O2 sensor and MAP sensor replacement

Tiny
KLHUDOCK64
  • MEMBER
  • 2004 JEEP LIBERTY
  • 3.7L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 152,000 MILES
My vehicle listed above Limited model is throwing two codes. One for an O2 sensor and one for a MAP sensor. I have both parts but I am thinking I should take care of the problem before I replace these parts. How hard is it to figure out if it's exhaust or manifold? Is this job fairly simple for a mechanic and would I be better off taking it to a professional?
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Thursday, March 4th, 2021 AT 1:56 AM

36 Replies

Tiny
MHPAUTOS
  • EXPERT
Hi there,

The first thing I would be doing is checking for a vacuum leak, both these codes can be set with with induction air leaks, the links below can help you diagnose this problem.
Mark (mhpautos)

https://www.2carpros.com/articles/how-to-test-an-oxygen-sensor-02-sensor
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
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Thursday, March 4th, 2021 AT 5:16 AM
Tiny
KLHUDOCK64
  • MEMBER
Thank you very much for your quick response and links.
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Thursday, March 4th, 2021 AT 5:43 AM
Tiny
MHPAUTOS
  • EXPERT
If you still have problems, don t hesitate to let me know so we can work through the problems.
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Thursday, March 4th, 2021 AT 5:48 AM
Tiny
MHPAUTOS
  • EXPERT
Have you had a chance to inspect things yet? Here is another link that will be of help:

https://www.2carpros.com/articles/how-to-replace-a-mass-air-flow-sensor-maf

Mark (mhautos)
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Saturday, March 6th, 2021 AT 2:10 AM
Tiny
KLHUDOCK64
  • MEMBER
Good Morning,

No, I have not yet checked it out. It's been pretty cold here. Starting Monday it will be between 50 and mid-60-degree weather. When I was younger the weather did not bother me. I look forward to a day when I can purchase a new vehicle. Buying used most of my life I know I'm going to inherit problems and the previous owners' ability to be honest is a big factor. As soon as I check it out I will let you know. I really appreciate this site. Thank you very much!
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Saturday, March 6th, 2021 AT 3:08 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I noticed it's been a couple of days since we heard from you. Have you made any progress? We are interested in knowing.

Take care and God Bless,

Joe
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Monday, March 8th, 2021 AT 7:21 PM
Tiny
KLHUDOCK64
  • MEMBER
Well, as I stated In throwing an O2 code and a MAP Sensor code. But I know until I get the exhaust leak fixed there's no point in really changing them. I plan on jacking it up tomorrow crawling under there and trying to see or feel where it's coming from and how major it is. Thanks for looking out.
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Monday, March 8th, 2021 AT 7:27 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
You are very welcome. Just a thought. If you have an exhaust leak prior to the catalytic converter, it can cause a lean fuel mixture because unmetered air can enter via the leak. Make sure to check around the exhaust manifold.

Let me know if I can help.

Joe
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Tuesday, March 9th, 2021 AT 4:43 PM
Tiny
KLHUDOCK64
  • MEMBER
I still didn't have time but I did want to say. The 02 sensor was bank 2 sensor two or down stream too rich. I'm not sure if I used the right terms I don't have my scan tool this moment (445am)l but wouldn't 2 and 2 mean below the converter? Not sure yet but I will let you know. I do know it seems to be flooding out and/or cutting out when I slow down while driving or coming to a stop. Plus every time I work on any vehicle one of several neighbors comes out and distracts me by striking up long conversations. It's very hard to get anything done without being rude. Thanks for your reply!
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Wednesday, March 10th, 2021 AT 1:58 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

If it is sensor 2, then you are correct. It will be after the converter. If it is running rich, check to make sure the fuel pressure is within spec. If it is, then we will need to check the coolant temp sensor as well as the injectors.

Here is a link that shows how fuel pressure it checked:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Also, here are the fuel pressure specs:

2004 Jeep Truck Liberty 4WD V6-3.7L VIN K
Pressure, Vacuum and Temperature
Vehicle Powertrain Management Fuel Delivery and Air Induction Fuel Pump Fuel Pressure Specifications Pressure, Vacuum and Temperature
PRESSURE, VACUUM AND TEMPERATURE
FUEL SYSTEM PRESSURE
If equipped with JTEC Powertrain Control Module using 3 electrical connectors: 339 kPa 34 kPa (49.2 psi 2 psi)
If equipped with NGC Powertrain Control Module using 4 electrical connectors: 400 kPa 34 kPa (58 psi 5 psi)

Let me know what you find or if you have other questions.

