P0420 and P0430 - 2006 LC

[KYLandy]

Your downstream 02's are way off though, was everything up to temp?

The DTC that was set last night was the output of the ECU monitoring NOT the Control Injection Volume test that I can run manually. I was driving to the store last night after work when the MIL came on. This means that the computer examined the conditions for the test and decided to run the monitoring whereupon it triggered the DTC code. The data above is from the freeze frame data that the ECU stored when it triggered the code.

 

[DirtDawg]

Once again if anyone is having these issues and doesn't feel like spending money on guessing:

If all else fails: Underdog Racing Development

I went through a similar process on my 4R and never found the issue. Even though it was a 3.4 v6, the concept is the same. I believe the issues on these later engine 100's is due to the location of the O2 sensors.

 

[Julian Stead]

Can you read the voltages live on the oscilloscope screen at idle, the downstream shouldn't oscillate up and down but remain steady. Going below the voltage threshold on downstream means there is to much oxygen in the CAT, if you are sure there is no vacuum leak and your PVC is good, then you should look at fuel pressure. Your LTFT will normally change to compensate for this. If you haven't had a fuel filter change it wouldn't hurt to get it replaced, also disconnect the battery for 30mins and then let idle for 15mins to reset ECM. If your downstream continues to fluactuate up and down then the CATS are probably gone.

 

[Julian Stead]

If it is pointing towards the CATS in the end. I would still drop them off and see if they have broken up inside. You can sometimes hear them broken up by hitting the side of the cat with side of your fist.

 

[crimsonaudio]

I replaced both (shot) OEM cats with aftermarkets about a year ago and have had random P0420 and P0430 codes thrown since. My Toyota tech bud told me these aftermarkets are probably a bit more 'open' (not as environmentally clean) as the OEMs and therefore I'm getting the codes, so I bought one of the URD O2 sensor simulators (plug and play, super easy) since the only thing the rear O2 sensors do is measure the cleanliness of the air, and while it's only been a few days, zero codes.

So all in all I'm about $900 out of pocket instead of ~$2500 for new OEM cats.

 

[KYLandy]

I read a post on another Toyota site that stated that Toyota made their vehicles (after a certain point) 50 state legal and that their cats are 90% efficient compared to aftermarket Federal cats (non-CARB) which are about 75% efficient. This might be why these codes get set more often and why they don't last as long. Thoughts?

 

[DirtDawg]

I read a post on another Toyota site that stated that Toyota made their vehicles (after a certain point) 50 state legal and that their cats are 90% efficient compared to aftermarket Federal cats (non-CARB) which are about 75% efficient. This might be why these codes get set more often and why they don't last as long. Thoughts?

While that may be true, I also believe that toyotas required o2 readings are too strict.

 

[2001LC]

Just throwing this out as some food for thought.

But first a question, do any of you that are having this issue track gas millage manually? I so what is you MPG and have you seen any long or short term changes???

Some thoughts:
As I've said I don't like just throwing parts at a problem. I also agree, especially IF both CATS have gone bad, cause needs to be found.

That said:
Considering the suggestion it has to do with the newer design, possible to do with placement of o2, you think we see many more 05-07 with issue. But possible this is a combination of issues like CAT design, Air Pump, fuel injector out of spec (dirty or bad spray pattern), charcoal canister, return fuel system, topping off gas tank, high altitude and changes in elevation. Some or all combine to give bad CAT code or even causing CATs to go bad. Could be the small allowable variance in manufacturing and some 100 system are more sensitive (as @DirtDawg has suggested). Then possible this newer CAT design is just to sensitive for the combination in some 100's as they age.

I don't know if this will work (plug and play). But what if someone with both CATS showing bad, swap with one older model CATS & o2 as a test. This MAY help confirm or rule out CATS design. Any thoughts on this idea, will it plug & play (bolt on & o2 work)?

Note: I found three part numbers for these 100 series: 98-02, 03-05 & 05-07 (05 was probable early & late runs).

