I was just trying to get you to confirm something. The question above has two unknown factors. You want to know why your CATS are bad but you don't know they are bad. Why not just ask yourself are my CATS bad first. I know it's a lot of money and I hope they are good so you don't have to spend 4K. When a CAT goes bad they can break up, It is no point looking at data if the CAT has already turned into a pile of dust within your exhaust(mallet) . I was hoping your exhaust test would pass, what did it fail on, do you now the readings. If you confirm the CATS are bad, just ask what killed my CATS after. You can confirm without replacing. Good luck.
P0420 and P0430 - 2006 LC
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I was just trying to get you to confirm something. The question above has two unknown factors. You want to know why your CATS are bad but you don't know they are bad. Why not just ask yourself are my CATS bad first. I know it's a lot of money and I hope they are good so you don't have to spend 4K. When a CAT goes bad they can break up, It is no point looking at data if the CAT has already turned into a pile of dust within your exhaust(mallet) . I was hoping your exhaust test would pass, what did it fail on, do you now the readings. If you confirm the CATS are bad, just ask what killed my CATS after. You can confirm without replacing. Good luck.
I have no doubt that the cats are not at 100% efficiency, but are they bad enough to need replacing at this moment? Being a 50-state emissions compliant vehicle, I know that the standards are very strict in the ECU on my LC but I can live with a certain amount of pollution if it doesn't affect the drive-ability. In other words, I might be okay just using the rear O2 simulators until performance starts to suffer. But, if the front sensors are aged and not performing correctly, then the whole cat efficiency test is outputting incorrect readings. There is no way for the ECU to know that the front A/F sensors are aged and possibly coated with carbon or something. If they are, then they are filtering the data to the ECU and then the whole system is false. If the A/F sensors are misreading the mixture, then there may not be anything wrong with the cats but it still wouldn't pass an emissions test because the mixture is too rich/lean and overwhelming the catalyst's ability to clean it up. If the problems continues, it will ruin the new cats in a hurry and then I will have an $8k problem.
The patent I posted above talks about the problem with the previous design. The 2012 patent was an invention that claimed to be more accurate because it uses the downstream sensor to start the time interval for measuring OSC as opposed to the previous system which used the upstream sensor to initiate the time interval. My system is the previous system and therefore has a limitation in the accuracy of the OSC score. In other words, my A/F might be "filtering" the data back to the ECU and therefore providing false feedback to the ECU on how much to adjust the mixture. The A/F sensor tells the ECU how close to lambda the mixture is, but if it is not reading accurately, then the recommended fuel trims will be wrong and therefore the downstream O2 sensors will be wrong. It's this kind of knowledge that helps me decide if I should go ahead and replace the A/F sensors first, before I replace the cats, to see if that solved the problem. If I replaced the cats first, then the faulty A/F sensor would destroy the new cats as well. If the A/F sensors are "aged" and filtering the data back to the ECU, then that would explain why everything appears normal and the problem has remained undetected. It could possibly mean that I don't need to replace the cats at all. Here's hoping...
Sorry, I thought you had changed th A/F sensors. You can help prove this by swapping the sensors from one bank to the other.
I haven't got techstream but have used other manufacturers diagnostic equipment. If you can check the injection pulse width you will be able to see if the injectors are open longer or shorter to achieve lambda 1 due to faulty sensor. If the A/F sensor is faulty and causing a rich mixture you will see a longer pulse width to be expected at the injectors on the faulty bank.
In my previous screenshots you can see that the injector pulse width is 2.68 ms at idle and that's within specs. It doesn't change much even though the fuel trims jump around at idle. Even the fuel trims are within specs. I can monitor injector widths at different rpms and that might tell me something else is going on.
If the sensor is filtering the data, it will still be off by a factor of x, so the only real way to know is to clean them or replace them. I can get 2 Denso sensors for $208 so that is on my list to do. I have already replaced the downstream O2 sensors so I know they are good. The voltage ranges are within spec as there is an OBDII test for those that is part of the emissions monitoring. With good O2 sensors and possibly bad A/F sensors, my system might be giving false cat efficiency test results. At least I now have a reason to replace the A/F sensors.
