2.4L 2002 15.5MPG replaced O2sensor still poor mpg

[jeepykj]

Hi, I have a 2002 2.4L KJ (UK). its very poor on mpg currently only getting around 15.5mpg around town. The second downstream oxygen sensor showed a fault of no signal voltage from the downstream O2 sensor, and good signal voltage from first O2 sensor when looking at OBD software.

so replaced the downstream O2 with a new Crown o2 sensor p/n 56041846AA. [which was the third sensor I tried as previous ones didnt have quite the same electrical plug guides so could not fit]

After I fitted the new sensor I reset the mpg counter and went for a drive, and after a bit of a drive the read out had eventually climbed to 19.1mpg. so it seemed the problem fixed.

However a few more trips daily driving the mpg has averaged around 15.7 at its highest. so while I havent had chance to connect the OBD software thing to the vehicle, Im pretty sure its not fixed the problem

so any ideas on this ? is there a heater circuit fuse that feeds this O2 sensor that perhaps is blown that I can check ?

many thanks
Jon

 

[HoosierJeeper]

Get an NTK or Mopar sensor and report back. Crown just reboxes stuff so no idea who actually made the sensor.

 

[Jeremy-WI]

You should replace the O2 sensor closest to the engine bank 1, sensor 1 as that is the one that affects mileage, also check intake air temp sensor and coolant temp sensor

 

[jeepykj]

Get an NTK or Mopar sensor and report back. Crown just reboxes stuff so no idea who actually made the sensor.

I had replaced with NTK sensor first of all, but it came with newer black electrical socket, so I cut off the old socket and wired it back on keeping sure to the same colour wires married up. , that sensor didnt have any effect , still produced no signal voltage (OBD software has sensor graph which was flat line, where as sensor 1 working fine producing signal voltage) so I assumed the NTK sensor was wrong type. so this weekend got a new crown sensor that has correct plug type (light brown plastic housing) and fitted it on sunday. after a test drive on sunday getting a 19mpg read out I thought the problem was fixed.

 

[towpro]

May I join this thread? I also have piss poor MPG but thought it was normal.
driving back roads, 35mph, maybe a stop sign every mile or so, I was getting around 11-12.
After new tires and alignment I see maybe 13-14. I am not driving fast, or ******* Acceleration either (not a kid).
but at 70mph, flat land, cruise set, I see 19. even at 65mph cruise I have not been able to see 20 on the overhead console. In fact I think as I slow down the MPG gets worse

But I am willing to try this.

First, how many O2 sensors are there, and where is "bank 1, sensor 1" physically located on my 06?
thanks!

 

[JasonJ]

May I join this thread? I also have piss poor MPG but thought it was normal.
driving back roads, 35mph, maybe a stop sign every mile or so, I was getting around 11-12.
After new tires and alignment I see maybe 13-14. I am not driving fast, or ******* Acceleration either (not a kid).
but at 70mph, flat land, cruise set, I see 19. even at 65mph cruise I have not been able to see 20 on the overhead console. In fact I think as I slow down the MPG gets worse

But I am willing to try this.

First, how many O2 sensors are there, and where is "bank 1, sensor 1" physically located on my 06?
thanks!

Number of sensors depends on which engine is installed. Jeepy has a 2.4, so two. There are 4 on the 3.7l equipped KJ's.

 

[tjkj2002]

I had replaced with NTK sensor first of all, but it came with newer black electrical socket, so I cut off the old socket and wired it back on keeping sure to the same colour wires married up. , that sensor didnt have any effect , still produced no signal voltage (OBD software has sensor graph which was flat line, where as sensor 1 working fine producing signal voltage) so I assumed the NTK sensor was wrong type. so this weekend got a new crown sensor that has correct plug type (light brown plastic housing) and fitted it on sunday. after a test drive on sunday getting a 19mpg read out I thought the problem was fixed.

