catalytic converter and oxygen sensor replacement?

Hi, all:

My 2000 Corolla's check was on, and sent to the dealer, here was the
diagnose:
Access ECU, Locate DTC P0420 for catalyst below efficiency
Diagnose catalytic oncverter internally worn
new catalytic converter and oxygen sensor installed $1530.78 plus tax
Recommendation:
Front motor mount worn $219.55

Here are my questions?
1. is "P0420" the diagnose code for the problem?
2. Do catalytic converter and oxygen sensor have to be replaced
together? They were replaced around 33000 miles during warranty, now
the car has 139000 miles on it, what is average lifetime for those
parts?
3. what is "Front motor mount worn", does it have to be replaced?

My car just passed PA inspection two weeks ago, and I like to continue
to drive for antoher year before next inspection, then get rid of it.
Is it safe to drive my car without any fix?

Thanks a lot.

I mean check light was on

<wenmang@yahoo.com> wrote in message
news:1128519527.007601.125160@g14g2000cwa.googlegroups.com...[color=blue]
> Hi, all:
>
> My 2000 Corolla's check was on, and sent to the dealer, here was the
> diagnose:
> Access ECU, Locate DTC P0420 for catalyst below efficiency
> Diagnose catalytic oncverter internally worn
> new catalytic converter and oxygen sensor installed $1530.78 plus tax
> Recommendation:
> Front motor mount worn $219.55
>
> Here are my questions?
> 1. is "P0420" the diagnose code for the problem?[/color]


When the check engine light comes on, the car's computer usually stores a
trouble code. Code P0420 means that the catalyst sytem's efficiency for
bank 1 is below the proper threshold. The Corolla has an in-line 4 cylinder
engine so there is no bank 2 (unlike an engbine with a "V" or horizontally
opposed configuration). Basically it means that the system thinks that the
catalytic converter is not working efficiently. The catalyst in a catlytic
conver does not wear out but it can become coated with contaminants over
time so that the catalyst can't work on the gasses passing over it.
[color=blue]
> 2. Do catalytic converter and oxygen sensor have to be replaced
> together? They were replaced around 33000 miles during warranty, now
> the car has 139000 miles on it, what is average lifetime for those
> parts?[/color]

The catlytic converter and oxygen sensor do not necessarily have to be
replaced together. An O2 sensor that is marginal could give the same
trouble code so the shop is probably covering all possibilities as to the
source of the trouble code.

If good quality gas is used, a catlytic converter should theoretically last
the life of the car. An O2 sensor's life can be anywhere from 60,000 miles
to the life of the car.

I believe that cheap gas can shorten the life of the O2 sensors and catlytic
converter, which is why I try to stick to name brand gas. It helps to get
the exhaust system good an hot every so often by taking it out on the
highway in 3rd gear for a few miles.
[color=blue]
> 3. what is "Front motor mount worn", does it have to be replaced?
>[/color]

The engine is attached to the chassis in 3 places with a rubber block. The
rubber block allows the engine to flex a little and dampens the engine
vibrations that are transmitted to the passenger compartment. The rubber in
the mount sometimes becomes hardened or cracked. This is not a common
problem in Corollas and I would not worry about it unless you get strange
noises when accelerating or shifting from acceleration to braking.
[color=blue]
> My car just passed PA inspection two weeks ago, and I like to continue
> to drive for antoher year before next inspection, then get rid of it.
> Is it safe to drive my car without any fix?
>[/color]
Yes.

--
Ray O
correct the return address punctuation to reply

Thanks a lot, Ray.

What is "sytem's efficiency for bank 1"? I was asked by an exhuast
repair shop for upstream or downstream O2 sensor, which one they were
asking about? I may have them replaced by an exhaust repair shop like
Midas instead of dealer. The other thing is that I am not that handy, I
can do some simple maintainance work, like oil change, front brake
replacement, but how difficult to replace them by myself using after
market parts?

Thanks.

I was also told that my car had two O2 sensor, according to what you
just said, was he mistakenly stating extra O2 sensor?
Ny car is 2000 Corrola VE with 4dr
Thanks.

