Folks, After replacing all the O2 sensors, I am still getting 4 alert codes indicating High Control. The resistance for each sensor is good. It looks like the problem could be in the ECU. I'm wondering if anyone agrees and if so what should I do. Can I send the ECU out to be evaluated/rebuilt or just purchase a replacement. Any suggestions on whom I can contact to evaluate it or whom I can purchase a replacement. TJ
Still getting codes after replacing O2 sensors
- Thread starter Tom Jensen
- Start date
What brand of O2 sensors did you use?
@Wranglerfix is the only person you should trust for PCM / ECU repair and replacement.
wranglerfix.com
Also, there is no such thing as an HO2 sensor on your TJ. It's not measuring water, it's measuring oxygen.
@Wranglerfix is the only person you should trust for PCM / ECU repair and replacement.
wranglerfix.com
Also, there is no such thing as an HO2 sensor on your TJ. It's not measuring water, it's measuring oxygen.
Those would be H2O sensors
chemistry was an important subject in school.I think the OP is just referring to Heated Oxygen(O2) Sensors.
But seriously, call up WranglerFix for some assistance with the ECM.
Those would be H2O sensors
I think the OP is just referring to Heated Oxygen(O2) Sensors.
But seriously, call up WranglerFix for some assistance with the ECM.
That's right, I read it wrong.
First time I've ever heard someone refer to them as HO2 sensors, haha!
What were your original codes?
The sensors' job is to tell you there is a problem. It doesn't always mean they're bad.
Regarding O2 Sensors, I have an '06 TJ Rubicon, 6 cyl, 4.0. I had trouble getting the codes to clear after having changed the offending sensor (in this case, 2nd bank upstream). I tried two different O2 sensors (NTK brand), etc., so I figured there was a different problem.
One of the posts here suggested the pre-catalyst was a problem. I was not looking forward to tackling that, but finally ordered the part and got to it. I needed an emissions inspection before getting the tags renewed, so I didn’t have much choice.
This post will hopefully help out Tom Jensen, even though it's an old post. But also, hopefully it will be helpful to others.
I purchased a Flowmaster (2049170 Flowmaster Catalytic Converter) from Amazon. Use the Amazon link here on the forum, it helps the forum.
I pulled off the old one by removing the 4 bolts (two per pipe) coming off of the exhaust manifold. Look at some YouTube vids for that, it's a bit tricky, but videos are helpful. Also, I did most of the work from under the Jeep but needed extensions to the ratchet. Spray the bolts a day or two ahead of time with PB or WD-40, and spray them a couple times over a couple days leading up to your repair weekend. It helps when those lubricants have time to work.
The OEM pre-cat to catalyst, to muffler pipe is a single unit, so it can be awkward and heavy to remove. The two bolts to the muffler were solid rust, and I couldn't remove them. I finally cut the pipe in front of the muffler with a grinder. I wish I had a sawsall, it would have been easier. Be careful on this step.
Once removed, I looked into the opening to the pre-cat. Photo 1 attached. To my surprise, only one pipe had the catalyst reticulate material inside. The second bank catalyst was completely empty. This attests to the O2 and computer not being able to triangulate sensor readings. Clearly, the pre-cat was the issue.
Having removed the entire unit, I was curious where all the catalyst reticulate material went. I decided for giggles, to cut the pipe just in front of the catalytic converter and found the decimated material. This had the secondary consequence of clogging the catalytic converter (Photo 2). Not only was there a pile of reticulate mulch in there, but it had also plugged some of the catalytic converter reticulate as well. This would figure into the loss of performance and worse than usual bad gas mileage.
The extent of debris is shown in the third photo.
While I'm at it, here are some other helpful bits:
The Flowmaster kit did not come with flange bolts or the clip nuts. In looking at the old bolts, it was clear they needed to be replaced. I purchased a full set of replacement parts, OEM. I had trouble finding them and found some on eBay. That said, they took two weeks to deliver, charged for shipping for each bolt ($8 per bolt), even though they all came in one sealed package from a Chrysler dealer in California. A tip here is to look at the dealers' parts counters before you go on eBay. I could have saved time and money. This waiting also goofed up my weekend plans. Try to get all the parts you need before beginning work (duh).
Putting the Flowmaster unit back on was not as difficult, but still tricky. The new pipe came in two sections, so it wasn't as heavy, lifting it into place. I bungeed it into place so I didn’t have to lift it while putting in the bolts. Then mated to the exhaust manifold, in a rough-fit fashion so I could align it for the bolts. Although aligning the flanges and seating the pipe to the exhaust manifold took some finesse. I got the flanges mostly aligned and loose-fit the bolts. I tightened the bolts, back and forth, one turn for each bolt to evenly seat the flanges. But you have to get out from under, look from under the hood to see if they're even (Photo 4). Or have a spotter to guide you from up top. I tested it after getting everything bolted in by running the engine and saw some exhaust leaking from the mated flanges. Clearly, I didn’t get them aligned right. So, I loosened all four, and went slowly back at it, getting up and checking up top for good seating.