You need to buy the O2 from the dealership using the VIN over there otherwise it's a total crap shoot if your going to get the correct part.

2nd we need more info..........

Mileage on vehicle,what services have been done,temp(ambient),stop and go or highway,fuel grade using,and what was the mileage before the code set?

There are so many factors that can effect mpg's and the big one right now is the weather and gas grade,it's going to go down(mpg's) at this time of year no matter what.

May I join this thread? I also have piss poor MPG but thought it was normal.
driving back roads, 35mph, maybe a stop sign every mile or so, I was getting around 11-12.
After new tires and alignment I see maybe 13-14. I am not driving fast, or ******* Acceleration either (not a kid).
but at 70mph, flat land, cruise set, I see 19. even at 65mph cruise I have not been able to see 20 on the overhead console. In fact I think as I slow down the MPG gets worse

But I am willing to try this.

First, how many O2 sensors are there, and where is "bank 1, sensor 1" physically located on my 06?
thanks!

Don't even pay attention to that overhead console,99.999999999% of the time it's not even close to being correct.

Plus 65-70mph is not the optimal cruise speed for a KJ and good mpg's(3.7 with auto trans),75-80 is the best speed.Getting on it every once in a while actually helps improve mpg's.

And again without maintenance history 19mpg's is pretty good for a KJ.

 

[tommudd]

The 3.7s do not like to be lugged down at all.
They are more of a run it like you stole it type of 4X4.
All of my KJs gets ran down the highway at 75 plus, entering the highway no feathering the throttle stomp and go. Pulling out on to the main road in the mornings or going anywhere , hits the rev limiter almost everytime
Run it good, keep up on maintenance, all fluids, changing plugs at least every 30,000 with the right plugs , air filter replaced on regular schedule all comes in to play. Plus if larger tires, the right gearing .

On the 04 with 32s/4 inches of lift and heavy bumpers/skids etc I got over 233 MPG going across Pennsylvania .
Anyone who's crossed that state knows its all up and down and down and up! LOL

 

[HoosierJeeper]

The 3.7s do not like to be lugged down at all.
They are more of a run it like you stole it type of 4X4.
All of my KJs gets ran down the highway at 75 plus, entering the highway no feathering the throttle stomp and go. Pulling out on to the main road in the mornings or going anywhere , hits the rev limiter almost everytime
Run it good, keep up on maintenance, all fluids, changing plugs at least every 30,000 with the right plugs , air filter replaced on regular schedule all comes in to play. Plus if larger tires, the right gearing .

On the 04 with 32s/4 inches of lift and heavy bumpers/skids etc I got over 233 MPG going across Pennsylvania .
Anyone who's crossed that state knows its all up and down and down and up! LOL

Yep, I stopped babying it and get at least 1-2 better MPG across all conditions. I don't think I go as hard as Tom :gr_grin: but I'm not afraid to bury my foot into the KJ.

 

[jtgasparich]

Recently got my first new (to me) Jeep! An '02 Liberty 3.7 with 187k km on it.

The check engine light is on, so I got the shop to pull some codes for me. Here's what came up:

P 0161- HO2S Heater Circuit bank 2 sensor 2
P 0158- HO2S Circuit High Voltage Bank 2 sensor 2

So, do I need to replace an O2 sensor? And which one do these codes refer to?

Thanks in advance!

 

[ltd02]

Recently got my first new (to me) Jeep! An '02 Liberty 3.7 with 187k km on it.

The check engine light is on, so I got the shop to pull some codes for me. Here's what came up:

P 0161- HO2S Heater Circuit bank 2 sensor 2
P 0158- HO2S Circuit High Voltage Bank 2 sensor 2

So, do I need to replace an O2 sensor? And which one do these codes refer to?

Thanks in advance!

I'd check the wiring too to make sure its ok but replacement would be the likely solution. This would be the downstream right side (passenger side in the US) after the catalytic converter. Probably the easiest to change. Use the NTK brand only.