Never Ending CAT codes

[AggieLC]

So i have had hell with my emissions system. Replaced all sensors and both, yes both catalytic converters (not high flows, good quality cats) at the same time to be done with these check engine lights for good. Well turns out done for good meant about two months. Now check engine lights are back on and P0420 and P0430 Catalyst System Efficiency Below Threshold yet again...... Cool. Well I was wondering what could be causing both cats to go bad. I have aftermarket Doug Thorley Headers on this thing, PO installed. Could they be causing too much heat and burning things up? I have full skids so im sure its toasty under there. Thinking ill go back to stock headers whenever I hit 180,000 and do the service just to be safe. All opinions wanted.

 

[Lucky Strike]

Look at long term and short term fuel trims. For example if a fuel injector is leaking alot of excess fuel, which may have caused the original cat to fail, it'll burn up the new cat too.

Edit - you can find this information in techstream or in a universal obd2 scanner. very high or very low fuel trims can have many causes, so report back what you find.

 

[Spike555]

Here is my experience with those codes, not on my Cruiser, but other cars...weak spark.
Weak spark will not combust the fuel completely sending to much raw fuel into the cats, when the cats are marginal they can't process all the raw fuel, O2's read out of range and it sets off either bad cat or bad O2 codes, or both.

To much raw fuel can also ruin your cats, but I doubt 2 months worth of driving did that to your brand new cats, unless you drove like 20k.

 

[AggieLC]

I'll dig into both of those and report back. Thank you for the guidance

 

[Spike555]

Any update?

 

[2001LC]

So i have had hell with my emissions system. Replaced all sensors and both, yes both catalytic converters (not high flows, good quality cats) at the same time to be done with these check engine lights for good. Well turns out done for good meant about two months. Now check engine lights are back on and P0420 and P0430 Catalyst System Efficiency Below Threshold yet again...... Cool. Well I was wondering what could be causing both cats to go bad. I have aftermarket Doug Thorley Headers on this thing, PO installed. Could they be causing too much heat and burning things up? I have full skids so im sure its toasty under there. Thinking ill go back to stock headers whenever I hit 180,000 and do the service just to be safe. All opinions wanted.

Anytime we deviate from stock things change, is exhaust an issue in your case? Hard to say. But this issue is one happening on stock with no sure resolution yet. P0420 and P0430 - 2006 LC

Can I ask what year 100 series you have?

Are you get a heavy fuel smell from exhaust, during cold start? and after warm up??

Look at long term and short term fuel trims. For example if a fuel injector is leaking alot of excess fuel, which may have caused the original cat to fail, it'll burn up the new cat too.

Edit - you can find this information in techstream or in a universal obd2 scanner. very high or very low fuel trims can have many causes, so report back what you find.

@Lucky Strike could you provide a little more color on how to find this info, what numbers to look for and what are target numbers (optimal)?

 

[crimsonaudio]

both catalytic converters (not high flows, good quality cats)

Some guys have chased this for a long time - it certainly seems the computer likes something about the OEM cats. I used aftermarket, high-flow cats and kept throwing codes. Had my buddy (Toyota master tech) check it out top to bottom, including checking emissions, and he said it's running perfectly, so my choice were to put OEM cats back on (I'm not paying that much for cats) or find another solution.

I went with option #2 and installed some URD sensor simulators and have had zero issues since. In fact, he's so impressed with them that he's started using the URD sims on Tundras with aftermarket cats as well.

 

[2001LC]

On Snowy (no CEL) but as PM I'll be:
Doing Fuel injector rebuild When to replace fuel injectors
Replacing:
Fuel pressure regulator.
Intake manifold gaskets as PM for the VVTi engines. post #56 Just scored a 2007 LC
Both aging PCV hoses.
Spark plugs.
Coolant flush.
All while doing Timing Belt job.

Also gas cap, radiator cap, thermostat along with temp sending unit if any doubt after testing each.

I learned a bit on The Redbaron, number one is issue with intake manifold gasket. These gasket either shrink or have been redesigned, as new OEM's are thicker.
I did not have Fuel Injectors done as I found it had regular on vehicle cleaning at Dealer. But the more I've consider the issue of Fuel Inject's, I felt a very good idea ~194K on Snowy while doing T-belt.
The fuel pressure regulator is something that was recently recommended to another member in mud by FIS (Fuel Injector Specialists - Home - Wheat Ridge, CO). FIS Feels they start going wreaking around 100K effecting MPG. Any reduction in MPG indicate not running at peak performance. The VVti engine seem more susceptible to issues when not at peak performance then pre VVti.