If the sensor is filtering the data, it will still be off by a factor of x, so the only real way to know is to clean them or replace them. I can get 2 Denso sensors for $208 so that is on my list to do. I have already replaced the downstream O2 sensors so I know they are good. The voltage ranges are within spec as there is an OBDII test for those that is part of the emissions monitoring. With good O2 sensors and possibly bad A/F sensors, my system might be giving false cat efficiency test results. At least I now have a reason to replace the A/F sensors.
I used to own a 4way fluke handheld oscilloscope and test leads that I called a bed of nails, these test leads allow you to clamp onto a cable without disconnecting them to get your readings. If a car came in and flagged up these fault codes I would put the leads direct onto the upstream sensor and downstream sensor, also my favourite diag kit, a vacuum gauge would be attached somewhere on the intake. A exhaust gas analyser would also be installed. With the car running at first all you want to make sure is that the engine reaches the appropriate temp and the fuel monitoring goes closed loop. During this time I would of carried out checks with the vacuum gauge, you will be surprised what this simple bit kit can tell you. Then I would read the live data on the diagnostic machine, such as STFT, LTFT, injector pulse width, coolant temp, oxy sensors up and downstream. The injection pulse width again tells you a lot as it is the end result of the fuel strategy. The oscilloscope is a lot more accurate to read the fast signals than the diag machine and clamping a lead close to the sensor you can minimise issues with Wiring and connectors.
With it all in place, if everything was OK upstream, I would expect the voltage on the downstream to be steady at around 0.7volts(not sure about Toyota) . If it fluctuates between 0.1 and 0.9 fast like a standard upstream sensor then the CAT is shot, nothing can be done. If it is steady at 0.5 volts then you stand a good chance of improving the result. The vacuum gauge will tell you if the CAT is blocked, A fluctuating voltage will tell you the CAT has disintegrated. The gas analyser will point out if the exhaust gas is good but the Downstream oxy sensor is faulty. There are so many variables that you cannot explain them all, but the most important bit is that before I spend a £1000 of a customers money I would drop the CAT off and visually inspect it and possibly hit it with a mallet(A more reliable test than you would think). To be honest I haven't seen many CATS go bad as they are so reliable, but they normally will show signs of wear when they do. The science behind the CAT is the same no matter what technology you bolt to it, it will remove oxygen and this is how you monitor its efficiency. I cannot speak for your emission laws as I am not sure about them, but if it failed a exhaust gas test then this issue will have to be addressed not just covered up with a downstream simulator or it won't pass in the future. Whether it passes or fails a simulation test, the most important reading to me would be the downstream voltage signal.
Remember it isn't just sensors, there is also wiring and connectors in this circuit before the ECM itself.
No one said it was easy. 90% of the time it is the sensors but that doesn't make a downstream voltage fluctuate, that is the key info you need.
With it all in place, if everything was OK upstream, I would expect the voltage on the downstream to be steady at around 0.7volts(not sure about Toyota) . If it fluctuates between 0.1 and 0.9 fast like a standard upstream sensor then the CAT is shot, nothing can be done. If it is steady at 0.5 volts then you stand a good chance of improving the result. The vacuum gauge will tell you if the CAT is blocked, A fluctuating voltage will tell you the CAT has disintegrated. The gas analyser will point out if the exhaust gas is good but the Downstream oxy sensor is faulty. There are so many variables that you cannot explain them all, but the most important bit is that before I spend a £1000 of a customers money I would drop the CAT off and visually inspect it and possibly hit it with a mallet(A more reliable test than you would think). To be honest I haven't seen many CATS go bad as they are so reliable, but they normally will show signs of wear when they do. The science behind the CAT is the same no matter what technology you bolt to it, it will remove oxygen and this is how you monitor its efficiency. I cannot speak for your emission laws as I am not sure about them, but if it failed a exhaust gas test then this issue will have to be addressed not just covered up with a downstream simulator or it won't pass in the future. Whether it passes or fails a simulation test, the most important reading to me would be the downstream voltage signal.
Remember it isn't just sensors, there is also wiring and connectors in this circuit before the ECM itself.
No one said it was easy. 90% of the time it is the sensors but that doesn't make a downstream voltage fluctuate, that is the key info you need.
