O2 Sensor Issues
02-01-2010, 01:39 AM
#1
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O2 Sensor Issues
I Recently got a check engine light "0420: Catalyst system efficiency below threshold - bank 1" I am trying to figure out where these O2 sensors are located how many are there and what exact parts I need to do the repair.
02-01-2010, 02:38 AM
#4
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http://oxygensensors.com/catalog.php?&pkey=1430774 get the second one down its 77 dollars, this is the secondary o2 sensor (bank 1 sensor 2) it is located in the spipe( the pipe that goes under the oil pan and over the axel) the sensor is located on the pipe just before it goes over the axel and is an easy replacement
02-01-2010, 02:40 AM
#6
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do you even know what it looks like?
okay, pop the hood, you are not looking at your engine. there should be a heat shield there, follow the exhaust manifold under the head shield between the radiator fan shroud and fans, you'll see a sensor connected to a wire coming out of the exhaust manifold. that is the first O2 sensor.
the primary catalytic convertor should be in the exhaust manifold just below the primary o2 sensor. after the catalytic converter, there is a pipe shaped like an "S" (which is why it is called the S-pipe. there is a secondary o2 sensor there.
now, from what i read up on this code, the problem can be the o2 sensor(s) or the catalytic converter. so rather than just blindly replacing these things until the CEL goes away, get it diagnosed.
okay, pop the hood, you are not looking at your engine. there should be a heat shield there, follow the exhaust manifold under the head shield between the radiator fan shroud and fans, you'll see a sensor connected to a wire coming out of the exhaust manifold. that is the first O2 sensor.
the primary catalytic convertor should be in the exhaust manifold just below the primary o2 sensor. after the catalytic converter, there is a pipe shaped like an "S" (which is why it is called the S-pipe. there is a secondary o2 sensor there.
now, from what i read up on this code, the problem can be the o2 sensor(s) or the catalytic converter. so rather than just blindly replacing these things until the CEL goes away, get it diagnosed.
02-02-2010, 11:45 PM
#7
p0420 is actuall indicating the catalyst in in the convertor is weakening that means u need a ne catalytic convertor not o2 sensors one way to make sure it is not the o2 sensor is to watch the voltage on the downstream o2 if it is reacting or jumping around than the downstream (second o2) is fine it is the catalytic convertor but u need a scan tool for this another way is to go out and drive it at highway speeds so the catalyst gets hot enough if the light goes out it is definetly the catalytic convertor a lot of people bring me cars with this problem and think it is the o2 sensor but indeed the o2 sensor is doing its job and telling u the cat is slowly failing the downstrem o2 is the o2 that collects the data for the efficiency of the catalytic convertor. DONT YOU LOVE EMISSIONS
02-05-2010, 10:59 PM
#8
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The secondary o2 sensor would be bad if it is not functioning (no voltage, through a short or an open circuit), but like it has been said above a p0420 is a bad cat code. 80% of the time this is the problem.
Check your wave form for the secondary o2, what is it doing? if you can't check that, take it to someone that can unless you want to needlessly replace parts.
Check your wave form for the secondary o2, what is it doing? if you can't check that, take it to someone that can unless you want to needlessly replace parts.
06-02-2010, 06:22 PM
#9
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p0420 is actuall indicating the catalyst in in the convertor is weakening that means u need a ne catalytic convertor not o2 sensors one way to make sure it is not the o2 sensor is to watch the voltage on the downstream o2 if it is reacting or jumping around than the downstream (second o2) is fine it is the catalytic convertor but u need a scan tool for this another way is to go out and drive it at highway speeds so the catalyst gets hot enough if the light goes out it is definetly the catalytic convertor a lot of people bring me cars with this problem and think it is the o2 sensor but indeed the o2 sensor is doing its job and telling u the cat is slowly failing the downstrem o2 is the o2 that collects the data for the efficiency of the catalytic convertor. DONT YOU LOVE EMISSIONS
I have the 0420 CEL also and I just hit 90k miles. Of course that means no warranty on the cat, so I am hoping I am in the small percentage where it really does mean O2 sensor. One thing I never heard though is what you said above (in red). I drive all highway 5 days a week, definitely highway speeds (or more), 60 miles/day and my light has never gone off. So should that really give me hope that it might NOT be the cat and a much cheaper O2 sensor would be the fix?? I mean how likely is it that it could be the cat still and the light would not go off under those circumstances. I have had no other strange symptoms since the light came on like other people usually have.
06-03-2010, 11:11 PM
#10
well u might get lucky but nine times out of ten when i see this in the shop i end up replacing the cat and walla do u have a scan tool where u can watch the secondary 02 if u want to be cheap and kinda ghetto you can use a cel eliminator like they use on aftermarket headers that would make the 02 read slightly leaner which in return might trick the ecu into thinkin the catalyst's efficiency has improved and turn the cel off just spit ballin
06-03-2010, 11:47 PM
#11
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Dude.... punctuation.... words .... 
It is not just leaner, it is the waveform it expects to see from one O2 compared to the other (rate of change, etc).
Did you install a header recently?
Have you checked the wiring to and from the sensor?
Have you checked to see if the readings from the sensor with a voltmeter or diagnostics tool at least make some sort of sense?
Make sure you have a bad part before replacing one. If it is under warranty (emissions warranty is longer) and you have not modded it, take it to the dealer. If not, and you are not comfortable with doing the troubleshooting yourself, take it to a good private mechanic
It is not just leaner, it is the waveform it expects to see from one O2 compared to the other (rate of change, etc).
Did you install a header recently?
Have you checked the wiring to and from the sensor?
Have you checked to see if the readings from the sensor with a voltmeter or diagnostics tool at least make some sort of sense?
Make sure you have a bad part before replacing one. If it is under warranty (emissions warranty is longer) and you have not modded it, take it to the dealer. If not, and you are not comfortable with doing the troubleshooting yourself, take it to a good private mechanic
06-04-2010, 01:25 AM
#13
Sorry. I just think faster than i can type. If it is a stock setup except cold air the first o2 is going to be reading the way a stock motor would. Therefore the second o2 if it is working properly would read a more emission friendly non ozone polluting afr if the catalyst is doing its job correctly. So if you were to get the second 02 sensor to see around a stoich burn in the exhaust the cel would not be there hence the cel eliminator. It will pull the o2 away from the exhaust stream far enough to read a slightly leaner afr making the ecu think the catalyst is working properly. But that is only if the secondary o2 is reading properly thats why i asked if he had a scan tool to watch it so he can see the changes himself to make the call.
08-20-2010, 07:11 PM
#14
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This is what I got at emissions :
P0420:Catalyst system efficiency bellow threshold bank 1
P0441:Evaporative Emission System Incorrect Purge Flow
P0455: Evaporative Emission System Leak Detected (largeleak)
P0456: Evaporative Emission System Leak Detected (very small leak)
KOEO Result : FAIL
MIL Command Status : FAIL
Any Help on What could be the Issue here?
P0420:Catalyst system efficiency bellow threshold bank 1
P0441:Evaporative Emission System Incorrect Purge Flow
P0455: Evaporative Emission System Leak Detected (largeleak)
P0456: Evaporative Emission System Leak Detected (very small leak)
KOEO Result : FAIL
MIL Command Status : FAIL
Any Help on What could be the Issue here?
08-23-2010, 01:45 AM
#17
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ANyone know how much that cost, we replaced the gas cap with just a replacement cap (not toyota OEM but another aftermarket company) and its still causing a issue. Would a toyota cap vs someone else be something we could try out ?