You can over-tighten and bend the Flowmaster flanges. Be careful and observe the torque requirements.
In between all of that, I was able to get the catalytic converter pipe connected to the twin pre-cat pipe. The U-bolt that connects those two pipes is not as good as other types. Your results may vary, but I had a leak. From the muffler flange, I was able to remove the old cut piece of pipe, and mate the catalytic converter pipe to the muffler. I should have replaced the muffler while I was at it. But honestly, the muffler is much easier to replace and I can do that separately.
The codes cleared, and it drives soooo muuchhhh bettter.
One of the posts here suggested the pre-catalyst was a problem. I was not looking forward to tackling that, but finally ordered the part and got to it. I needed an emissions inspection before getting the tags renewed, so I didn’t have much choice.
This post will hopefully help out Tom Jensen, even though it's an old post. But also, hopefully it will be helpful to others.
I purchased a Flowmaster (2049170 Flowmaster Catalytic Converter) from Amazon. Use the Amazon link here on the forum, it helps the forum.
I pulled off the old one by removing the 4 bolts (two per pipe) coming off of the exhaust manifold. Look at some YouTube vids for that, it's a bit tricky, but videos are helpful. Also, I did most of the work from under the Jeep but needed extensions to the ratchet. Spray the bolts a day or two ahead of time with PB or WD-40, and spray them a couple times over a couple days leading up to your repair weekend. It helps when those lubricants have time to work.
The OEM pre-cat to catalyst, to muffler pipe is a single unit, so it can be awkward and heavy to remove. The two bolts to the muffler were solid rust, and I couldn't remove them. I finally cut the pipe in front of the muffler with a grinder. I wish I had a sawsall, it would have been easier. Be careful on this step.
Once removed, I looked into the opening to the pre-cat. Photo 1 attached. To my surprise, only one pipe had the catalyst reticulate material inside. The second bank catalyst was completely empty. This attests to the O2 and computer not being able to triangulate sensor readings. Clearly, the pre-cat was the issue.
Having removed the entire unit, I was curious where all the catalyst reticulate material went. I decided for giggles, to cut the pipe just in front of the catalytic converter and found the decimated material. This had the secondary consequence of clogging the catalytic converter (Photo 2). Not only was there a pile of reticulate mulch in there, but it had also plugged some of the catalytic converter reticulate as well. This would figure into the loss of performance and worse than usual bad gas mileage.
The extent of debris is shown in the third photo.
While I'm at it, here are some other helpful bits:
The Flowmaster kit did not come with flange bolts or the clip nuts. In looking at the old bolts, it was clear they needed to be replaced. I purchased a full set of replacement parts, OEM. I had trouble finding them and found some on eBay. That said, they took two weeks to deliver, charged for shipping for each bolt ($8 per bolt), even though they all came in one sealed package from a Chrysler dealer in California. A tip here is to look at the dealers' parts counters before you go on eBay. I could have saved time and money. This waiting also goofed up my weekend plans. Try to get all the parts you need before beginning work (duh).
Putting the Flowmaster unit back on was not as difficult, but still tricky. The new pipe came in two sections, so it wasn't as heavy, lifting it into place. I bungeed it into place so I didn’t have to lift it while putting in the bolts. Then mated to the exhaust manifold, in a rough-fit fashion so I could align it for the bolts. Although aligning the flanges and seating the pipe to the exhaust manifold took some finesse. I got the flanges mostly aligned and loose-fit the bolts. I tightened the bolts, back and forth, one turn for each bolt to evenly seat the flanges. But you have to get out from under, look from under the hood to see if they're even (Photo 4). Or have a spotter to guide you from up top. I tested it after getting everything bolted in by running the engine and saw some exhaust leaking from the mated flanges. Clearly, I didn’t get them aligned right. So, I loosened all four, and went slowly back at it, getting up and checking up top for good seating.
You can over-tighten and bend the Flowmaster flanges. Be careful and observe the torque requirements.
In between all of that, I was able to get the catalytic converter pipe connected to the twin pre-cat pipe. The U-bolt that connects those two pipes is not as good as other types. Your results may vary, but I had a leak. From the muffler flange, I was able to remove the old cut piece of pipe, and mate the catalytic converter pipe to the muffler. I should have replaced the muffler while I was at it. But honestly, the muffler is much easier to replace and I can do that separately.
The codes cleared, and it drives soooo muuchhhh bettter.
Mark, I am glad I sent you my ECM to fix. So far after 2 weeks the faulty O2 sensor indication has not shown up. You did a great job fixing the circuitry within the unit. I will recommend your company to other folks. Tom Jensen
Those would be H2O sensors
I think the OP is just referring to Heated Oxygen(O2) Sensors.
But seriously, call up WranglerFix for some assistance with the ECM.
Chris, I am glad you recommended Wrangler Fix to me. They did a great job fixing the circuitry within the ECM. Thanks Again. Tom Jensen
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