Im having emissions issues on my 07 as well. My downstream 02 remains high on bank 2. dealer I bought it from replaced the downstream sensor and then replaced the cat, and Im still seeing high voltage on my bank 2 downstream sensor and a foul smell coming from the exhaust. Really not sure what to do next... replace upstream sensor? do a tune up?
This is a description of the function of the downstream oxy sensor, not sure if it is the same on a toyota but it is the theory I learnt. technology does evolve and confuse things.
The signal from the downstream oxygen sensor indicates when the catalytic converter is operating efficiently. If the catalytic converter is breaking HC, CO, and Nox into their component parts, the downstream oxygen sensor will display a constant voltage.
In the graph at right, the downstream oxygen sensor voltage stabilizes at about .750 volts, which indicates that the catalytic converter is working efficiently.
When a catalytic converter becomes defective, the signal from the rear oxygen sensor begins to duplicate the switching signal of the front oxygen sensor. The PCM then uses a mathematical algorithm to determine when the downstream signal exceeds FTP standards. If the downstream signal exceeds FTP standards, then the PCM will illuminate the “check engine” light and store one or more diagnostic trouble codes. The algorithm programmed into the PCM is a far more accurate method of measuring catalytic converter performance than any externally applied method.
The signal from the downstream oxygen sensor indicates when the catalytic converter is operating efficiently. If the catalytic converter is breaking HC, CO, and Nox into their component parts, the downstream oxygen sensor will display a constant voltage.
In the graph at right, the downstream oxygen sensor voltage stabilizes at about .750 volts, which indicates that the catalytic converter is working efficiently.
When a catalytic converter becomes defective, the signal from the rear oxygen sensor begins to duplicate the switching signal of the front oxygen sensor. The PCM then uses a mathematical algorithm to determine when the downstream signal exceeds FTP standards. If the downstream signal exceeds FTP standards, then the PCM will illuminate the “check engine” light and store one or more diagnostic trouble codes. The algorithm programmed into the PCM is a far more accurate method of measuring catalytic converter performance than any externally applied method.
What is your fault code?
I have gone a few days without the code since I cleaned the MAF sensor so I connected Techstream again to see if there were any pending codes. There weren't any so I checked the Catalyst Efficiency test results and both cats passed although Bank 1 did just barely.
Because I have the new spark plugs in hand, I decided to pull the number 1 spark plug to see what it looked like:
I'm pretty sure that is not a plug that has seen 114k miles. It looks they were all replaced somewhat recently by its condition. I did not clean it and simply re-installed it. I did not pull the others but I am satisfied that the plugs have been replaced at some point.
I can still replace them all but if it ain't broke, don't fix it. Does anyone think I should replace the plugs after seeing the photo? I've seen plugs that have half the mileage on them and none of them looked as good as the one in the photo. Either the dealer replaced the plugs at some point and didn't notate it in the service history or the PO changed the plugs himself. I can hang on to the plugs and change them if I ever get a DTC code or in another 100k miles but I hate messing with things unless absolutely necessary. Things have a way of breaking for stupid reasons and the stupid reason is usually me!
Because I have the new spark plugs in hand, I decided to pull the number 1 spark plug to see what it looked like:
I'm pretty sure that is not a plug that has seen 114k miles. It looks they were all replaced somewhat recently by its condition. I did not clean it and simply re-installed it. I did not pull the others but I am satisfied that the plugs have been replaced at some point.
I can still replace them all but if it ain't broke, don't fix it. Does anyone think I should replace the plugs after seeing the photo? I've seen plugs that have half the mileage on them and none of them looked as good as the one in the photo. Either the dealer replaced the plugs at some point and didn't notate it in the service history or the PO changed the plugs himself. I can hang on to the plugs and change them if I ever get a DTC code or in another 100k miles but I hate messing with things unless absolutely necessary. Things have a way of breaking for stupid reasons and the stupid reason is usually me!
I would look at cleaning the whole intake system if you got a improvement from cleaning MAF, as poor engine breathing can foul the intake and effect emissions. It may of been mentioned previously but I will go through it again.
Inspect air cleaner and replace if needed.
Clean MAF(already done).
Clean throttle body.
A quick inspection of vacuum hoses.
