Symptoms: Rough idle after hot start, P0431 codes, CEL illuminated.
2005 Jeep Wrangler Rubicon
4.0L I6 6 speed manual
82k miles
I had a suspicion my catalytic converters might be failing. My engine seems to run a little warm, I have heat soak issues, and mild hesitation in mid range rpm, with low power above 3k. CEL is on with P0431 code set, and resets every drive cycle. I have a childhood friend who runs a family exhaust shop (second generation family business) but he was too busy to look at it today, and was quoting $850 to replace the 3 cats, and reuse my O2 sensors. Seemed a little high, more on that later. He would have back pressure tested it, I am sure. But I wanted to know what the deal is myself, so I dove in on my own.
I would advise you disconnect your battery, to reset any codes, and to prevent it from running down due to the hood being open (underhood light). Also to prevent any accidental shorts, like touching a socket wrench to the starter post and scaring the shit out of yourself when it rains sparks and the jeep tried to start itself while in gear when you are laying under it. Not that anything like this has even happened to me, more than once.
Step 1. Disconnect all O2 sensor harnesses by pushing down on the release clip and pulling out. The bank 2 downstream was a bitch. Its tucked up above the bellhousing. I had to lay on top of the engine and reach it from above.
Step 2. Use a penetrating spray of your choice on the bolts and the O2 sensor and let it sit and soak in for a while.
Step 3. Place a jack stand under the exhaust to hold it up while removing the flange bolts.
Step 4. Using a 15mm short socket on the end of a wobble extension (or a u joint if you have one) remove the four flange bolts. Two per exhaust collector.You might need multiple extensions to get to the bolts. Be sure the socket is securely engaged. You do not want to round these off, unless you just really want to pull the exhaust manifold too. Totally up to you here.
Step 5. Remove 4x 14mm nuts from transmission mount below the skid plate.
Step 6. Place a jack under the skid plate and lift it up slightly.
Step 7. Place a jack stand under the transmission to support it when the skid plate is removed. Be sure it is securely positioned to take the weight, and not damage the transmission.
Step 8. Remove all 6 bolts holding the skid plate to the frame and lower the skid plate using the jack. Set the jack and skid plate aside. (If you have a Rubicon like me, you will also need to remove and secure the locker pump bracket, its 4 14mm bolts accessed from above the skid plate at the rear. Be sure to support the bracket and pumps with a zip tie or mechanics wire so they don't dangle and damage the wires or hoses.)
Step 9. Use a penetrating spray of your choice on the exhaust flange nuts where the third catalyst meets the muffler pipe. Let is soak a while.
Step 10. Using a 15mm socket remove the two flange nuts. You might need to beat the socket on for better engagement. Just know, you are also going to have to beat it off (don't laugh you perverts). Screw it back on a few turns and wiggle the socket off.
Step 11. Pull the entire exhaust assembly from the third catalyst forward until the hanger is clear of the transmission mount.
Step 12. You should now be able to remove the assembly,
You can now remove the O2 sensors in manifold with a 22mm wrench if you are replacing them as well.
Findings:
One of these things is NOT like the other.
The bank 1 (forward catalyst) is intact, and clear of obstructions. Looks serviceable.
The bank 2 (rearward catalyst) is hollow. The ceramic material is trapped in the exhaust pipe creating a restriction, and causing the O2 sensor to set the CEL for P0431. Bank 2 is fucked. Sorry for the bad picture, hard to light it up, and snap it at the same time with my phone that has the focus of 10 year old kid with A.D.D. on a Redbull binge.
Results:
Ordered this cat set for $266 on Amazon:
https://www.amazon.com/gp/product/B0031G6YT6/?tag=wranglerorg-20
Ordered these NTK O2 sensors (all 4 of them) on Rock Auto for under $100 shipped:
So I am $366-ish into a job that was quoted to me at $850 not including the O2 sensors. You can do this job yourself, probably. I am all for supporting small business, but that's a steep markup on an easy job. I had the exhaust out in 35 mins. I had trouble with one sensor, but was able to get it out. The other three came out easily.
All in I had about an hour in this job, and expect going back, maybe 1.5 hours. 2.5 hours total labor.
Now we wait on parts to show up and reverse the steps above.
Stayed tuned next week for another addition of Fixing Shit That Doesn't Work Right On My Jeep!
