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Unread 07-07-2015, 03:32 PM   #1
CrystalC
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2005 KJ Liberty 
 
Join Date: Jul 2015
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System too lean

I am getting an error code system too lean Bank 2. does anyone know what this can indicate? I recently had a new fuel pump put in. Thanks

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Unread 07-07-2015, 06:06 PM   #2
megatone
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What is the code number?!!!
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Unread 07-07-2015, 08:32 PM   #3
tjkj2002
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Quote:
Originally Posted by megatone View Post
What is the code number?!!!
That would be P0174,any tech would know that.
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'02 Liberty sitting on 35" tires,HP44,RockJock60,and AtlasII t-case
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Unread 07-08-2015, 06:55 AM   #4
streetglideok
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Could be a variety of things. Misfires on bank 2, bad injectors, intake or exhaust leak on bank 2, etc. Would need to know how does bank 1 compare, and when is it lean, under load, at idle, all the time, etc. The code by itself won't give all that info.
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Unread 07-09-2015, 12:03 PM   #5
CrystalC
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Initially I was only getting bank 2 (p0174). Now it is coming up with both P0171 and P0174. No other codes present. The jeep drives smoothly but in the past 2 weeks has had 2 episodes where upon starting, it turns over but doesn't fire. This has been temporary and if I give it a couple of minutes it starts up fine. No issues while driving at all. I just had a new fuel pump put in and replaced the spark plugs. How would I know when it is too lean? Is this something the ODB II could tell me? Thanks
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Unread 07-10-2015, 12:30 AM   #6
megatone
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System too lean (or rich) codes come from the B1S1 and B2S1 sensors....a comprehensive OBD II scanner could inform you if the engine is running lean while under load, or at idle or all the time but you'll have to monitor real-time data of fuel trim values while the engine is running.

Maybe if you know how to interpret the voltage value of the B1S1 and B2S1 sensor data, you could get an idea of when its running lean, but the best and easiest way is looking at the fuel trim values because the sensors voltage readings are slightly affected by heat.....Lean=warmer......rich=cooler EGT's.

System too lean=unmetered air entering the engine=incoming air leak before cat upstream o2 sensors. Could be vacuum hoses, could be intake manifold gasket, could be faulty IAC......you did say it had trouble starting a couple times.....the IAC plays a big part in the initial start up of the engine, and if it is going bad or needs to be decarbonized, it could cause the Air to Fuel ratio to be too high resulting in a lean condition.


What was that obd code....again?
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Unread 07-10-2015, 06:10 PM   #7
streetglideok
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Check your fuel pressure. An IAC won't allow unmetered air in, so that won't cause a lean code. Either way, you need to know when it runs lean.
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Unread 07-10-2015, 06:55 PM   #8
megatone
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Quote:
Originally Posted by streetglideok View Post
Check your fuel pressure. An IAC won't allow unmetered air in, so that won't cause a lean code. Either way, you need to know when it runs lean.
Yup.....my mistake....shoulda said something like: An IAC that is stuck open will cause a lean code because the ecm is trimming fuel requirements based on what the IAC position should be when closed, even though the IAC may be stuck open a tad.
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Unread 07-11-2015, 06:49 AM   #9
streetglideok
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Quote:
Originally Posted by megatone View Post
Yup.....my mistake....shoulda said something like: An IAC that is stuck open will cause a lean code because the ecm is trimming fuel requirements based on what the IAC position should be when closed, even though the IAC may be stuck open a tad.
Where did you obtain this info? There is no IAC position sensor for it to know, it merely is working the IAC in response to desired RPMs. The MAP sensor will give the PCM the vacuum information. Surely BAR follows you guys better than that.
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Unread 07-11-2015, 02:55 PM   #10
megatone
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Quote:
Originally Posted by streetglideok View Post
Where did you obtain this info? There is no IAC position sensor for it to know, it merely is working the IAC in response to desired RPMs.
I obtained this information a few years ago at 10695 West Pierce Street in Avondale, Arizona......

I know there is no IAC position sensor......there is a spring loaded plunger that keeps the IAC closed when no voltage is flowing to it's solenoid which is inside the IAC body. If the solenoid is getting no electrical signal from the ECM the plunger should be closed....The ECM has no way of knowing whether the plunger is closed or not....all the ECM knows is that if it is not sending an electrical signal to the IAC then the IAC should be closed. But if it is stuck open a little it, it could cause emission problems.
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Unread 07-15-2015, 12:59 PM   #11
CrystalC
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Thanks for the input! I'm going to take it to a buddy that has the full scan
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Unread 07-16-2015, 12:21 AM   #12
CrystalC
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Just a quick note, I haven't had a chance to investigate the system too lean codes yet. The jeep didn't start again yesterday and this time someone was around. With someone under the hood, we managed to start it by him moving the throttle himself while I cranked the ignition and it fired up beautifully. I'm not sure what this means but I figure it's one more piece of the puzzle. Possibly not related to the lean codes. any thoughts?
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