Some guys have chased this for a long time - it certainly seems the computer likes something about the OEM cats. I used aftermarket, high-flow cats and kept throwing codes. Had my buddy (Toyota master tech) check it out top to bottom, including checking emissions, and he said it's running perfectly, so my choice were to put OEM cats back on (I'm not paying that much for cats) or find another solution.

I went with option #2 and installed some URD sensor simulators and have had zero issues since. In fact, he's so impressed with them that he's started using the URD sims on Tundras with aftermarket cats as well.

Do you have any short or even better long term MPG data?

 

[crimsonaudio]

Do you have any short or even better long term MPG data?

I've had the URD sims installed for a year now, zero change in gas milage. Also, no difference in milage from the OEM cats vs aftermarket cats.

 

[jerryb]

this is good info to learn from. Troubleshooting Wideband O2 Sensors

short and long term fuel trim can be read from torque and obd fusion- easier than techstream. I use obd fusion with the toyota (year specific) extras. That's where I look at fuel trims and narrow and wideband voltage. I like fusion better, but torque's display is nicer. You can get pre and post cat EGT temps from fusion also, or others.
Short terms should hover around zero at idle with no load. You can see go up and down with throttle position movements. I've never seen higher than 4. Or lower than negative 5 on over run. My specific long terms are at 8 and 6, as of last week.
This is what I see at least. The manual may have more specific range/limit numbers.
So many things involved, it's mind boggling

fuel pump
exhaust manifold leak
coolant temp sensor
vac leaks below butterfly
coil pack, plugs, injectors, pcv
mass air flow
fuel leak at filter, damper, or regulator
*gas tank temp at +140 degrees- lol

I like the simulator deal, if mine was 15 years old or so and I had problems.

 

[AggieLC]

I thought about doing the simulators, good to hear your good reviews, I'm currently putting business cards over the CEL lights until next year when I do the 180,000 mile service and get it done right, don't have the funds to tackle it at the moment

 

[Spike555]

Some guys have chased this for a long time - it certainly seems the computer likes something about the OEM cats. I used aftermarket, high-flow cats and kept throwing codes. Had my buddy (Toyota master tech) check it out top to bottom, including checking emissions, and he said it's running perfectly, so my choice were to put OEM cats back on (I'm not paying that much for cats) or find another solution.

I went with option #2 and installed some URD sensor simulators and have had zero issues since. In fact, he's so impressed with them that he's started using the URD sims on Tundras with aftermarket cats as well.

So this has me thinking, could a guy use the simulator and then install "test" pipe and still not get a cat code? From what I know about O2 simulators they send a "good" signal to the ECU even when your rear O2's are bad, but URD's description says they use the rear O2's.
Do they use them for looks? Or actual signal?

 

[crimsonaudio]

So this has me thinking, could a guy use the simulator and then install "test" pipe and still not get a cat code? From what I know about O2 simulators they send a "good" signal to the ECU even when your rear O2's are bad, but URD's description says they use the rear O2's.
Do they use them for looks? Or actual signal?

You can use them for a cat-delete (for off-road use only, of course).

They modify the incoming signal from the rear o2 signal to make it look like the cat is working perfectly. They're passive boxes, so they rely on the signal generated by the sensor, so it's not there just for looks.

 

[Spike555]

You can use them for a cat-delete (for off-road use only, of course).

They modify the incoming signal from the rear o2 signal to make it look like the cat is working perfectly. They're passive boxes, so they rely on the signal generated by the sensor, so it's not there just for looks.

So when the sensor fails completely it will have to be replaced then, but in that case a El Cheapo O2 would be just fine so who cares.

 

[crimsonaudio]

So when the sensor fails completely it will have to be replaced then, but in that case a El Cheapo O2 would be just fine so who cares.

I think this would be the case. I have relatively new secondly O2 sensors, so I'm not certain, but if I understand how these things work, they just need a signal to regenerate and output the signal fooling the computer.

 

[FLWookie]

Quick Question: Which side is Bank 1 and Bank 2? I'm getting a CEL for faulty O2 sensor Bank 2 rear.
Thanks.

 

[jerryb]

bank one is drivers side.