2005 Jeep Wrangler Rubicon
4.0L I6 6 speed manual
82k miles
I had a suspicion my catalytic converters might be failing. My engine seems to run a little warm, I have heat soak issues, and mild hesitation in mid range rpm, with low power above 3k. CEL is on with P0431 code set, and resets every drive cycle. I have a childhood friend who runs a family exhaust shop (second generation family business) but he was too busy to look at it today, and was quoting $850 to replace the 3 cats, and reuse my O2 sensors. Seemed a little high, more on that later. He would have back pressure tested it, I am sure. But I wanted to know what the deal is myself, so I dove in on my own.
I would advise you disconnect your battery, to reset any codes, and to prevent it from running down due to the hood being open (underhood light). Also to prevent any accidental shorts, like touching a socket wrench to the starter post and scaring the shit out of yourself when it rains sparks and the jeep tried to start itself while in gear when you are laying under it. Not that anything like this has even happened to me, more than once.
Step 1. Disconnect all O2 sensor harnesses by pushing down on the release clip and pulling out. The bank 2 downstream was a bitch. Its tucked up above the bellhousing. I had to lay on top of the engine and reach it from above.
Step 2. Use a penetrating spray of your choice on the bolts and the O2 sensor and let it sit and soak in for a while.
Step 3. Place a jack stand under the exhaust to hold it up while removing the flange bolts.
Step 4. Using a 15mm short socket on the end of a wobble extension (or a u joint if you have one) remove the four flange bolts. Two per exhaust collector.You might need multiple extensions to get to the bolts. Be sure the socket is securely engaged. You do not want to round these off, unless you just really want to pull the exhaust manifold too. Totally up to you here.
Step 5. Remove 4x 14mm nuts from transmission mount below the skid plate.
Step 6. Place a jack under the skid plate and lift it up slightly.
Step 7. Place a jack stand under the transmission to support it when the skid plate is removed. Be sure it is securely positioned to take the weight, and not damage the transmission.
Step 8. Remove all 6 bolts holding the skid plate to the frame and lower the skid plate using the jack. Set the jack and skid plate aside. (If you have a Rubicon like me, you will also need to remove and secure the locker pump bracket, its 4 14mm bolts accessed from above the skid plate at the rear. Be sure to support the bracket and pumps with a zip tie or mechanics wire so they don't dangle and damage the wires or hoses.)
Step 9. Use a penetrating spray of your choice on the exhaust flange nuts where the third catalyst meets the muffler pipe. Let is soak a while.
Step 10. Using a 15mm socket remove the two flange nuts. You might need to beat the socket on for better engagement. Just know, you are also going to have to beat it off (don't laugh you perverts). Screw it back on a few turns and wiggle the socket off.
Step 11. Pull the entire exhaust assembly from the third catalyst forward until the hanger is clear of the transmission mount.
Step 12. You should now be able to remove the assembly,
You can now remove the O2 sensors in manifold with a 22mm wrench if you are replacing them as well.
Findings:
One of these things is NOT like the other.
The bank 1 (forward catalyst) is intact, and clear of obstructions. Looks serviceable.
The bank 2 (rearward catalyst) is hollow. The ceramic material is trapped in the exhaust pipe creating a restriction, and causing the O2 sensor to set the CEL for P0431. Bank 2 is fucked. Sorry for the bad picture, hard to light it up, and snap it at the same time with my phone that has the focus of 10 year old kid with A.D.D. on a Redbull binge.
Results:
Ordered this cat set for $266 on Amazon:
https://www.amazon.com/gp/product/B0031G6YT6/?tag=wranglerorg-20
Ordered these NTK O2 sensors (all 4 of them) on Rock Auto for under $100 shipped:
So I am $366-ish into a job that was quoted to me at $850 not including the O2 sensors. You can do this job yourself, probably. I am all for supporting small business, but that's a steep markup on an easy job. I had the exhaust out in 35 mins. I had trouble with one sensor, but was able to get it out. The other three came out easily.
All in I had about an hour in this job, and expect going back, maybe 1.5 hours. 2.5 hours total labor.
Now we wait on parts to show up and reverse the steps above.
Stayed tuned next week for another addition of Fixing Shit That Doesn't Work Right On My Jeep!
Last edited:
you need 4 3/8 thick washers and a set of gear wrenches made the install a lot easier. also use some high temp copper anti seize on the threads especially on your 02 sensors . I was lucky whoever put mine in before I got it used it and all 4 sensors came right out with a wrench (no cussing needed) 
