I have a 98 corolla with 105000 miles on it. My CEL light came on & I got it checked with my mechanic who said it was a P0420 code & I needed to replace my CAT. He quoted me $1300. He suggested that it was an old car & he could reset the ECU & maybe the light will not come back on, I asked him to reset it, but it came back on after approx 100 miles of driving. This all happened during winter months in MA.
I recently got hold of a OBD - II sensor from a friend & deleted all error codes to reset the ECU. After approx 390 miles the CEL light came back on. (if came back on on a day when there was a change in temperature) But after 100-200 miles of driving (I don't remember exact), the CEL light went off
I plugged in the OBD sensor & it still gives me the P0420 code, even though the CEL is off.
The question I have is will it pass emissions test as I do not the CEL on, but I can see the P0420 code when I plug-in in the monitor? I ask this as my Emissions inspection is coming up & wanted to figure out if I need the car fixed before I do inspections or can I do it later.
Any feedback will be appreciated
Thanks
Depends on what test they do for emissions - I know in VA, they will just plug in a handheld scanner and run an I/M test. If any old codes are present, you will automatically fail.
The P0420 and similar codes seem to be pretty common on this generation - most of the time (even with certain emissions/EVAP related codes set), the car will still pass a "sniffer" test, but since the car is OBD-II equipped - they will probably just scan the engine computer.
I have the same problem with my '01.
What are the steps others are taking to diagnose a P0420? Look for exhaust leaks first, then start replacing sensors?
I'm really looking for "fixing a P0420 for dummies", if possible. Obviously just listening to Joe Bob the Mechanic saying to replace the cat first off is stupid, based on reading the forums that's not usually the cause.
So, any help?
If there was a good answer to this CEL code - it would already be posted somewhere. Unfortunantly, each case seems to have different ways to diagnose the issue, different set of conditions that caused the code to appear in the first place.
First thing to keep in mind when dealing with any OBD-II code, if Joe Mechanic plugs in a scanner, reads off the code and says XX part is bad - he didn't do his job. The codes only indicate a chain of logic or certain threshold has been tripped from this offending sensor(s).
P0420 is usually noted as "Catalyst System Efficiency Below Threshold (Bank 1)" - that this means is the downstream O2 sensor (after the catalytic converter) thinks that the cat is not working as efficiently as it should.
A couple of possible issues:
- You truly have a dead converter (very likely if you also have a heavy oil consumption issue as well)
- Ignition timing is off (unlikely)
- Bad tank of gas or weather changes causing problems (usually fixed by resetting the code and waiting for it to come back)
- One or both O2 sensor(s) is(are) lazy or not functioning properly
- ECT sensor (engine coolant temp) is not working correctly
- Damaged exhaust system
- Faulty ECM
Also, many who have gotten the converter replaced, never found the underlying problem that caused it in the first place and many times, the replacement will start flagging the P0420 code. No easy answer on this - just start from the bottom and work your way up to the catalytic converter.
If there was a good answer to this CEL code - it would already be posted somewhere. Unfortunantly, each case seems to have different ways to diagnose the issue, different set of conditions that caused the code to appear in the first place.
First thing to keep in mind when dealing with any OBD-II code, if Joe Mechanic plugs in a scanner, reads off the code and says XX part is bad - he didn't do his job. The codes only indicate a chain of logic or certain threshold has been tripped from this offending sensor(s).
P0420 is usually noted as "Catalyst System Efficiency Below Threshold (Bank 1)" - that this means is the downstream O2 sensor (after the catalytic converter) thinks that the cat is not working as efficiently as it should.
A couple of possible issues:
- You truly have a dead converter (very likely if you also have a heavy oil consumption issue as well)
- Ignition timing is off (unlikely)
- Bad tank of gas or weather changes causing problems (usually fixed by resetting the code and waiting for it to come back)
- One or both O2 sensor(s) is(are) lazy or not functioning properly
- ECT sensor (engine coolant temp) is not working correctly
- Damaged exhaust system
- Faulty ECM
Also, many who have gotten the converter replaced, never found the underlying problem that caused it in the first place and many times, the replacement will start flagging the P0420 code. No easy answer on this - just start from the bottom and work your way up to the catalytic converter.
That's my fear-- I don't want to spend $$$ on replacing a converter that isn't bad. I've cleared the code about six times, it's definitely not a fluke.
My '01 has 84k on it, most converters last longer than that. It doesn't burn any oil, and if the temperature gauge is any indication, the ECT sensor works.
How hard is it to swap out the O2 sensors? I would suspect either those or an exhaust leak... This all started on the next extended drive after I scraped bottom during some road construction. If there's a leak prior to the cat, it will flag this code, correct?
