P0420 and P0430 - 2006 LC

[camino70]

I have several options, including buying used cats from cruiserparts.net, or putting in these: Underdog Racing Development

How about something like this Amazon.com: O2 Sensor Spacer Adapter Extender: Automotive

Edit:
As Recruiser mentioned below, this may work with upstream O2 sensors, but will not work with the downstream O2 sensors that have a flange, my apologies.

 

[RECRUISER]

How about something like this Amazon.com: O2 Sensor Spacer Adapter Extender: Automotive

Great resource, tons of positive reviews. Based on reviews sounds like there's a 90% chance that this would be a permanent fix for the P0420 and P0430 codes. About $15 - 17 dollars per side. If my PCV valve tinkering doesn't permanently fix my codes this will be my first option. Thank you for your feedback this could help A bunch of people out!

 

[RECRUISER]

Oops won't work with my 2003. My sensors aren't screw in, they have a flange with two screws.

 

[2001LC]

Running engine with synthetic oil reduce PCV fouling.

Side note: I just pick up a 2007 w/172k miles, and noticed the mouth of the throttle body is spot less. I know at 156K miles it had a Dealer fuel injector cleaning, so they probably wiped T-body. What I found interesting is the amount of caked on grim inside the intake manifold. It also had a bit caked on out side on lower (6") half of intake ports. The front of the head covers had very little seepage if any, certainly not enough to account for grim on outside of intake ports. Makes me think the plastic attracts petroleum gunk. I've looked in cast aluminum intakes with 300K mile, poorly maintained and using convention oil that looked cleaner.

The heavy build-up inside intake, leads me to believe using the gas with the most cleaner additives, a can of 44K in the fuel tank before each oil change, syntactic oil and clean PCV valve every oil change may be best practice with the VVTi 4.7.

Head covers (AKA valve cover) gasket looks good and tight along bottom and back side. Not a drop of oil.

Yet, lower area of intake ports up about 6" are grimy.

 

[sean2202]

I used to clean my pcv valve in simple green until I had a plugged one on a previous vehicle and that caused a slew of problems. Now I just replace them every 15K or so. Fuel filter as well... change that thing regularly ( if easily excessable) Do the simplest things first. Poor quality fuel can run havoc on vehicles especially something that may be very sensitive to begin with. I like the idea of "self cleaning" a cat. That's how we keep our chimney clean burn it hot, a slow fire will have alot more buildup!

 

[RECRUISER]

Good information Sean2202 and wisdom to take care of the simple inexpensive things first. And to even revisit things after they've been done, in my case my PCV valve was fine for only 100 miles before failing to close again causing my code to reappear. but because after cleaning the PCV I saw a change in the pattern of lights coming on I hoped I was on to something and went back over my work to recheck and found PCV still wasn't closing fully - probably my incomplete job of cleaning the valve to begin with. New one is on order.

 

[KYLandy]

Okay, so I'm continuing to investigate this. I have completed the following work:

• Replaced leaking intermediate exhaust pipe
• Replaced A/F sensors
• Replaced O2 sensors
• Cleaned MAF
• Replaced PCV valve
• Checked spark plugs (all new)
• Ran a bottle of Cataclean in the fuel tank (2 times)
• Replaced Air filter
• Tested EVAP system using TS (passed all tests)
• Checked for manifold leak (only visually)

I know the cats are bad, but I am trying to identify WHY they are bad. My latest theory involves a rich mixture. My A/F sensors are supposed to operate at 3.3 volts. Both have been replaced with new. Yet, my sensors are still reporting 3.23 volts at idle and the voltage for the O2 sensors is 0.68 to 0.70. It is my understanding that a low A/F sensor voltage indicates a rich mixture. I would like to know if anyone else who has bad cats is getting the low A/F sensor voltage or if your idle voltage is higher than mine. My fuel trims are near zero so it doesn't look as if the computer is reacting to the possibly low A/F voltage. I'm not sure what is causing the possibly rich mixture but I only get around 10 MPG driving in the city (about 2 miles of about 13 stop lights to work each day). Since the total fuel trims look good, I am not sure what is really going on with the mixture. My injector on time is around 2.68 ms which I believe is within spec.

I know that the A/F voltage is supposed to constantly flip flop from rich to lean and back so that the cats can absorb oxygen (while lean) to use in the catalyst reaction. I don't see the switching in the TS software but it may be due to how frequently it samples the voltage. Here's the graph:

Here's the voltages:

I'm sure if this is what caused the cats to go bad or not, so I want to get some expert feedback on the A/F voltages before I replace the cats. I am not getting any codes other than the P0420 and the occasional P0430. Clearly, the computer does not see anything wrong with the voltages but it still worries me.

Thoughts?

 

[aging fleet]

Hey, not sure if it's a helpful benchmark, but I took a few snapshots from my 110k mile '06 with all original sensors, cats and no history of throwing emissions codes.

Regarding a/f voltages, mine bounced between 3.24 and 3.30 during screen refreshes.

 

[KYLandy]

Hey, not sure if it's a helpful benchmark, but I took a few snapshots from my 110k mile '06 with all original sensors, cats and no history of throwing emissions codes.

Regarding a/f voltages, mine bounced between 3.24 and 3.30 during screen refreshes.

