Hello! I was wondering if someone could give me advice about what to do with my car. I have a 2000 Corolla with about 98k miles on it. The check engine light went on so I bought an OBD II reader and checked out what the code is and it said P0420. I brought it to the mechanic and he said it is the catalytic converter and is going to cost $1350 parts and labor to replace. He said that normally you could get non-manufacturer parts but in this case he had 2 people come back within six months after replacing the cat with a non-manufacturer catalytic converter and it had to be replaced again. He said since he had those bad experiences with non-manufacturer parts, he would only put in a Toyota brand cat and that would cost me $1350. He said if I want an aftermarket part I have to go elsewhere. Has anyone else heard of problems using non-manufacturer parts when replacing the catalytic converter? I don't want to replace it once only to have to replace it again in a couple of months. Is $1350 a normal price for replacing the cat? What should I do? Any advice would be appreciated.
TheWheel
The Toyota OEM cat is going to pretty expensive. You might be able to get one from an online retailer for much less than $1350 - but it will be more than most aftermarket cats.
Aftermarket catalytic converters lifespans will depend on who made them and their quality. I have seen some aftermarket cats last 100K miles no problem, I've also seem them die at less than 10K mile or less.
What I would be more concerned about is the P0420 code. That only indicates that the downstream O2 sensor is reading a voltage that "looks" like the upstream O2 sensor - i.e., the catalytic converter "appears" to be bad. I'd say in 9/10 of those codes - the catalytic converter is fine - it is the O2 sensor that is not reading correctly. The mechanic should have backprobed the sensor and verified the ouput on an o-scope. Possible that the upstream (pre cat) or downstream (after cat) are lazy - meaning they are still working, just not as well as they should. Being "lazy" instead of outright failing, also causes them NOT to set a CEL for a bad O2 sensor.
If your car tends to consume a bit of oil - might also be worthwhile to check into that issue. Many of the additives in motor oil and supplemental motor oil additives, tend to kill catalytic converters very quickly. Many manufacturers have started to remove those additives to extend catalytic converter lifespan, but it turns out that those same additives are very good at protecting the engine.
Aftermarket catalytic converters lifespans will depend on who made them and their quality. I have seen some aftermarket cats last 100K miles no problem, I've also seem them die at less than 10K mile or less.
What I would be more concerned about is the P0420 code. That only indicates that the downstream O2 sensor is reading a voltage that "looks" like the upstream O2 sensor - i.e., the catalytic converter "appears" to be bad. I'd say in 9/10 of those codes - the catalytic converter is fine - it is the O2 sensor that is not reading correctly. The mechanic should have backprobed the sensor and verified the ouput on an o-scope. Possible that the upstream (pre cat) or downstream (after cat) are lazy - meaning they are still working, just not as well as they should. Being "lazy" instead of outright failing, also causes them NOT to set a CEL for a bad O2 sensor.
If your car tends to consume a bit of oil - might also be worthwhile to check into that issue. Many of the additives in motor oil and supplemental motor oil additives, tend to kill catalytic converters very quickly. Many manufacturers have started to remove those additives to extend catalytic converter lifespan, but it turns out that those same additives are very good at protecting the engine.
Wheel you could ask that mechanic if he could check the o2 sensor like fish explained. He'd likely be willing to do it. I think he was telling the truth in preventing problems for both of you. If he refused and insisted you needed a cat converter then I'd be willing to say he was trying to do you wrong but so far I dont see it. I'd try him again before the dealer any day. My dealer quoted $1800 to replace mine. I walked.
Btw the magnaflow sounds like a good option if no one thinks you'll have to replace it in two years judging from their experiences with them.
Btw the magnaflow sounds like a good option if no one thinks you'll have to replace it in two years judging from their experiences with them.
Can anyone please post their experiences with aftermarket converters in the gen 8th Corolla? (Magnaflow, Eastern, Catco, etc...)
Did it bring the P0420 code back?
How many miles it lasted?
I need to change my cat (P0420) and I was wondering if there are any good alternatives to the $2000 OEM converter.
Thanks a lot.
Did it bring the P0420 code back?
How many miles it lasted?
I need to change my cat (P0420) and I was wondering if there are any good alternatives to the $2000 OEM converter.
