon and toss hundreds of dollars worth of parts at a problem and may or may not fix it.

My advice is to do some research on what triggers the PCM/ECM to set the code. Then look at how you can test each thing to prove that is your problem before you spend good money on a good part.

 

[Kristehansen]

Test don't guess. Most of us (including me) will load a parts cannon and toss hundreds of dollars worth of parts at a problem and may or may not fix it.

My advice is to do some research on what triggers the PCM/ECM to set the code. Then look at how you can test each thing to prove that is your problem before you spend good money on a good part.

Well I would do all of this absolutely but my whole family just moved to Oklahoma from Oregon so my dads welding/mechanic shop is non existent at the moment. So we’re trying to do the things we can before I take it to an auto shop to diagnose the problem. I won’t put anymore money into my beloved Jeep after I get this O2 sensor. It’s just a “might as well” thing for me because it hasn’t been done for a really long time:/

 

[CharlesHS]

IF you have access to a Scan Tool that does Live Data you can read the voltages for the O2 sensors.
O2 sensor voltages can be .1 VDC to .9 VDC; you should see the voltage vary between .7 and .4 VDC.
.9 being RICH and .1 being LEAN.

 

[Kristehansen]

IF you have access to a Scan Tool that does Live Data you can read the voltages for the O2 sensors.
O2 sensor voltages can be .1 VDC to .9 VDC; you should see the voltage vary between .7 and .4 VDC.
.9 being RICH and .1 being LEAN.

Unfortunately I don’t have access to this. :/

 

[Kristehansen]

Update. Replaced the O2 sensor, put in a new vacuum valve and my dad noticed my exhaust was loose. And needless to say, everything works! The picture is a over due need of replacing O2 sensor! Yikes!