 

[DirtDawg]

@2001LC It makes me wonder if since the sensor is placed in the cat instead of after on the later models, that the cats haven't had enough time to do their job before the O2 sensor picks up a reading? Once again just spit balling here.

But at the same time I agree that if this was the root cause we would be seeing more cases.

 

[Julian Stead]

If both CATS have indeed gone bad then there sure is a root cause thats needs to be found and rectified, as the new CATS will go bad aswell. Have there been any issues past or present that could of help destroy the CATS? Loss of coolant/oil, misfires, egr faults etc. All past and present faults would have to be considered.

 

[KYLandy]

So, I have been posting in another thread What octane do you run? because I was experimenting with running 91 octane to see if it cleared up my codes returning. It did not, although it seemed to help delay the code for a few miles which makes me think spark plugs might be an issue as well. My theory is that with 91 octane, the computer can advance the timing and make the engine more efficient while 87 octane will tend to make it less efficient and perhaps leave more unburned fuel heading towards the cats. I'm due for spark plugs, so it won't hurt anything to change them.

I did notice that the only code that consistently gets thrown is P0420. When I checked it tonight, it was the only one and P0430 wasn't pending. It passed with an Oxygen Storage Capacity (OSC) score of 0.233 (.155 being the minimum). The P0420 did not pass with a score of around 0.14, IIRC. If spark plugs don't help then I will replace the Bank 1 cat and see how long that gets me.

I still haven't identified any existing problem that would have caused the cats to go bad. There is nothing in the Toyota dealer history that would suggest a problem that would lead to poisoning the cats except the spark plugs having 114k on them. No coolant problems, Heated oxygen sensor, Intake air temperature sensor, Mass air flow meter, Crankshaft position sensor, Engine coolant temperature sensor or other problems noted.

I am not yet fully convinced that the 87 octane did not play a role in poisoning the cats, though. It definitely runs better on 91 and when this tank is empty I am going to run some 93 octane in it and compare the OSC results.

Stay tuned!

 

[KYLandy]

So, as a part of my strategy to get caught up on all of the maintenance that was neglected by the PO, I decided to clean the MAF sensor last night and reset the ECM. It was an easy 5 minute job that anyone can do. I wanted to see if cleaning the MAF sensor would improve the throttle response which seems to lag a tiny bit when you accelerate quickly. I removed the negative battery cable before starting the job and left it disconnected for 30 minutes. I then let it idle for 15 minutes to relearn and then took a test drive. The throttle response was significantly improved and the power increase was noticeable. An interesting side effect of all of this was that the cats passed the Catalyst Efficiency Test during the test drive. The B2 side passed with flying colors although I am curious as to why the minimums are different between the 2 sides. Since I have only been getting the P0420 code lately, it could mean that the B1 side cat is really the only one going bad. I'll drive some more over the next few days and then take another look at the test results to see if they have changed. The improvement could be due to a cleaner MAF, resetting the ECM or both. Either way, I think I may have narrowed the problem a little bit by isolating the B1 cat as being the bad one. If so, then I have reduced my immediate cost by 50% if I have to replace it. Still haven't received the spark plugs yet, so I am hoping that I see more improvement in the catalyst efficiency results after I change plugs. It never hurts to hope. Besides, the plugs need changing anyway. Below are the result prior to cleaning the MAF sensor and after (not the same day):

Results before cleaning MAF:

Results after cleaning MAF:

 

[2001LC]

Seems like @Chance has worked through a minor tune-up, without issue being correcting. But then perhaps everyone not dealing with same issue.
Or
Perhaps the new newer CATs & o2 placement is just super sensitive. Bad gas & engine in need of a minor tune-up fouls the CAT's & o2's just enough to set off codes. A minor tune followed by a CAT & o2 cook-off / cleaning may be beneficial, certainly can't hurt. This cook-off could be the missing piece.