Thanks a lot.
I don't remember the exact part number per say since it was almost 3 years ago.
But I'm sure you can easily find the one that fits your car here, then google up the cheapest price
http://www.car-sound.com/
Mine was a direct-fit bolt-on OEM replacement.
But I'm sure you can easily find the one that fits your car here, then google up the cheapest price
http://www.car-sound.com/
Mine was a direct-fit bolt-on OEM replacement.
Just had a code po420 in the boy's '01 Chevrolet Corolla (Prizm). CEL first came on while driving home after buying the car. Took it back, they replaced the cat with a magnaflo. 2 days later, same CEL-same code. Took it back, replaced bank 2 sensor. 2 more days, CEL again. Gave up & took it to have bank one sensor replaced....that's all that's left, correct? CEL light still came on. Had it scanned by my friend who knows a guy at a shop kind of thing. He said cat was bad. I couldn't believe it. Finally after much discussion & promises, cat was changed to an OEM and CEL stays off. Maybe just got a bad one, but there you go.
Ok, so I was finally able to fix the P0420 code on my 2001 Corolla. From online searches this seems to be a common problem on 98-02 Gen 8th Corollas that reach 80,000 miles or more.
NOTE: Please beware that I am not a certified automotive technician and I do not recommend you do any of the steps written below. If you get a check engine light, you should take your car to an automotive shop with certified professional mechanics where they give you a warranty on any work done in your car. The log below is for information only and to help anyone who experiences a similar problem than mine. Read and do at your own risk.
Background:
I got my car used with 109K miles. After driving it for ~300 miles I got the famous P0420 code. No other codes present. Also, my car had a weird engine noise when going uphill at low speeds (20-40 mph). Sounded like pinging/knocking. I decided to let the car run through some fresh gas and injector cleaners before chasing this matter any further (solution to this was found and explained below)
So before taking that catalytic converter out and bolting a new one in, and since I had no idea how the previous owner(s) treated the car I decided to take the low hanging fruit approach to fix this issue. Besides, catalytic converter failure is usually a result of something else going wrong in the car (i.e. fuel system too rich/too lean, bad O2 sensors, vacuum leak, coolant leak into engine combustion, silicone poisoning, exhaust leak, etc). Therefore, I wanted to make sure that none of those conditions were there waiting to kill the new converter.
This is the list of things I did before replacing the cat:
- Cleaned MAF sensor with CRC Maf sensor cleaner (the sensor was filthy)
- Cleaned Air intake tube and box
- Replaced Air intake filter with Toyota OEM (old filter filthy as well)
- Replaced spark plugs with Toyota OEM iridium (old plugs very worn)
- Ran 2-3 tanks of gas with fuel injector cleaners (Chevron Techron)
After resetting the P0420 code it would come back between 200 to 300 miles
- Checked for intake vacuum leaks using carb cleaner/starting fluid method (found none)
- Checked short and long fuel trims with OBD2 scanner (working within spec)
- Checked for exhaust leaks with car parked and engine running (found none)
- Monitored coolant reservoir level to make sure It was not leaking into engine (coolant level never changed)
- Checked O2 sensors with OBD2 tool and seemed to work within specifications (O2 Sensor#1 would fluctuate rapidly between 0.1 to 0.9 volts and O2 Sensor#2 would fluctuate at slower rate between similar voltages). I compared the sensor plots to my Camry and their response seemed to be normal (i.e.no lazy sensors)
- Checked the O2 sensors heater elements with ohmmeter (working within spec)
- Removed O2 sensors for inspection and they looked structurally ok. Sprayed them with CRC QD electronic cleaner, which is supposed to leave no residue (Warning!!!: this may damage O2 sensors. I did it because I was planning to change the sensors if failure occurred).
P0420 re-appears more often between 80 to 100 miles
- I decided to remove the catalytic converter/resonator assembly for inspection. The catalytic converter inlet honeycomb substrate looked clean and in good shape. There was a thin layer of soot in the pipe not any different of that seen in the tail pipe of cars in perfect working condition. Also, I inspected the outlet side of the converter with a tiny mirror and light through the O2 sensor boss. It looked just like the inlet side. No carbon built-up or substrate damage.