Possible to trigger this code with an exhaust leak prior to the cat - I would start with the exhaust donuts and downpipe, then move back. O2 sensors are too terribly bad to change - the downstream one is a little tougher to get to - wiring is under the front seat and you don't have a whole lot of room in that "tunnel" next to the exhaust pipe. They make a special socket wrench that has a slot down the side to fit over the sensor wire - though you might have enough room to put a open ended wrench on it.
Bikeman982
I would say that if your CEL came back 6 times that you have a problem.
Depending on what your state tests on inspection, you may or may not pass.
In CA it would fail if the light was on, but all they check is the exhaust and visually inspect emission parts.
As long as the CEL was not on, it would pass.
My daughter had the same code on her 1995 and she had the catalytic converter replaced.
It must have been the cause of the CEL, because it went away and also passed smog test.
I would say that if your CEL came back 6 times that you have a problem.
I forgot to mention that the CEL has went off on it's own a couple of times. It just did so this
morning, which reminded me. I don't know if that means anything or not.
Bikeman, when are you going to convince your other daughter to switch to a 'rolla?? Just think about how bad the poor Tercel must feel!
If you drive enough - the CEL will turn itself off, but the trouble code is still stored in memory - unfortunantely doesn't mean that the problem "fixed" itself.
Bikeman982
I would say that if your CEL came back 6 times that you have a problem.
I forgot to mention that the CEL has went off on it's own a couple of times. It just did so this
morning, which reminded me. I don't know if that means anything or not.
Bikeman, when are you going to convince your other daughter to switch to a 'rolla?? Just think about how bad the poor Tercel must feel!
Right now she has the newest year car and that is bragging rights.
Maybe her next car will be a Corolla?
A couple of possible issues:- You truly have a dead converter (very likely if you also have a heavy oil consumption issue as well)
I'm having cat issues as well and have heavy oil consumption. Any explanation of why these two symptoms are related? Is it the back pressure that causes stress on the engine and that burns the oil?
Thanks,
Russkiypenguin
Oil residue coats the internals of the catalytic converter - some of which burns off, the leftover clogs the functional sites on the catalyst, causing reduced performance. Some of the residue in motor oil is also poisonous to catalytic converters - in the past diesel motors oils were discouraged for use in gasoline engines, because of this possiblity of converter damage. Not sure if that is the case still.
As for oil consumption relating to a catalytic converter CEL - those are usually a separate issue. Some years of 8th gen Corollas seem to have a bad rap for oil consumption issues - most stemming from stuck rings to bad oil seals. Though it is very possible that the oil consumption has cause the catalytic converter CEL to pop up, ie. clogged ror poisoned the catalytic converter. If the converter CEL popped up before you noticed any oil consumption - then it might be the ECU getting confused. Those are usually cleared up by resetting the CEL and seeing if it comes back. You could have an exhaust system so clogged up that it causes engine pumping problems (ability to draw in fresh air/fuel charge, while efficiently exhausting the combustion byproducts) - but you should have noticed drivability issues way before that happens (car is hard to start, poor gas mileage, low power, etc.)
Bikeman982
It's too bad the local junkyards and wrecking yards cannot sell used catalytic converters.
It is against the law for them to do it.
There are plenty of cars that come in with cats that look brand new.
There seems to be a monopoly that the dealers (and the Feds) have on these parts.
You can also get a generic one from an auto parts place, but they are not cheap there, either.
Hello. I have a 2003 LE and at 100,000 miles, I also had the CEL with the cat code. I reset the computer numerous times and it always came back. After a TON of research, I found this place out of Texas:
They shipped me a whole new aftermarket (non Toyota) exhaust. It's everything from the downpipe to the muffler flange (not including the muffler). You reuse your old bolts and O2 sensor, but it was well worth it. Yes, it includes a nice new cat as well. Shipped it was just under $400 US. I crawled under the car and had it installed inside 3 hours. I'm very happy. They're legit and if you use Google Earth on their address, it's obvious they're a real company in an industrial park in Texas. If you call, talk to a guy named Tom. He was very cool and knowledgeable. He answered all my questions and was very friendly.
My CEL code went away, I passed Pennsylvania emissions tests, saved a ton of cash, and I had a more throaty sounding exhaust note. Win win win win.
Hope that helps you out!
Mike
I bought my bolt on replacement cat for about $180 from Autozone. Quality is a little shaky compared to the factory equipment I removed, but it works and no more P0420 code.
I had one of the oil burning 1zzfe's, so when I threw this code I pretty much expected the converter to be shot.