Change PCV valve if oil is present in throttle body or you can clean them but never I have never tried.
Change oil and filter if not done recently.
I would change the fuel filter if you haven't already.
Disconnect battery for 30mins and then let idle for 15mins.
Add a fuel system cleaner.
Your spark plug looks new so wouldn't replace them.
Inspect air cleaner and replace if needed.
Clean MAF(already done).
Clean throttle body.
A quick inspection of vacuum hoses.
Change PCV valve if oil is present in throttle body or you can clean them but never I have never tried.
Change oil and filter if not done recently.
I would change the fuel filter if you haven't already.
Disconnect battery for 30mins and then let idle for 15mins.
Add a fuel system cleaner.
Your spark plug looks new so wouldn't replace them.
2001LC
SILVER Star
That's a new spark plug, the compression gaskets looks almost too good. I would have gone ahead and inspected all plug the re torque and done compression test.
Great list! I've already completed a few of them including:
Inspect air cleaner and replace if needed. (Done)
Clean MAF(already done).
Clean throttle body. (Will work on this tonight)
A quick inspection of vacuum hoses. (Did that while I had the cover off last night. All is good)
Change PCV valve if oil is present in throttle body or you can clean them but never I have never tried. (I think I have located the PCV valve but need to make sure)
Change oil and filter if not done recently. (Oil looks brand new)
I would change the fuel filter if you haven't already. (Also on my list)
Disconnect battery for 30mins and then let idle for 15mins. (Did this after cleaning MAF)
Add a fuel system cleaner. (I'll consider this but I am apprehensive about this since some can damage cats)
2001LC
SILVER Star
PCV; there is one PCV valve but two hoses. One hose coming off each valve cover, DS has valve.
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DirtDawg
"It'd be alot cooler if you did"
Fixed it for ya
2001LC
SILVER Star
I came across a reported fuel pump issue, while I was reading some old notes on what to look to for in different years. Issue that seem "year specific" that I keep to help me with purchase inspections of 100 series.
In it I had a note on VVTi engines have a potential fuel pump issue that wasn't well documented. There was some indication the pump was changed in late 06 and 07 to correct for a weak fuel pump issue in early 06. I never pursued this, as I've been sticking with 01-02, but worth looking into here for those with VVti.
@Julian Stead you may remember this thread where it was mentioned: Really strong exhaust fumes on my 100.
In it I had a note on VVTi engines have a potential fuel pump issue that wasn't well documented. There was some indication the pump was changed in late 06 and 07 to correct for a weak fuel pump issue in early 06. I never pursued this, as I've been sticking with 01-02, but worth looking into here for those with VVti.
@Julian Stead you may remember this thread where it was mentioned: Really strong exhaust fumes on my 100.
My 06 was built in August 2005 so mine is definitely an early build. No mention of replacement of fuel pump in service history and injector pulse width is within spec. It could have been replaced anyway, though, and that would explain bad cats. I still want to replace A/F sensors, just in case. Great info that is worth considering!
It's worth looking into, if the CATS do need replacing it's not something you can Ignore. I wonder if you cant tell if the newer fuel pump is installed just from a visual inspection.
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2001LC
SILVER Star
I suppose their may be different part numbers on fuel pump.
I point to this as just one more possible clue, it doesn't fully explain as late 06 & 07 this was reportedly corrected.
The trick here may be a fuel pressure test. My thinking is that as vehicle's age fuel system performance degrades. Pump may slightly weaken, bad gas slowing filter and injector becoming plugged. Perhaps along with other "tune-up" issues the VVti with it's redesigned heads & o2 placement is just more sensitive to these aging effects.
I point to this as just one more possible clue, it doesn't fully explain as late 06 & 07 this was reportedly corrected.
The trick here may be a fuel pressure test. My thinking is that as vehicle's age fuel system performance degrades. Pump may slightly weaken, bad gas slowing filter and injector becoming plugged. Perhaps along with other "tune-up" issues the VVti with it's redesigned heads & o2 placement is just more sensitive to these aging effects.
What bothers me is that Toyota did not install a schrader valve for checking fuel pressure. I have a gauge but it works off the valve. The FSM says you need a SST and you have to tap into the fuel lines by removing a hose and installing the SST. What a PITA!
