I had a CEL with a P2098: Post Catalyst Fuel Trim System Too Lean Bank 2 code recently. Since I suspect my O2 sensors are more than 15 years old, I figured swapping them would be the first fix I'd try.
This walk-through is for the 4.0L I6 with California emissions. The 4.0L engine with Federal emissions and the 2.4L engine only have two O2 sensors in different locations than my engine, but the general process is the same.
Step 1: Get the tools and parts.
You want an O2 sensor socket and a tap to chase the threads. I used these tools, but there are other options just like them:
https://www.amazon.com/gp/product/B00GMN4D1Q/?tag=wranglerorg-20
https://www.amazon.com/gp/product/B000XETMW0/?tag=wranglerorg-20
You might as well do all the sensors at once. The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread has all the right part numbers for the NGK/NTK sensors you need.
Step 2; Find all the O2 sensors and plugs.
The FSM diagrams are only so good and they don't show where the plugs are. Fortunately, the wiring harnesses are short. Unfortunately, one of the plugs is hard to get to. Here's where the O2 sensors are:
The 1/1 and 2/1 plugs are on the plastic rail that runs along the intake manifold, with 1/1 at the front and 2/1 at the rear.
The 1/2 plug is below the driver's side motor mount. And the 2/2 plug is mounted right on top of the forward end of the transmission — which makes it really hard to reach.
Step 3: Remove an old O2 sensor.
I was fortunate that the old sensors weren't too stuck, but soaking them with penetrating oil beforehand can help.
Unhooking the plugs takes two hands, one to release the catch and another to pull the plug apart. The only plug that's tricky is the 2/2 plug on top of the transmission. If you get right under the Jeep, you can snake one hand up next to the Bank 2 cat to release the catch and get another hand up over the transmission to pull the plug.
I'm using a glove in this picture, but I recommend doing this with bare hands so you can tell what you're working with.
Step 4: Chase the threads.
It's easier to do this with a box end wrench so you can work the tool back and forth without having the wrench slip off.
Step 5: Install a new O2 sensor.
Make sure you have the right O2 sensor for the position it's being installed in. The plugs are keyed, so you can compare the old and new plugs. Also check to make sure the harness is the right length.
The instructions in the NGK/NTK box say to hand tighten then add 1/2 turn with the wrench. FSM says tighten to 22 ft. lbs., which is probably about the same.
I know some people suggest adding anti-seize to the O2 sensor threads, but both the FSM and NGK/NTK instructions advise against this. The O2 sensors should already have anti-seize already on them from the factory.
Step 6: Plug the O2 sensor in.
If you put a sensor in the wrong place, the keyed plug won't go in. Otherwise the plug just snaps into place.
Finish: Make sure everything works.
If you haven't done so already, clear any remaining fault codes from the PCM so the CEL goes off. If you have an OBD-II reader and app, plug it in and pull up the O2 sensor diagnostics. Start up the engine and check to make sure that the CEL stays off and there are no new faults. Watch the O2 sensor readings while the engine idles until the sensors warm up and start providing good data. The reported O2 sensor voltage should range between 0 and 1 Volts.
This walk-through is for the 4.0L I6 with California emissions. The 4.0L engine with Federal emissions and the 2.4L engine only have two O2 sensors in different locations than my engine, but the general process is the same.
Step 1: Get the tools and parts.
You want an O2 sensor socket and a tap to chase the threads. I used these tools, but there are other options just like them:
https://www.amazon.com/gp/product/B00GMN4D1Q/?tag=wranglerorg-20
https://www.amazon.com/gp/product/B000XETMW0/?tag=wranglerorg-20
You might as well do all the sensors at once. The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread has all the right part numbers for the NGK/NTK sensors you need.
Step 2; Find all the O2 sensors and plugs.
The FSM diagrams are only so good and they don't show where the plugs are. Fortunately, the wiring harnesses are short. Unfortunately, one of the plugs is hard to get to. Here's where the O2 sensors are:
The 1/1 and 2/1 plugs are on the plastic rail that runs along the intake manifold, with 1/1 at the front and 2/1 at the rear.
The 1/2 plug is below the driver's side motor mount. And the 2/2 plug is mounted right on top of the forward end of the transmission — which makes it really hard to reach.
Step 3: Remove an old O2 sensor.
I was fortunate that the old sensors weren't too stuck, but soaking them with penetrating oil beforehand can help.
Unhooking the plugs takes two hands, one to release the catch and another to pull the plug apart. The only plug that's tricky is the 2/2 plug on top of the transmission. If you get right under the Jeep, you can snake one hand up next to the Bank 2 cat to release the catch and get another hand up over the transmission to pull the plug.
I'm using a glove in this picture, but I recommend doing this with bare hands so you can tell what you're working with.
Step 4: Chase the threads.
It's easier to do this with a box end wrench so you can work the tool back and forth without having the wrench slip off.
Step 5: Install a new O2 sensor.
Make sure you have the right O2 sensor for the position it's being installed in. The plugs are keyed, so you can compare the old and new plugs. Also check to make sure the harness is the right length.
The instructions in the NGK/NTK box say to hand tighten then add 1/2 turn with the wrench. FSM says tighten to 22 ft. lbs., which is probably about the same.
I know some people suggest adding anti-seize to the O2 sensor threads, but both the FSM and NGK/NTK instructions advise against this. The O2 sensors should already have anti-seize already on them from the factory.
Step 6: Plug the O2 sensor in.
If you put a sensor in the wrong place, the keyed plug won't go in. Otherwise the plug just snaps into place.
Finish: Make sure everything works.
If you haven't done so already, clear any remaining fault codes from the PCM so the CEL goes off. If you have an OBD-II reader and app, plug it in and pull up the O2 sensor diagnostics. Start up the engine and check to make sure that the CEL stays off and there are no new faults. Watch the O2 sensor readings while the engine idles until the sensors warm up and start providing good data. The reported O2 sensor voltage should range between 0 and 1 Volts.