Take care,

Joe
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Wednesday, March 10th, 2021 AT 4:48 PM
Tiny
KLHUDOCK64
  • MEMBER
I was wrong. I had a lot going on the past week and was exhausted. So I crawled under this morning and low and be hold there is no catalytic converter. He ran flex pipe up to the front from where converter should have been and there is a leak towards manifold and there is one towards the back before or after the muffler. I do not think it has anything to do with the exhaust though. It has to be something else making it run too lean not rich as I had said at 4:45 am sorry about that. I know previous owner had replaced a manifold gasket and supposedly valve cover gaskets. It wants to stall out only after its warmed up after I've been driving for awhile. It starts right up in the morning with no problem. I'm thinking to start simple. Check air filter, spark plugs etc. I don't know. I got a quote for an exhaust front to back and it was over $1,000.00. $1,025.00 to be exact. The exhaust can wait. They didn't even want to consider a universal converter. I bought a $1,500.00 car because that's all I could afford at the time. If I had an extra $1,000.00 I would have bought a $2,500.00 car. I just do not know where to begin but you all have been very helpful. Until I figure it out I will have one foot on the brake and one on the gas when at a stop sign or red light. Thanks for everything.
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Wednesday, March 10th, 2021 AT 7:41 PM
Tiny
KLHUDOCK64
  • MEMBER
Codes I'm getting. P0108 Manifold Pressure Sensor Barametric Pressure Circuit High and P0158 02 Sensor Circuit High Voltage Bank 2 Sensor 2 if that helps. I wrote them down word for word. Thanks
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Wednesday, March 10th, 2021 AT 8:09 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

The idea that they are both high voltage codes could indicate a short. Have you checked the wiring and the connectors? There could be damage or a short. Also, disconnect the connectors and check for corrosion or a damaged pin in the connector or sensor.

Joe
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Thursday, March 11th, 2021 AT 1:57 PM
Tiny
KLHUDOCK64
  • MEMBER
Thank you so much. I was going to clean the MAP sensor so. I will definitely check that out. Also I noticed I can see that 02 Sensor and I don't think I'm supposed to be able to see it clear as day it looks like maybe someone just wired it in and clamped or attached it right there. Thanks to you guys I'm getting closer. Unfortunately it's dark here now. Tomorrow is another day. Ill try to remember to take a few pics. Also my muffler and tailpipe are fine. I inspected them. I'm thinking the leaks are either in the clamps or someplace on the flex pipe or closer to manifold I'll know more tomorrow. Have a great night.
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Thursday, March 11th, 2021 AT 3:17 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

You are very welcome. Let me know what you find or if you have other questions.

Take care and let me know what you find.

Joe
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Thursday, March 11th, 2021 AT 3:56 PM
Tiny
KLHUDOCK64
  • MEMBER
Well, I didn't get much done today but I did check the entire exhaust out. I'm pretty sure the O2 sensor is not supposed to be just hanging there and it's rough looking. Two pieces of flex pipe a few holes by the clamps. The rest of the old pipes going to muffler, the muffler itself and the tail pipe are fine. I have an O2 sensor I have a new MAP Sensor I'm going to get the left and right front pipes and a converter online for around $300 New. I am up loading a pic of that O2 sensor because I know its not supposed to look like that and out in the wide open like that I'm not sure but it doesn't look good to me. I checked the hose by map sensor for leaks. That sensor looks raggedy also. Ok I sure hope I'm on the right track. Maybe I can pay my brother to put that exhaust together once I get parts.
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Friday, March 12th, 2021 AT 3:17 PM
Tiny
KLHUDOCK64
  • MEMBER
I think I will just do it right and get Driver side Converter and passenger side and the Y pipe as long as muffler and tail pipe are good. NYS I need to pass emissions. This is inspected until the end of October but if it's going to get done I might as well do it right. And that O2 sensor has been hanging there in the rain and snow and wow I'm glad with your help I was able to find all this so it can get taken care of. Thanks again.
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Friday, March 12th, 2021 AT 5:35 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

The o2 sensor is bolted into the exhaust and will be exposed as in the pic. However, it looks like it may have been welded on the one side. If it is, that's going to be a problem because you won't be able to remove it.

Let me know.
Joe
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Friday, March 12th, 2021 AT 5:57 PM
Tiny
KLHUDOCK64
  • MEMBER
Wow, okay, thanks. Maybe it's a good idea to get the new exhaust parts then.
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Friday, March 12th, 2021 AT 7:16 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Honestly, I would recommend it. From what I can tell, someone used a generic type flex tubing to repair behind the sensor. It's really hard for me to tell simply because I'm not there.
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Friday, March 12th, 2021 AT 7:24 PM

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