- After bolting on the old catalytic converter assembly back to the car, I turn the engine on and to my surprise I hear an exhaust leak coming from the exhaust manifold at the engine bay. Upon closer inspection, I discovered that in fact there was a leak on the spring-loaded joint at the manifold-downpipe assembly. I take everything back apart, and removed O2 Sensor#1 and the bolts and springs that hold the downpipe. To my surprise, the spring-joint gasket was worn to the core. Since this spring-loaded joint is made to move as the engine rocks (acceleration/brake), it was causing an intermitent exhaust leak. This is why, when going uphill at 20-30 mph the automatic transmission downshifts, the engine would rock normally and the bad gasket would allow exhaust gases out producing a noise reminiscent of pinging/knocking. I bought a new gasket at Toyota dealer and assembled everything back together. Pinging/knocking/leak noise on uphill was gone for good.
P0420 now re-appers between 20-30 miles
- I connected my OBD2 scanner, warm up the car and set to record both O2 sensor#1 and O2 sensor#2. Once warm, I hold the throtle at ~2500 RPM for about 30 seconds to light off the cat. I checked the plots and O2 sensor#2 is mirroring the O2 sensor#1 voltage, which would mean that the catalytic converter is not doing 100% of its job. Therefore, I decided to look for a new catalytic converter.
I decided to search for a direct bolt-on replacement rather than cutting the old converter off and weld a new one in. The reason for this is so I could go back to the OEM converter assembly if the catalytic converter was not the real cause of P0420. I read that a bad ECM or an ECM needing a flash update are also causes of P0420.
My car is equipped with an OBD2 California emissions system (I live in Georgia). After doing some research, I discovered that these systems are supposed to be strict on catalytic converter performance and heard many horror stories on how nothing but an OEM catalytic converter would fix this code.
The Toyota OEM catalytic converter can be purchased for ~$1300. This is probably the best part available for the vehicle in the long-term. However, it was not an option for me due the short-term cost.
I searched Magnaflow's catalog for a direct-fit replacement. They have two options: PN 23881, and PN 46881. I called their tech support and asked them if any of those would work on my OBD2 Calif Corolla. The guy told me that PN 23881 (~$200 online retail) would not work. He said I had to get PN 46881 (~$400 online retail)
I called Eastern Catalytic tech support. I asked the guy if their direct-fit converter PN 40243 would work on an OBD2 Calif Corolla. He told me it will work. Since Eastern has 5 years and 50,000 mile warranty I decided to give them a try. Also, at ~$200 it was an economical option. (Keep in mind PN 40243 is 49-State legal, so it may not be legal in your State. Consult your State laws and the catalytic conveter manufacturer before purchasing)
- Replaced converter with the Eastern direct-fit converter. It came with a gasket for each end of the assembly. The pipes were mandrel bent and it looked of good quality. As opposed to the OEM system, the new system was split in two parts to be connected in the middle by an u-clamp. I assembled the two halves and compared length and orientation to old OEM assembly before installing back to the car. I got M8x1.25x30mm bolts and washers for the muffler end because the flange of new assy was thicker and the bolt-holes larger than stock. I had difficulty making the system leak tight at the middle u-clamp joint, I wish it had a better fit and/or leak tight connection with gasket. Also, be prepared to hear a subtle higher tone on your exhaust as compared to the OEM assy (due to different resonator/less restricted flow?)
It has been 1000 miles and no P0420 code, no Check Engine Light. Car passed Georgia emissions test with flying colors.
6/22/2011 Update: 10000 miles, running great and no P0420 code
NOTE: Please beware that I am not a certified automotive technician and I do not recommend you do any of the steps written below. If you get a check engine light, you should take your car to an automotive shop with certified professional mechanics where they give you a warranty on any work done in your car. The log below is for information only and to help anyone who experiences a similar problem than mine. Read and do at your own risk.
