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i would clear the codes and see if it comes back again.
P0420 and P0430 - 2006 LC
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i would clear the codes and see if it comes back again.
I just replaced the 2 downstream sensors this past weekend and it completely fixed my problem. Both sensors were warped from the heat.
My comment "they seem set on throwing parts at the issue, regardless of anyone's suggestions" was off color and uncalled for. I was just have a bad day! SORRY.
You've really been working hard through some tough issues. Keep up the good work and good luck.
You've really been working hard through some tough issues. Keep up the good work and good luck.
Also, I replaced my downstream O2 sensors with Denso 234-4209 and I have the same MY 2006 vehicle that you do. Is that the part number you installed in your most recent post?
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No worries at all and no apologies are in order. I understand when helping someone over the net it can be frustrating when someone continues to encounter the same issue yet they won't do the simple troubleshooting stuff. In my case, I did not have time to properly troubleshoot it so I just took it to Mountain States Toyota and they said cat replacement. I went ahead with it as I didn't have a better option and figured that they knew what they were doing and went with their suggestion. After the MIL remained, I was pretty annoyed at myself for having listened to the tech/SA at Mountain States. Since cats were new I figured it couldn't hurt to change out the oxygen sensors upstream and downstream as others have had success. Now that those items are eliminated and are in working order, I will move to others items as suggested and hope for some success. All in all @2001LC I do sincerely appreciate your help, comments and knowledge as you have posted in this thread. The only reason that I am documenting my hurdles is for someone down the road experiencing this issue to refer back to this thread and maybe cut down the learning curve that I am currently in pursuit of.
@KYLandy I replaced 2x 234-4260 and 2 x 234-9051. I visited the Denso website and the 234-4209 is the universal one while the 234-4260 is labeled as OE style.
I will be getting at it again this weekend again with a multimeter and techstream (got it loaded). Other thoughts and suggestions are most welcome.
Here's a photo of the old O2 sensors and the new Denso 234-4209. I don't know how much more OEM you can get. They aren't identical, but my lights are off and have not returned. The bottom one is the new one that I installed and it works fine. You can also see how warped the top ones (old) are and why they were the problem.
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That's what they told me, too, but they were wrong. They always take the most expensive route and it never solves the real problem. In my case, I chose to ignore them and trust the forum guys who said 90% of the time those codes are downstream O2 sensors. They were right and it saved me a ton of money. The dealer was going to charge me over $8,000 to do all of the repairs (almost $4,000 just to replace the cats) that I did to mine for less than $500. Something to think about.
Okay, so I must have angered the automotive gods because my codes came back tonight after 205 miles of trouble free driving. Before the O2 sensor replacement, the codes would come back after 24 miles or so. Time to keep working the problem. Maybe my cats really are bad. Performance does not seem to be suffering, though. I had bad cats on an F250 and the engine wouldn't even run because they were so clogged. How can a meticulously serviced 10 year old vehicle have bad cats? I'm thinking that it's still something else. I have changed the air filter. Next will be PCV valve and possibly clean the MAF sensor.
This sucks!
This sucks!
Any thoughts on how they became warped?
My guess is too much heat for too long. With 114k on the meter, I wouldn't expect them to last much longer than that. However, I am starting to think my thermostat might be bad based on what I have read in this thread. If the engine is running too cool then too much fuel is passing through the engine leaving too much unburned fuel getting into the cats. I believe that this would make the cats run hotter than they should and therefore the excessive heat would warp the O2 sensors. I'm going to connect it to Techstream tonight and monitor the engine temperature to see if there is an issue. I'll monitor the O2 sensor voltages for problems, as well.
Good quality o2's last a very long time, in properly running engine, 144K is barley broken in.
A "rich" condition (excessive fuel to air mixture) lowers cylinder temp, and may cause buildup of fuel residue on o2's (fouling). A fouled o2's that then became excessively hot will cook off residue. One way I clean CATS and o2's is to run engine at ~4,500+ RPM while driving for 5 or 10 minutes. This is akin to turning ones oven to clean setting. It will turn residues to a white flaking dust that will just blow out the exhaust system.
I'm in doubt your exhaust pre, post or in CATS got so hot it would cause that warping. I've never seen this, have run a Google search and can't find any case like this. Looks more like they were bent by force, accidently or purposefully. Any work previously done in area i.e. replace exhaust manifolds, head gasket or exhaust pipe etc..?
I've only owned the vehicle a little over a month but ALL service marks were hit consistently at a Toyota dealership by the one owner before me. If there was a problem with the engine that caused this, I can't imagine that it would have been missed by the Toyota tech. However, the problem remains. I have seen warpage like this on an exhaust manifold, though, but it was due to design of the manifold. I have a 1997 Ford F350 7.5L that warped the y-pipe near the manifold in much the same way. The 7.5L motors were notoriously bad in their exhaust restriction. Basically, Ford tried to pass emissions by restricting the exhaust so much that the heat buildup would eventually warp the manifolds and break manifold studs. The y-pipe flange actually wrinkled in the same way these O2 sensors wrinkled when they cooled down. I had an exhaust shop cut out the flange and weld a new one in to fix the problem until I put the Banks kit (headers and exhaust) on the 7.5L. No problems since. I still believe that the warpage on the sensors is heat related. It looks like that to me. When I purchased the LC, the codes weren't set but could have been cleared by the non-Toyota dealership I bought it from.