"Ray O" <rokigawa@tristarassociatesDOT.com> wrote in message
news:a1383$4343f95b$44a4a10d$30238@msgid.meganewsservers.com...[color=blue]
>
> <wenmang@yahoo.com> wrote in message
> news:1128519527.007601.125160@g14g2000cwa.googlegroups.com...[color=green]
>> Hi, all:
>>
>> My 2000 Corolla's check was on, and sent to the dealer, here was the
>> diagnose:
>> Access ECU, Locate DTC P0420 for catalyst below efficiency
>> Diagnose catalytic oncverter internally worn
>> new catalytic converter and oxygen sensor installed $1530.78 plus tax
>> Recommendation:
>> Front motor mount worn $219.55
>>
>> Here are my questions?
>> 1. is "P0420" the diagnose code for the problem?[/color]
>
>
> When the check engine light comes on, the car's computer usually stores a
> trouble code. Code P0420 means that the catalyst sytem's efficiency for
> bank 1 is below the proper threshold. The Corolla has an in-line 4
> cylinder engine so there is no bank 2 (unlike an engbine with a "V" or
> horizontally opposed configuration). Basically it means that the system
> thinks that the catalytic converter is not working efficiently. The
> catalyst in a catlytic conver does not wear out but it can become coated
> with contaminants over time so that the catalyst can't work on the gasses
> passing over it.
>[/color]

Ray,
Can you discuss for the OP, the Upstream and Downstream O2 Sensors, and
whether his car even has them? I don't know if he has the down stream
sensor, and my inclination is to replace the O2 Sensor that is on the
exhaust manifold, which is the upstream sensor.

I agree completely with your advice here, but I'm a bit confused by the
particular code he got. My gut instinct is that this would be a downstream
O2 Sensor, but I don't know that his car has this or not. Since he has the
code, I have to assume he has the parts. I was going to tell him to replace
the O2 Sensor(s) because, like you, I think the CAT should be pretty much a
lifetime item in most cases.

This is one of those times when my shadetree expertise just doesn't cover
what's going on.

The O2 Sensors are parts that you can replace yourself, so to answer your
question, yes, you can take the car to a muffler shop instead of to the
dealer.

The O2 Sensors are generally screwed in place in much the same manner as a
spark plug. There is a special socket wrench (cost is under $10.00) that can
accomodate the wire. The special wrench looks much the same as a spark plug
socket, but has a slot cut in the side for the wire. Simply disconnect the
wire at the connector, and unscrew the old sensor and put the new one in.

I get that you might not be much of a mechanic, but my point is to express
how basic and simple this job is. It's like taking a spark plug out and
putting in a new one. There can be issues of corrosion and heat damage that
can make the job a pain in the ass, but if it goes right, it's really very
simple.






<wenmang@yahoo.com> wrote in message
news:1128529460.478619.203030@z14g2000cwz.googlegroups.com...[color=blue]
> Thanks a lot, Ray.
>
> What is "sytem's efficiency for bank 1"? I was asked by an exhuast
> repair shop for upstream or downstream O2 sensor, which one they were
> asking about? I may have them replaced by an exhaust repair shop like
> Midas instead of dealer. The other thing is that I am not that handy, I
> can do some simple maintainance work, like oil change, front brake
> replacement, but how difficult to replace them by myself using after
> market parts?
>
> Thanks.
>[/color]

<wenmang@yahoo.com> wrote in message
news:1128529460.478619.203030@z14g2000cwz.googlegroups.com...[color=blue]
> Thanks a lot, Ray.
>
> What is "sytem's efficiency for bank 1"?[/color]

A catyltic converter ("cat") cleans up the exhaust gases. If it is not
doing its job because the catalyst is contaminated or coated, the second or
"downstream" O2 sensor will detect this and the computer will turn on the
check engine light.

The Corolla has a 4 cylinder engine, with all 4 cylinders lined up in a row,
referred to as a "bank." This layout is known as an in-line engine. Other
engines have cylinders arranged in a "V" or "H" configuration. Think of a
V-6 or V-8 engine as two 3 or 4 cylinder in-line engines joined at the
bottom in a "V" shape. These engines have 2 rows, or banks of cylinders.