Background:
I got my car used with 109K miles. After driving it for ~300 miles I got the famous P0420 code. No other codes present. Also, my car had a weird engine noise when going uphill at low speeds (20-40 mph). Sounded like pinging/knocking. I decided to let the car run through some fresh gas and injector cleaners before chasing this matter any further (solution to this was found and explained below)
So before taking that catalytic converter out and bolting a new one in, and since I had no idea how the previous owner(s) treated the car I decided to take the low hanging fruit approach to fix this issue. Besides, catalytic converter failure is usually a result of something else going wrong in the car (i.e. fuel system too rich/too lean, bad O2 sensors, vacuum leak, coolant leak into engine combustion, silicone poisoning, exhaust leak, etc). Therefore, I wanted to make sure that none of those conditions were there waiting to kill the new converter.
This is the list of things I did before replacing the cat:
- Cleaned MAF sensor with CRC Maf sensor cleaner (the sensor was filthy)
- Cleaned Air intake tube and box
- Replaced Air intake filter with Toyota OEM (old filter filthy as well)
- Replaced spark plugs with Toyota OEM iridium (old plugs very worn)
- Ran 2-3 tanks of gas with fuel injector cleaners (Chevron Techron)
After resetting the P0420 code it would come back between 200 to 300 miles
- Checked for intake vacuum leaks using carb cleaner/starting fluid method (found none)
- Checked short and long fuel trims with OBD2 scanner (working within spec)
- Checked for exhaust leaks with car parked and engine running (found none)
- Monitored coolant reservoir level to make sure It was not leaking into engine (coolant level never changed)
- Checked O2 sensors with OBD2 tool and seemed to work within specifications (O2 Sensor#1 would fluctuate rapidly between 0.1 to 0.9 volts and O2 Sensor#2 would fluctuate at slower rate between similar voltages). I compared the sensor plots to my Camry and their response seemed to be normal (i.e.no lazy sensors)
- Checked the O2 sensors heater elements with ohmmeter (working within spec)
- Removed O2 sensors for inspection and they looked structurally ok. Sprayed them with CRC QD electronic cleaner, which is supposed to leave no residue (Warning!!!: this may damage O2 sensors. I did it because I was planning to change the sensors if failure occurred).
P0420 re-appears more often between 80 to 100 miles
- I decided to remove the catalytic converter/resonator assembly for inspection. The catalytic converter inlet honeycomb substrate looked clean and in good shape. There was a thin layer of soot in the pipe not any different of that seen in the tail pipe of cars in perfect working condition. Also, I inspected the outlet side of the converter with a tiny mirror and light through the O2 sensor boss. It looked just like the inlet side. No carbon built-up or substrate damage.
- After bolting on the old catalytic converter assembly back to the car, I turn the engine on and to my surprise I hear an exhaust leak coming from the exhaust manifold at the engine bay. Upon closer inspection, I discovered that in fact there was a leak on the spring-loaded joint at the manifold-downpipe assembly. I take everything back apart, and removed O2 Sensor#1 and the bolts and springs that hold the downpipe. To my surprise, the spring-joint gasket was worn to the core. Since this spring-loaded joint is made to move as the engine rocks (acceleration/brake), it was causing an intermitent exhaust leak. This is why, when going uphill at 20-30 mph the automatic transmission downshifts, the engine would rock normally and the bad gasket would allow exhaust gases out producing a noise reminiscent of pinging/knocking. I bought a new gasket at Toyota dealer and assembled everything back together. Pinging/knocking/leak noise on uphill was gone for good.
P0420 now re-appers between 20-30 miles
- I connected my OBD2 scanner, warm up the car and set to record both O2 sensor#1 and O2 sensor#2. Once warm, I hold the throtle at ~2500 RPM for about 30 seconds to light off the cat. I checked the plots and O2 sensor#2 is mirroring the O2 sensor#1 voltage, which would mean that the catalytic converter is not doing 100% of its job. Therefore, I decided to look for a new catalytic converter.
I decided to search for a direct bolt-on replacement rather than cutting the old converter off and weld a new one in. The reason for this is so I could go back to the OEM converter assembly if the catalytic converter was not the real cause of P0420. I read that a bad ECM or an ECM needing a flash update are also causes of P0420.
My car is equipped with an OBD2 California emissions system (I live in Georgia). After doing some research, I discovered that these systems are supposed to be strict on catalytic converter performance and heard many horror stories on how nothing but an OEM catalytic converter would fix this code.
The Toyota OEM catalytic converter can be purchased for ~$1300. This is probably the best part available for the vehicle in the long-term. However, it was not an option for me due the short-term cost.
