P0161 Check Engine Light

WolfGT

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#1
On my way to the stone yard this morning my check engine light came on. No noticeable problems. After loading the trailer with stone and starting the Jeep back up I had the normal hot restart stumbles. Which has been getting worse lately even though I have implemented every heat option there is for the fuel rail (maybe this problem is related to the code). Ran fine on the way home. Got home and hooked up the scanner.

P0161: O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)

I figured before I attempted to troubleshoot the issue I would post on here and see if this is any type of common issue on the TJ. And maybe get some pointers on where to start.
 

LBarr2002

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#2
Just need to replace bank 2 sensor 2, which I think is the back 3 cylinder downstream sensor. That shouldn't have changed your heat soak hot start issues. I wonder if that is old fuel (if you don't drive it much) or an increase in ethanol content of the fuel you're getting.
 
#3
On my way to the stone yard this morning my check engine light came on. No noticeable problems. After loading the trailer with stone and starting the Jeep back up I had the normal hot restart stumbles. Which has been getting worse lately even though I have implemented every heat option there is for the fuel rail (maybe this problem is related to the code). Ran fine on the way home. Got home and hooked up the scanner.

P0161: O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)

I figured before I attempted to troubleshoot the issue I would post on here and see if this is any type of common issue on the TJ. And maybe get some pointers on where to start.
Have you tried running ethanol free gas?
 

WolfGT

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#4
Jeep fixed. Replaced the O2 sensor. Here is the part.

o2sensor.jpg

It was pretty easy. That specific sensor was easily accessible from under the vehicle. Cleared the code and went for a drive to see if the code came back. No code. Then used the Jeep to go get a load of concrete block. Still no code. Good to go. Still doing the spit & sputter game on hot start. I'll hunt down a zero ethanol station and try that next. Pretty sure I saw one down the road.

During research I noticed that the 4.0 comes in two configurations and mine is considered the "California emissions" version with 4 O2 sensors. The "Federal emissions" version just has 2 sensors. Just wondering, is the California version common around here or did I somehow stumble into it?
 

LBarr2002

LIFETIME
SUPPORTER
#5
Jeep fixed. Replaced the O2 sensor. Here is the part.

View attachment 22918

It was pretty easy. That specific sensor was easily accessible from under the vehicle. Cleared the code and went for a drive to see if the code came back. No code. Then used the Jeep to go get a load of concrete block. Still no code. Good to go. Still doing the spit & sputter game on hot start. I'll hunt down a zero ethanol station and try that next. Pretty sure I saw one down the road.

During research I noticed that the 4.0 comes in two configurations and mine is considered the "California emissions" version with 4 O2 sensors. The "Federal emissions" version just has 2 sensors. Just wondering, is the California version common around here or did I somehow stumble into it?
What year is yours? I think all the later ones had 4. My LJ did.
 
#7
there is usually 1 before the cat and 1 after the cat and since your year uses a split manifold design(2 manifolds,2 cats= 4 sensors) I think thats why theres 4. Should be the same for any of the TJs with the 2 small Cats. My 97 only has1 Cat and has 2 o2 Sensors.
 
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