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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I mean check light was on
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.

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.

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.

Yes.
--
Ray O
correct the return address punctuation to reply
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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

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
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

lower
forth
This is a good procedure for the O2 sensor before the catalytic converter, but won't work for the sensor after the catalytic converter, if the converter is working. The output from the sensor after the converter varies much less since, if the converter is working, there should be little or no unburned hydrocarbons left.
Ed
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You should know by now that the last couple of years, Toyota has NOT used a conventional "O2" sensor before the catalyst. After the catalyst, same ol O2 but the input is only used for catalyst performance tracking. The current technology employs an exhaust sensor that operates on a different principle and is called an Air/Fuel ratio sensor. They are NOT interchangeable.
--

- Philip



Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
That is most likely what is going on. The sensor is failing -- or has failed -- and is sending a false report. There's a chance that the CAT is toast, but if I was doing the job on my own car, I'd replace the sensor before I did anything.
I'd actually reset the Check light, then wait to see if it comes on again. If it does, AND it has the same code P0420, then I'd replace the sensor, reset the code, and wait again.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
How to reset check light? I don't have tool to check the DTC. The code was checked/given by the dealer. I may need a tool, and what is it called for checking DTC?
Thanks
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Your car is compliant to On Board Diagnostics, Level 2 (OBD II), and you can do a search on the Web to learn more.
AutoZone (an auto parts store) will let you use the coed reader for free. The reader will reset the codes. There are readers on eBay that cost in the range of about $60 to about $150. There are four models from the same maker that have varying features and abilities, my suggestion is that the tool costing in the mid range is the one tha tmost of us ShadeTree mechanics will need. If you have an AutoZone store nearby, and don't want to buy another tool that won't get much use, then go to the corner and use theirs for free.
When you search the 'net for "OBD II" yo will find more than you ever wanted to know. Do the same search on eBay, and you'll uncover lots of sources for the tool. AutoZone has them for sale, or you can use theirs for free. If you want to use it in the parking lot, then you just leave your driver license as a security device. If you want to take the tool home, then they will ring it up on a credit card, then give a Full Refund when you bring the tool back. I've used the tool both ways, in the parking lot and at home.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I'm in California, and they are expressly prohibited from checking my car for me, but they can let me use the tool to check it myself. If they will check the car for you, then even better because this takes away at least one level of difficulty.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You can go to most auto parts stores and borrow one for free. The scan tool is an OBD-2 scan tool. Just read the instructions with the tool.
--
Ray O
correct the return address punctuation to reply
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Possible but highly unlikely in a short period of time (under a mnth).
--
Ray O
correct the return address punctuation to reply
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.