I searched Magnaflow's catalog for a direct-fit replacement. They have two options: PN 23881, and PN 46881. I called their tech support and asked them if any of those would work on my OBD2 Calif Corolla. The guy told me that PN 23881 (~$200 online retail) would not work. He said I had to get PN 46881 (~$400 online retail)
I called Eastern Catalytic tech support. I asked the guy if their direct-fit converter PN 40243 would work on an OBD2 Calif Corolla. He told me it will work. Since Eastern has 5 years and 50,000 mile warranty I decided to give them a try. Also, at ~$200 it was an economical option. (Keep in mind PN 40243 is 49-State legal, so it may not be legal in your State. Consult your State laws and the catalytic conveter manufacturer before purchasing)
- Replaced converter with the Eastern direct-fit converter. It came with a gasket for each end of the assembly. The pipes were mandrel bent and it looked of good quality. As opposed to the OEM system, the new system was split in two parts to be connected in the middle by an u-clamp. I assembled the two halves and compared length and orientation to old OEM assembly before installing back to the car. I got M8x1.25x30mm bolts and washers for the muffler end because the flange of new assy was thicker and the bolt-holes larger than stock. I had difficulty making the system leak tight at the middle u-clamp joint, I wish it had a better fit and/or leak tight connection with gasket. Also, be prepared to hear a subtle higher tone on your exhaust as compared to the OEM assy (due to different resonator/less restricted flow?)
It has been 1000 miles and no P0420 code, no Check Engine Light. Car passed Georgia emissions test with flying colors.
6/22/2011 Update: 10000 miles, running great and no P0420 code
I had the p0420 on my 01 corolla. I checked the o2 sensors with a digital volt meter and they were reading almost the same. Meaning the cat was bad. I bought the magnaflow aftermarket universal cat for 180. Had it welded on for 50 bucks. Cleared the code and it never came back. I would say test your u2 sensors first. And if the rate of change in voltage in the downstream sensor is the same as fast as the upstream then cat is bad
2002 Chevy Prizm P0420 Code
A special thank you to Joe68 for the post. I don't think I would have solved this one without your help.
I will try to keep my diagnostic work as short as possible, and follow up with a short conclusion. I have spent a large amount of time researching the P0420. There are pages and pages of information out there. From the resources I looked at it appeared that the issue was one of the following: O2 Sensors, Catalytic Converter, MAF Sensor malfunction, Leaks/Clog in the Exhuast, ECU, or possibly another known issue causing the Catalytic Converter to fail. A year ago inspection rolls around and I had to get it fixed. I buy some new O2s, clear the code, and run it 50 Miles before the check engine light comes back on. At this time, I cleaning the MAF is much cheaper then a new cat, so I get some MAF cleaner. I also go through the exhaust inspecting it for leaks with soapy water. None found, which is great. I clear the code and run it another 38 miles and the codes back again. Getting kind of irrated after driving for two hours and no results. I pull out the OBD and check the fuel trims, they look pretty solid, and O2s seemed to be reading good. Well, I guess the problem is the cat. So, I do some homework and find out some people get away with a cheap cat and most recommend buying OEM. I look at the prices and I just could not reconcile the price of an OEM cat. I decide if I am going to take the risk I might as well get whatever's cheap. I spend roughly $90+tax on a new cat and take it to the good ole boys and get it welded for $40. I'm thinking that now is a good time to reset the check engine and put so miles on it. I get pass 40...50...wooohooo...100 miles. I take it to an inspection place and it fails inspection because of a light bulb (damn, almost had it). Get a bulb, stick it in there, and head back to the shop. Sweet the car passed. Now just less than 2 miles out the shop the check engine light kicks back on. It's my good friend Mr.P0420. About that time I was a little confused. I inspect the welds holding the cat on, it looks like a good job. I give it the bubble test, and it passed with flying colors. Another year rolls around and inspection is due again. I think to myself, crap I might have to buy an ecu and I still won't know if that'll fix it. I was coming really close to getting a shop to solve the problem. I decide to buy stock Spark Plugs, and Direct Fit Stock Rear O2 (maybe the universal ones just suck). Clear the code and keep waiting...42 miles later...boom my good ole friend p0420. Now I'm pissed, what in the frick is wrong with this fricking thing. After reading and reading I decide that maybe that cheap cat just sucked and maybe I should cough up the dough and get the OEM cat, or maybe I should take it to a shop. Well, I decide to do another leak inspection. Everything looks good...wait I feel air coming from somewhere around the cat...I think it's the cat. Guess what? The replacement cat spot weld broke free letting alot of air escape. I notice the rear O2 is reading way below spec voltage. I consider my options, but I always seem to opt for the inexpensive route (if it fails then I will suck it up). I throw on some RTV Silicon to seal up the leak (this is gasket maker stuff). Let it dry and check the exhaust for leaks. Looks good, clear the code and drive the car 50 miles. Check engine still hasn't come up but two monitors incomplete...100 miles...200 miles...250 miles later CATALYST MONITOR Complete. Sweet normally after 50 miles check engine light was back on, but this temporary fix seemed to work. So far it's been driven over 500 miles and looking good.