I was asked by an exhuast[color=blue]
> repair shop for upstream or downstream O2 sensor, which one they were
> asking about? I may have them replaced by an exhaust repair shop like
> Midas instead of dealer. The other thing is that I am not that handy, I
> can do some simple maintainance work, like oil change, front brake
> replacement, but how difficult to replace them by myself using after
> market parts?
>
> Thanks.
>[/color]

Your car has two O2 sensors. Sensor #1 (sometimes referred to as the
"upstream" sensor) measures the oxygen in the exhaust as it exits the
engine. The car's electronic control unit ("ECU" or computer) adjusts the
amount of fuel injected into the engine based on what O2 sensor #1 sniffs in
the exhaust.

After the exhaust gas passes through the cat, O2 sensor #2 (sometimes
referred to as the "downstream" sensor) takes another sniff and sends a
signal to the ECU. If the exhaust gas is not clean enough, the ECU assumes
that the cat is not working properly and turns on the check engine light.
It is possible that sensor #2 is not working properly and thinks it is
smelling too much pollutants in the exhaust.

One possibility is that whatever contaminated the catalyst could also
contaminate the O2 sensor, which is why you would need to replace both at
the same time.

Personally, I wouldn't bother with the O2 sensors unless you get another
check engine light after the cat is replaced and the ECU points to one or
both of the sensors.

If you can change the brakes on your own car, you can change the O2 sensors.
Sensor #1 is probably located in the exhaust manifold, visible when you open
the hood. It will be screwed into the manifold with a wire connector coming
out of it and is about the diameter of your finger. Sensor #2 looks just
like Sensor #1 and is located in the exhaust pipe after the cat.
--
Ray O
correct the return address punctuation to reply

"Jeff Strickland" <crwlr@yahoo.com> wrote in message
news:EtednZVDhN8un9nenZ2dnUVZ_s-dnZ2d@ez2.net...[color=blue]
>
> "Ray O" <rokigawa@tristarassociatesDOT.com> wrote in message
> news:a1383$4343f95b$44a4a10d$30238@msgid.meganewsservers.com...[color=green]
>>
>> <wenmang@yahoo.com> wrote in message
>> news:1128519527.007601.125160@g14g2000cwa.googlegroups.com...[color=darkred]
>>> Hi, all:
>>>
>>> My 2000 Corolla's check was on, and sent to the dealer, here was the
>>> diagnose:
>>> Access ECU, Locate DTC P0420 for catalyst below efficiency
>>> Diagnose catalytic oncverter internally worn
>>> new catalytic converter and oxygen sensor installed $1530.78 plus tax
>>> Recommendation:
>>> Front motor mount worn $219.55
>>>
>>> Here are my questions?
>>> 1. is "P0420" the diagnose code for the problem?[/color]
>>
>>
>> When the check engine light comes on, the car's computer usually stores a
>> trouble code. Code P0420 means that the catalyst sytem's efficiency for
>> bank 1 is below the proper threshold. The Corolla has an in-line 4
>> cylinder engine so there is no bank 2 (unlike an engbine with a "V" or
>> horizontally opposed configuration). Basically it means that the system
>> thinks that the catalytic converter is not working efficiently. The
>> catalyst in a catlytic conver does not wear out but it can become coated
>> with contaminants over time so that the catalyst can't work on the gasses
>> passing over it.
>>[/color]
>
> Ray,
> Can you discuss for the OP, the Upstream and Downstream O2 Sensors, and
> whether his car even has them? I don't know if he has the down stream
> sensor, and my inclination is to replace the O2 Sensor that is on the
> exhaust manifold, which is the upstream sensor.
>[/color]

I described the "upstream" and "downstream" O2 sensors in my reply to the
OP. I don't like the terms "upstream" and "downstream" because you will not
find those terms used in a repair manual, just like I cringe when people
call wheels "rims." Look in an auto repair manual and see if there is a
procedure for mounting rims or balancing rims.

I believe that most, if not all, OBD II vehicles have 2 O2 sensors. O2
Sensor #1 provides feedback for fuel mixture and sensor #2 measures
catylitic converter efficiency.
[color=blue]
> I agree completely with your advice here, but I'm a bit confused by the
> particular code he got. My gut instinct is that this would be a downstream
> O2 Sensor, but I don't know that his car has this or not. Since he has the
> code, I have to assume he has the parts. I was going to tell him to
> replace the O2 Sensor(s) because, like you, I think the CAT should be
> pretty much a lifetime item in most cases.
>
> This is one of those times when my shadetree expertise just doesn't cover
> what's going on.
>[/color]

The cat is lifetime in theory. In realty, the catalyst gets coated with
contaminants like soot or residue from burning oil, or contaminants in the
fuel. Taking the car on a highway for a good blowout every so often gets
the cat good and hot and helps clear the pipes, so to speak.