View attachment 1405983

View attachment 1405984

This is much appreciated! It looks like the A/F voltages are within range of yours. However, I am concerned about your O2 sensor voltages. It's my understanding that they should be between 0.4V and 0.55V. This is from the 2006 FSM for running the injection volume test and shows when the mixture becomes rich and when it becomes lean. I believe that your O2 sensors might be modified with inserts or some other device. How long have you owned that LC? The PO may have done something to your O2 sensors like installing the URD simulators. Very weird!

 

[aging fleet]

How long have you owned that LC? The PO may have done something to your O2 sensors like installing the URD simulators.

I've had it about 2.5 years. I'm the second owner and the lady who had it before me had all scheduled and non-scheduled maintenance done at the Lexus dealer in her town. Can't explain the low voltage values, but I'd be surprised if she knowingly circumvented any system.

If I/we are interpreting things correctly, this would mean I'm running lean and would expect to see higher exhaust gas temperatures. Not sure if that would translate into higher cat temps, but that something I could check.

 

[aging fleet]

I hooked it back up tonight and the voltage for the OS2s stayed at zero for about a minute or two then the voltage began to climb. I'm sure it has something to do with the warmup cycle. Anyway, after running for about 4 minutes, here are what my readings looked like.

 

[jerryb]

you guys made me want to go find out if I could log while under load. Which I'm still not sure. But I recorded two sections of time in the driveway anyway, but it outputs a file that's more like a notepad txt file that's worthless.
Anyway I looked at idle, 25xx and 35xx rpms. In all instances with no load the readings are basically the same.
I'm not use to doing wideband sensor stuff on NA, closed loop vehicles.

First, I'd do all the things that kylandy did, but include all injectors, starting with the 4 on bank 2. Buy 4 new and send the 4 off to test, refurbish, get a report on. When you get the used 4 back, install them on bank 1. Send the second 4 off to keep later as spares. That's just me though. I'd also buy all new coils just because. I start at the front and work backwards to the muffler. I do mean the front of the car/truck.

If i was faced with stuffed cats as a final determination, and being in the south, I would gut them with a pinch bar and reinstall and retest. AS a last resort. If I didn't know if they were good or bad-- before breaking out the torch to burn bolts and visually inspect them-- I would block off the PCV penetrator and extend the hose to dump on the ground and zip tie it, and retest. Then gut the cats, or buy a bypass pipe and go the simulator route. I think it's kind of pointless to do the run around with the closed loop system that toyota has here. Fix it as cheaply as you can, cut corners when you have to.
Absolutely buy the same/like quality toyota OEM wide and narrow band sensors. MY six pack is empty now. Good Day.
Let me say that I'm not anywhere near an experienced guy with this, only with what I've done in the past. I've only had the truck since oct.

 

[KYLandy]

Looks like your readings are about the same as mine. I can confirm that my sensors are in spec. I found this online at TIS for my 2006:

 

[KYLandy]

So, I am not running rich it appears. I can cross that off the list. There certainly isn't any smell associated with a rich mixture.

I think I'm going to have to call this one: I don't believe the conditions that caused the cats to go bad are currently present. That means it is probably safe for me to replace the cats. However, the low fuel mileage worries me. I run 93 octane (U.S.) and my mileage still is around 10 mpg in the city.

 

[KYLandy]

I hooked it back up tonight and the voltage for the OS2s stayed at zero for about a minute or two then the voltage began to climb. I'm sure it has something to do with the warmup cycle. Anyway, after running for about 4 minutes, here are what my readings looked like.

View attachment 1406257

That looks much better. Sheesh! I thought maybe I had a different problem. thanks for doing that. All of this really helps understand what is and what isn't normal.

 

[KYLandy]

I have all of the normal conditions for the engine variables in this PDF. It is for 2006 made after 5/2005 so there may be some differences between this and those made before that. I have attached the PDF to this message.

 

[RECRUISER]

In your search for rich mixture (incomplete combustion) why don't you to go ahead and change ALL 8 spark plugs even though you said they were new looking, if you didn't personally check all 8?. I am very impressed with your thoroughness and competence so please don't take this suggestion wrong, if you haven't already.

Unless you changed them yourself and/or inspected them all yourself there could be a couple towards the firewall even that were never changed at all? I have seen even new spark plugs give trouble And are they all gapped correctly ( mine were all at .060 and guarantee they were causing a problem along with my PCV) possibly overwhelming my cats over many many miles.

Keep me updated as you find your problem.

 

[KYLandy]

I already have the plugs ready to go in but didn't want to risk messing up a coil or two in the process. It may be worth a shot. It was definitely in my list of things to do but I don't have any misfires. I would think a bad plug would have to log a misfire at some point but it could just be an incomplete burn. Then again, the A/F sensor would detect a rich mixture. Based on the others voltages that were posted, I don't see that my mixture is rich. Voltages between 2.8V and 3.8V are normal, so there is nothing to indicate a rich mixture. Like you said, might as well give it a shot.

 

[RECRUISER]

interestingly enough although my plugs were very old looking and all gapped way too wide, I did not have a single misfire code ever.

 

[2001LC]

Agree, I don't think you'd get a miss-fire code with marginal spark plug(s), the plug would need to fail IMHO. But as spark plug gap widens, it would require/draw on a greater spark to fire properly, which the coil would deliver. This, I've suspected for some time now, will cause overheating of coil. It's well documented that heat is the killer of coils. I've been planning on testing this plug to coil relation, but have lacked the time and equipment as of yet.

I'd not be concern in the least with removing coils. I do it all the time to inspect and clean spark plugs. I've done it on 300K miles 20 year old rigs with signs of overheating, without any damage to coil, wires or spark plug(s).