From my conclusion I believe the issue was the result of using cheap Bosch O2 Sensors and a cheap cat. I have heard bad comments about Bosch's O2's (funny because they invented it). I realize that Denso is the stock manu of the O2's and to alway's opt for a direct-fit O2 (better quality). I also decided that instead of going with a cheap part for something that can get very expensive it's probably best to get something at least midgrade. I Walker or Magnaflow cat would have probably done much better. Remember that your cat normally fails due to a preexisting condition. When I bought the car, I realized the owner hasn't changed the spark plugs in 75,000 miles which contributed to the a misfire. This caused the front O2 to go bad most likely and raw gas to dump into the cat (possibly killing it).
A special thank you to Joe68 for the post. I don't think I would have solved this one without your help.
I will try to keep my diagnostic work as short as possible, and follow up with a short conclusion. I have spent a large amount of time researching the P0420. There are pages and pages of information out there. From the resources I looked at it appeared that the issue was one of the following: O2 Sensors, Catalytic Converter, MAF Sensor malfunction, Leaks/Clog in the Exhuast, ECU, or possibly another known issue causing the Catalytic Converter to fail. A year ago inspection rolls around and I had to get it fixed. I buy some new O2s, clear the code, and run it 50 Miles before the check engine light comes back on. At this time, I cleaning the MAF is much cheaper then a new cat, so I get some MAF cleaner. I also go through the exhaust inspecting it for leaks with soapy water. None found, which is great. I clear the code and run it another 38 miles and the codes back again. Getting kind of irrated after driving for two hours and no results. I pull out the OBD and check the fuel trims, they look pretty solid, and O2s seemed to be reading good. Well, I guess the problem is the cat. So, I do some homework and find out some people get away with a cheap cat and most recommend buying OEM. I look at the prices and I just could not reconcile the price of an OEM cat. I decide if I am going to take the risk I might as well get whatever's cheap. I spend roughly $90+tax on a new cat and take it to the good ole boys and get it welded for $40. I'm thinking that now is a good time to reset the check engine and put so miles on it. I get pass 40...50...wooohooo...100 miles. I take it to an inspection place and it fails inspection because of a light bulb (damn, almost had it). Get a bulb, stick it in there, and head back to the shop. Sweet the car passed. Now just less than 2 miles out the shop the check engine light kicks back on. It's my good friend Mr.P0420. About that time I was a little confused. I inspect the welds holding the cat on, it looks like a good job. I give it the bubble test, and it passed with flying colors. Another year rolls around and inspection is due again. I think to myself, crap I might have to buy an ecu and I still won't know if that'll fix it. I was coming really close to getting a shop to solve the problem. I decide to buy stock Spark Plugs, and Direct Fit Stock Rear O2 (maybe the universal ones just suck). Clear the code and keep waiting...42 miles later...boom my good ole friend p0420. Now I'm pissed, what in the frick is wrong with this fricking thing. After reading and reading I decide that maybe that cheap cat just sucked and maybe I should cough up the dough and get the OEM cat, or maybe I should take it to a shop. Well, I decide to do another leak inspection. Everything looks good...wait I feel air coming from somewhere around the cat...I think it's the cat. Guess what? The replacement cat spot weld broke free letting alot of air escape. I notice the rear O2 is reading way below spec voltage. I consider my options, but I always seem to opt for the inexpensive route (if it fails then I will suck it up). I throw on some RTV Silicon to seal up the leak (this is gasket maker stuff). Let it dry and check the exhaust for leaks. Looks good, clear the code and drive the car 50 miles. Check engine still hasn't come up but two monitors incomplete...100 miles...200 miles...250 miles later CATALYST MONITOR Complete. Sweet normally after 50 miles check engine light was back on, but this temporary fix seemed to work. So far it's been driven over 500 miles and looking good.