An O2 sensor has a much smaller surface area than the catalyst bed so it
probably doesn't take as much to clog it's "nose."
--
Ray O
correct the return address punctuation to reply

<wenmang@yahoo.com> wrote in message
news:1128530182.273182.319010@o13g2000cwo.googlegroups.com...[color=blue]
> I was also told that my car had two O2 sensor, according to what you
> just said, was he mistakenly stating extra O2 sensor?
> Ny car is 2000 Corrola VE with 4dr[/color]

Your car does have two O2 sensors, one in front of the catalytic converter,
close to the engine (possibly in the exhaust manifold, or just after), and
one after the catalytic converter. The one before the converter is used by
the engine computer to adjust the fuel mixture. The one after the catalytic
converter is used to make sure the converter is working.

Personally, I'd try replacing the O2 sensor after the converter before I
bought a catalytic converter. You really should not need both. If the
converter failed, the O2 sensor after the converter is probably OK, since it
warned you that the converter had failed. If the converter is still OK, then
the sensor after the converter must be bad since it identified the converter
as bad when it wasn't. No reason for both to fail at the same time.

You said you recently passed your states inspection. Did they actually
measure exhaust emission during their test? If so and you passed, I'd be
inclined to think the catalytic converter was OK.

Ed

What if "sensor #2 is not working properly and thinks it is smelling
too much pollutants in the exhaust."? Is there a way to check #2 O2
sensor good or bad first before having CAT replaced? CAT replacement is
so expensive, I hope that I can identify the condition of #2 O2 sensor.

Thanks.
WM

If I replace #2 O2 sensor before replacing CAT, is it possible that the
new O2 sensor get damaged by sniffing too much the "dirty stuff"
because of a bad CAT?

Believe or not, the exact same dealer did the state inspection on the
exact the same car, it passed PA inspection.

<wenmang@yahoo.com> wrote in message
news:1128533209.843732.96400@g49g2000cwa.googlegroups.com...[color=blue]
> If I replace #2 O2 sensor before replacing CAT, is it possible that the
> new O2 sensor get damaged by sniffing too much the "dirty stuff"
> because of a bad CAT?
>[/color]

Possible but highly unlikely in a short period of time (under a mnth).

--
Ray O
correct the return address punctuation to reply[color=blue]
> Believe or not, the exact same dealer did the state inspection on the
> exact the same car, it passed PA inspection.
>[/color]

<wenmang@yahoo.com> wrote in message
news:1128532760.374090.216610@g47g2000cwa.googlegroups.com...[color=blue]
> What if "sensor #2 is not working properly and thinks it is smelling
> too much pollutants in the exhaust."? Is there a way to check #2 O2
> sensor good or bad first before having CAT replaced? CAT replacement is
> so expensive, I hope that I can identify the condition of #2 O2 sensor.
>
> Thanks.
> WM
>[/color]

To check O2 sensor operation, you will need a volt/ohm meter or
oscilloscope.

Start the engine and let it warm up to operating temperature, turn
accessories off.
Run the engine to at least 2,500 RPM to heat up the O2 sensor.
You should get a reading that swings from less than 400 millivolts DC to
greater than 550 millivolts DC at least 8 times in 10 seconds. If the lower
voltage reading is above 400 mv or the higher voltage reading is not at
least 550 mv then the O2 sensor is bad. If it doesn't swing back and forth
8 times in 10 seconds then the O2 sensor is bad.
--
Ray O
correct the return address punctuation to reply