By minor tune I mean:
Not all inclusive and assumes all fluid (oils', coolant) change/flushes are up to date and coolant system has passed inspection. It's important to eliminate the simple stuff before moving on. This has been covered but worth repeating.

1. Remove EFI fuse. Then crank engine to relieve fuel pressure. (If replacing fuel filter)
2. Disconnecting battery (negative post first), cleaning & greasing both post. Leave battery disconnected (for minimum of 30 minutes), to rest ECM. NOTE: The very last thing you do is reconnect battery.
3. Replace fuel filter. Put EFI fuse back in.
4. As you remove air box; Clean MAF sensor with a spray can of MAF Sensor Cleaner & inspect air filter. Don't touch thin internal wires or get anything like grease or oil on them. Use a little dielectric grease on connection in hardness.
5. Inspect all vacuum hoses for cracks and tight fit.
6. Remove PCV and soak in solvent.
7. Clean throttle body in place. I use Sea Foam lube, tooth brush & brass brush along with dental type mirror to clean. Avoid getting excessive amounts of solvent like sea foam lube into axle holes of butterfly. Some feel this can damage throttle body motor/gears.
8. Test and replace PCV (air passes one direction only). PCV Grommet on pre 2003 must have tight fit or replace. Replacing both PS & DS PCV hose if loose fit.
9. Remove spark plugs, inspect, clean & test or replace. Use spark plug cleaner, test resistance & gap. Note: Do not change gap of used plugs. A little dab of dielectric grease where coil meets the spark plug, is nice touch. If a compression test is to be performed move this to top of list along with pulling EFI fuse, as it must be done with engine hot.
10. Re torque valve covers to factory spec.
11. Reassemble in reverse order.

Cook off CATs & o2's:

Drive at high RPM for 5 minutes, normal RPM 5 minutes then repeat. I use a lower gear to drive on HWY at ~4,800 RPM. This heats up exhaust systems, much like turning one's oven to clean mode.

There is also CAT & o2 chemical cleans that claim to do a great job. I've not tried them.

 

[KYLandy]

If anyone is interested in the calculation for Oxygen Storage Capacity (OSC) this patent explains how it works. I like to study things like this so I know exactly how the Catalyst Efficiency Test works and how the score is derived. My day job is that I work as a data analyst so this is right in my wheel house. I'm still trying to understand the calculation myself so I am not an expert (but I sometimes play one on TV).

 

[2001LC]

Cool.

 

[Chance]

Seems like @Chance has worked through a minor tune-up, without issue being correcting. But then perhaps everyone not dealing with same issue.
Or
Perhaps the new newer CATs & o2 placement is just super sensitive. Bad gas & engine in need of a minor tune-up fouls the CAT's & o2's just enough to set off codes. A minor tune followed by a CAT & o2 cook-off / cleaning may be beneficial, certainly can't hurt. This cook-off could be the missing piece.

By minor tune I mean:
Not all inclusive and assumes all fluid (oils', coolant) change/flushes are up to date and coolant system has passed inspection. It's important to eliminate the simple stuff before moving on. This has been covered but worth repeating.

1. Remove EFI fuse. Then crank engine to relieve fuel pressure. (If replacing fuel filter)
2. Disconnecting battery (negative post first), cleaning & greasing both post. Leave battery disconnected (for minimum of 30 minutes), to rest ECM. NOTE: The very last thing you do is reconnect battery.
3. Replace fuel filter. Put EFI fuse back in.
4. As you remove air box; Clean MAF sensor with a spray can of MAF Sensor Cleaner & inspect air filter. Don't touch thin internal wires or get anything like grease or oil on them. Use a little dielectric grease on connection in hardness.
5. Inspect all vacuum hoses for cracks and tight fit.
6. Remove PCV and soak in solvent.
7. Clean throttle body in place. I use Sea Foam lube, tooth brush & brass brush along with dental type mirror to clean. Avoid getting excessive amounts of solvent like sea foam lube into axle holes of butterfly. Some feel this can damage throttle body motor/gears.
8. Test and replace PCV (air passes one direction only). PCV Grommet on pre 2003 must have tight fit or replace. Replacing both PS & DS PCV hose if loose fit.
9. Remove spark plugs, inspect, clean & test or replace. Use spark plug cleaner, test resistance & gap. Note: Do not change gap of used plugs. A little dab of dielectric grease where coil meets the spark plug, is nice touch. If a compression test is to be performed move this to top of list along with pulling EFI fuse, as it must be done with engine hot.
10. Re torque valve covers to factory spec.
11. Reassemble in reverse order.