From my conclusion I believe the issue was the result of using cheap Bosch O2 Sensors and a cheap cat. I have heard bad comments about Bosch's O2's (funny because they invented it). I realize that Denso is the stock manu of the O2's and to alway's opt for a direct-fit O2 (better quality). I also decided that instead of going with a cheap part for something that can get very expensive it's probably best to get something at least midgrade. I Walker or Magnaflow cat would have probably done much better. Remember that your cat normally fails due to a preexisting condition. When I bought the car, I realized the owner hasn't changed the spark plugs in 75,000 miles which contributed to the a misfire. This caused the front O2 to go bad most likely and raw gas to dump into the cat (possibly killing it).
Had my tested and trusted mech. tell me only his wholesaler of Toyota parts would fit but Rockauto.com and any other OEM and Universal Cats they've had fit problems with. But I fail to believe how his 'wholesaler' can have the only parts that fit! OEM is OEM as is Walker Cats. Is it the inner gasket that's forgotten ? That's replaceable and I can do that. Aside from finding OEM parts what's the stock mfr in the factory delivered Corolla? $1300.00 is the price I continually find from the dealers and yet my '03 Corolla has driven 208K miles on its first Cat so maybe that $1300 is worth it? $420 is the going part cost qouted by my mech with the usual $80.00 in labor. I just cannot believe finding a supplier of new Cats is going to be this difficult.
The non-fouler mod is a good low cost option where it works, but plenty of times, the P0420 code is caused by the converter being clogged up with the oil the engine has been burning. Getting the downstream sensor out of the exhaust might keep the code at bay long enough to pass a smog check, assuming it doesn't fail the other parts of the test.
My experience so far is, the Magnaflow (formerly Car Sound) converters do seem like the best option, given their reasonable cost for the quality you get. The two models they spec for the 8th gen can be welded in place of the factory converter fairly easily.
The bolt-on conveters from other brands also seem to be ok, but the ~$200 price tag for what is essentially a replacement converter with pipes welded to either side and the sensor bung welded on seems to be quite a premium. It's nice to be able to just saw off the front of the middle pipe and bolt on a new converter, but it'd be nicer if it wasn't twice to thrice as expensive as a weld-on replacement.
The thing to watch out for is the Made-in-China converters, both of the weld-on and bolt-on variety. Amazon and ebay are littered with nice, polished universal converters and even some bolt-ons with the design specifically for the 8th gen. It's possible these might work ok, but given the small price difference between the China-made stuff and the USA-made Magnaflow, and all the US laws and regulations about emissions and all that, I'd say it's worth having a converter made to at least Federal standards and with a warranty behind it.
My experience so far is, the Magnaflow (formerly Car Sound) converters do seem like the best option, given their reasonable cost for the quality you get. The two models they spec for the 8th gen can be welded in place of the factory converter fairly easily.
The bolt-on conveters from other brands also seem to be ok, but the ~$200 price tag for what is essentially a replacement converter with pipes welded to either side and the sensor bung welded on seems to be quite a premium. It's nice to be able to just saw off the front of the middle pipe and bolt on a new converter, but it'd be nicer if it wasn't twice to thrice as expensive as a weld-on replacement.
The thing to watch out for is the Made-in-China converters, both of the weld-on and bolt-on variety. Amazon and ebay are littered with nice, polished universal converters and even some bolt-ons with the design specifically for the 8th gen. It's possible these might work ok, but given the small price difference between the China-made stuff and the USA-made Magnaflow, and all the US laws and regulations about emissions and all that, I'd say it's worth having a converter made to at least Federal standards and with a warranty behind it.
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