It just seems weird that the codes would come back after 24 or so miles before I replaced the O2 sensors and now it takes 200 or so miles for the codes to set. Changing the O2 sensors did something related to the problem but I'm not sure what. Seems to me that if you put functioning sensors in while the cats were bad, the problem would show up in a shorter time frame with the "clean", non-fouled sensors. The Toyota tech I took it to after I first bought did an emissions test and concluded that the cats were failing. I suspect that it failed the emissions test because the computer is not adjusting the AFR correctly due to problems with one of the many related inputs.
I should be able to identify any coolant temperature problems with Techstream tonight and will post the results. What are the main data points from Techstream do I need to look at other than O2 sensor voltages and coolant temperature?
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Status update:
Pullled plugs to see how they looked. They didn't look horrible, but I decided since this was a new to me LX with 150k miles, I would go ahead and put new plugs in. Codes are still there. Next on the list is the PCV valve, mostly bc it's fairly cheap and some people have had success with exchanging it. If that doesn't work I'm going to give up and put in the O2 sensor spacers. If that doesn't fix the problem I'm going to put some electrical tape over the check engine lights.
Pullled plugs to see how they looked. They didn't look horrible, but I decided since this was a new to me LX with 150k miles, I would go ahead and put new plugs in. Codes are still there. Next on the list is the PCV valve, mostly bc it's fairly cheap and some people have had success with exchanging it. If that doesn't work I'm going to give up and put in the O2 sensor spacers. If that doesn't fix the problem I'm going to put some electrical tape over the check engine lights.
Look at your fuel trims to see if your running lean.
If all else fails: Underdog Racing Development
Ran it on my 4R with great results as I was having similar problems with no solution in sight.
Ran it on my 4R with great results as I was having similar problems with no solution in sight.
If that doesn't fix the problem I'm going to put some electrical tape over the check engine lights.
What bothers me most about these codes is that the VSC is disabled. I want that to work! So, my OCD propels me to diagnose this issue and fix it. I am in a non-testing area so I could gut those cats and put in the non-foulers or the ones above.
On another note, my downstream O2 sensors are in the cats, not downstream from the cats. I don't have flanges on my downstream sensors. They just screw right into the cats. The 2004 FSM shows the Three Way Cats (TWC) with the flanges. I guess they must have changed the design in 2006.
Unfortunately not everyone has included year, make, model and mods to their signature....... "HINT"...
It seem each 100 series in this thread with same codes are either 2006 or 07. This indicates a year specific issue. Possible pointing to timing or air pump, which are most apparent difference I can think of. One other issue I don't think we've touch on is fuel quality. Low octant, alternatives fuel (ethanol and such) added to gasoline should also be considered.
@Chance, PCV valve usually just need a good cleaning with solvent. The PCV hoses (DS & PS) do however go bad around 100K (7yr) and should be replaced. Good idea to double check all vacuum lines while at it.
@KYLandy, Hopefully someone experienced with tech stream will help with your question.
Business end of your "warped" o2's look pretty normal, but with just a little more white then I'd like to see. I'd think such high heat internally as to warp external part, business would have looked very different. Something like this:
It seem each 100 series in this thread with same codes are either 2006 or 07. This indicates a year specific issue. Possible pointing to timing or air pump, which are most apparent difference I can think of. One other issue I don't think we've touch on is fuel quality. Low octant, alternatives fuel (ethanol and such) added to gasoline should also be considered.
@Chance, PCV valve usually just need a good cleaning with solvent. The PCV hoses (DS & PS) do however go bad around 100K (7yr) and should be replaced. Good idea to double check all vacuum lines while at it.
@KYLandy, Hopefully someone experienced with tech stream will help with your question.
Business end of your "warped" o2's look pretty normal, but with just a little more white then I'd like to see. I'd think such high heat internally as to warp external part, business would have looked very different. Something like this:
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Good News. No more P0430 now only dealing with P0420. @Julian Stead Lamda is 1 (close to it). The downstream oxygen sensor on bank 1 is reading super low voltage (attached pic) from the new denso sensor. So to eliminate the sensor, the plan is to swap the downstream sensor from bank 1 to bank 2 and bank 2 to bank 1. If it switches to a P0430 that means I just need to order a new sensor. If that does not resolve the issue then looking into exhaust leaks as mentioned above in @Julian Stead post. I have heard cracked headers on other cruisers and this one is not cracked (no ticking at cold start). Upstream oxygen sensors were replaced so ruling that one out. So at this point, narrowed down to 3 things:
1. Bad oxygen sensor (downstream bank 1)
2. Exhaust Leak (unlikely but will be checked nonetheless)
3. Vacuum leak
Onwards to the "Mud Brain Trust" I am uploading pictures of the techstream data please let me know if I am missing anything:
View attachment 1353331