Cook off CATs & o2's:

Drive at high RPM for 5 minutes, normal RPM 5 minutes then repeat. I use a lower gear to drive on HWY at ~4,800 RPM. This heats up exhaust systems, much like turning one's oven to clean mode.

There is also CAT & o2 chemical cleans that claim to do a great job. I've not tried them.

Thanks for the info. I'll try the cook off and maybe the chemical clean of the cook off doesn't change anything. I've done all of what you listed up to the cook off. If this doesn't work, im going to try the spacers and then move to some electrical tape over the light

 

[Julian Stead]

Has anyone knocked the CAT with a rubber mallet or side of fist to see if it has broken up inside, or even removed for visual inspection. I would still use the oscilloscope pattern to check CAT efficiency, If the downstream 02 sensor is fluctuating up and down fast, then the CAT has gone bad. No amount of cleaning or tuning can reverse this, once the CAT is gone it's gone. If the downstream pattern is steady but reads high or low then you can look upstream to improve the reading as the CAT is doing its job, just not efficient enough. Get your exhaust gas tested to confirm your emissions are high.

 

[2001LC]

Thanks for the info. I'll try the cook off and maybe the chemical clean of the cook off doesn't change anything. I've done all of what you listed up to the cook off. If this doesn't work, im going to try the spacers and then move to some electrical tape over the light

Remember to disconnect battery for 30 minutes after.

Has anyone knocked the CAT with a rubber mallet or side of fist to see if it has broken up inside, or even removed for visual inspection. I would still use the oscilloscope pattern to check CAT efficiency, If the downstream 02 sensor is fluctuating up and down fast, then the CAT has gone bad. No amount of cleaning or tuning can reverse this, once the CAT is gone it's gone. If the downstream pattern is steady but reads high or low then you can look upstream to improve the reading as the CAT is doing its job, just not efficient enough. Get your exhaust gas tested to confirm your emissions are high.

True, dead cat is dead cat. But we're seeing here replacement cats go bad. Both cats indicate bad then only one. It's very unlike (as we've both noted) two go bad at same time without something else going on.

That said; I agree, it would be nice to physically have these verified as dead.

 

[Julian Stead]

Sorry I didn't mean to come across as saying they are bad so just replace them, just to confirm whether they are good or bad. It is just get confirmation what your up against, as in good CAT with CEL or bad CATS with CEL. If the new CATS have both gone bad then I would address that issue then.

 

[KYLandy]

I am more focused on why the cats are bad (if that is truly the case) rather than replacing them. As I said before, it won't do any good to replace them if you don't know why they went bad in the first place. While I can identify with your frustration, I think that my problem is more complicated than just fixing it.

To your point, I have studied the waveform and run the active rich/lean test but I can't get the cats to fail that way. The dealer even did a tailpipe test and said that it failed. There are other reasons why it can fail an emissions test that have been pointed out already. The question remains: why did my cats fail?

Sometimes my cats pass the efficiency test and other times they don't so that concerns me. The OP replaced his cats and it didn't solve anything so I don't want to spend $4k on new cats just to have the same problem. Aftermarket cats aren't going to work in my case. I will still have random codes being thrown. I am only going to use OEM cats if I need to replace them.

Besides, banging on something with a mallet is not a very reliable way to judge anything. I prefer a more scientific approach. As agonizing as it may seem, I really need to understand this system thoroughly before making any decisions. I hope you understand that this is exactly what I am trying to do.