"Ray O" <rokigawa@tristarassociatesDOT.com> wrote in message
news:b28ad$4344098e$44a4a10d$31361@msgid.meganewsservers.com...[color=blue]
>
> "Jeff Strickland" <crwlr@yahoo.com> wrote in message
> news:EtednZVDhN8un9nenZ2dnUVZ_s-dnZ2d@ez2.net...[color=green]
>>
>> "Ray O" <rokigawa@tristarassociatesDOT.com> wrote in message
>> news:a1383$4343f95b$44a4a10d$30238@msgid.meganewsservers.com...[color=darkred]
>>>
>>> <wenmang@yahoo.com> wrote in message
>>> news:1128519527.007601.125160@g14g2000cwa.googlegroups.com...
>>>> Hi, all:
>>>>
>>>> My 2000 Corolla's check was on, and sent to the dealer, here was the
>>>> diagnose:
>>>> Access ECU, Locate DTC P0420 for catalyst below efficiency
>>>> Diagnose catalytic oncverter internally worn
>>>> new catalytic converter and oxygen sensor installed $1530.78 plus tax
>>>> Recommendation:
>>>> Front motor mount worn $219.55
>>>>
>>>> Here are my questions?
>>>> 1. is "P0420" the diagnose code for the problem?
>>>
>>>
>>> When the check engine light comes on, the car's computer usually stores
>>> a trouble code. Code P0420 means that the catalyst sytem's efficiency
>>> for bank 1 is below the proper threshold. The Corolla has an in-line 4
>>> cylinder engine so there is no bank 2 (unlike an engbine with a "V" or
>>> horizontally opposed configuration). Basically it means that the system
>>> thinks that the catalytic converter is not working efficiently. The
>>> catalyst in a catlytic conver does not wear out but it can become coated
>>> with contaminants over time so that the catalyst can't work on the
>>> gasses passing over it.
>>>[/color]
>>
>> Ray,
>> Can you discuss for the OP, the Upstream and Downstream O2 Sensors, and
>> whether his car even has them? I don't know if he has the down stream
>> sensor, and my inclination is to replace the O2 Sensor that is on the
>> exhaust manifold, which is the upstream sensor.
>>[/color]
>
> I described the "upstream" and "downstream" O2 sensors in my reply to the
> OP. I don't like the terms "upstream" and "downstream" because you will
> not find those terms used in a repair manual, just like I cringe when
> people call wheels "rims." Look in an auto repair manual and see if there
> is a procedure for mounting rims or balancing rims.
>
> I believe that most, if not all, OBD II vehicles have 2 O2 sensors. O2
> Sensor #1 provides feedback for fuel mixture and sensor #2 measures
> catylitic converter efficiency.
>[/color]

And Bank 1 or Bank 2 would refer to a dual exhaust system, where I assume
Bank 1 would be the left side, and Bank 2 the right? If the two banks came
together to a single exhaust from the CAT back, then there would not be a
Bank 2 "downstream" sensor. Sensor 1 is the upstream sensor, and Sensor 2 is
the downstream, where up and down are before or after the CAT.

Sensor 1 plays a role in manipulating the fuel mixture to achieve a
particular result, and Sensor 2 merely reports if the CAT is working. I
think I have that right.



[color=blue][color=green]
>> I agree completely with your advice here, but I'm a bit confused by the
>> particular code he got. My gut instinct is that this would be a
>> downstream O2 Sensor, but I don't know that his car has this or not.
>> Since he has the code, I have to assume he has the parts. I was going to
>> tell him to replace the O2 Sensor(s) because, like you, I think the CAT
>> should be pretty much a lifetime item in most cases.
>>
>> This is one of those times when my shadetree expertise just doesn't cover
>> what's going on.
>>[/color]
>
> The cat is lifetime in theory. In realty, the catalyst gets coated with
> contaminants like soot or residue from burning oil, or contaminants in the
> fuel. Taking the car on a highway for a good blowout every so often gets
> the cat good and hot and helps clear the pipes, so to speak.
>
> An O2 sensor has a much smaller surface area than the catalyst bed so it
> probably doesn't take as much to clog it's "nose."[/color]

My limited experience with O2 Sensors is that they simply cook. They live in
a VERY hostile environment, and cooking is a very real issue for them.
Especially the upstream sensors, I had one that crumbled and fell apart.

Given that the CAT is a lifetime part, then it makes sense to replace the
sensors before buying a new CAT. Sure, the CAT can go bad given enough time,
or a bad load of gas, but that really isn't something that happens with any
regularity until the car becomes advanced in years. I had an '89 Ford
chassis motorhome, and the CAT is fine after more than 15 years, so my guess
is that the OP's CAT is still serviceable.