[bigpawn]

I purchased a 2001 corolla for my daughter. 150K
When the car was purchased it had p0420 light on, it needed a new converter.
The converter was replaced (aftermarket). The car runs great, it doesnt burn oil.
After 5 months the P0420 light came on again. I took it to the dealership and they
said it needed a converter. Cost $50.
I took the car back to the exhaust place that and re reaplaced the converter. He inspected the converter and it was clean. We both inspected it together.
He replaced it anyway, wasn't happy about it, but it was under warranty.
A month later the engine light came on again. it was a po420 code.
I took it back to the dealership and ask them if the rear o2 sensor was bad. They said it
wasn't. They said if the sensor was bad, it would give a different code.
They me told since it was an aftermarket converter that it wasnt up to toyota specs.
I was thinking about replacing the 02 sesnor anyway, but didn't want to spend the money on a sensor that wasnt bad.
Just need some simple advice. The dealership didn't seem to help at all. They want to replace the cat converter and they didn't even have one in stock.
Sincerely
cj

 

[prophase]

To be honest, don't do an o2 sensor unless you have to. It does however improve gas mileage and running of the car in general if old.

With regards to the converter, some brands are not the same quality as others. You get what you pay for.

$50 for a converter sounds way to cheap if you ask me.

 

[bigpawn]

$50 dollars was for an inspection to tell me the converter was bad. This was after it was replaced the first time.
It cost 200 to replace the converter the first time. The second time the exhaust people replaced it for free.
I did not have the dealership put on a converter, it was going to cost about $1200.

cj

 

[prophase]

$50 dollars was for an inspection to tell me the converter was bad. This was after it was replaced the first time.
It cost 200 to replace the converter the first time. The second time the exhaust people replaced it for free.
I did not have the dealership put on a converter, it was going to cost about $1200.

cj

Whoops, my bad! To be honest, I never heard of a dealer charging that much for a converter with installation. Sounds way way to high!

 

[bigpawn]

Yes, the dealerships wants that much for the converter.
I really dont think we need to debate the cost for a converter from the dealership.

Well, could the aftermarket converter set the o2 sensor off?
Could the sensor be faulty?

Has anyone else had problems with aftermarket converters setting off the O2 sensors?

Just looking for some advice.

 

[demonfire]

The second sensor that throws the P0420 code ONLY reads catalyst efficiency. Replacing that sensor should be in the ballpark of $60-$120 (i'm not that familiar with toyota sensors), but then again if it works okay when the cat is new, and then after a few months goes off, sounds like whatever catalyst the unit you're running burns up rather quick. Just because a cat "looks clean" doesn't mean it is still functioning. The built in oxygen may be used up too quick, etc. Hard to tell, and actually my wife's 2003 corolla has the same code and i am trying to price out new cats.

 

[prophase]

I gave my mechanic friend a call.

He advises that most likely the o2 sensor was bad first. A bad o2 sensor can cause the cat converter to go bad over time.

When you replaced the cat converter the o2 sensor was already bad.

He advised in most cases, an o2 sensor should always be replaced with a cat converter to avoid the problem you are now having.

I have known him for about 15 years. He's top notch in my area.

He advised that a bad cat converter should not trigger an o2 code unless the o2 was already bad.

 

[Guest]

a bad cat can make a 02 sensor go bad if the cat was bad long enough in the first place, so making two problems from one. very well could be a bad 02 sensor, but if the mechanic tested the 02 sensor and said it wasnt the problem i wouldnt replace it. to be sure i would replace sensor and cat at same time to eliminate those possibilities. Could be a short in your wiring somehwere, but I doubt it.

 

[bigpawn]

the O2 sensor was not actually tested by toyota.
I did ask if it was bad and they said if it was it would
give a particular code ( i dont remember which).
So we left it at that.

I read a post on how to test the sensor.
I will try that and if that's it, I will replace the sensor.

thanks for the info.

I will cost about 100-175 to replace the sensor. I willing to
pay that if it will fix the problem.
cj

 

[prophase]

the O2 sensor was not actually tested by toyota.
I did ask if it was bad and they said if it was it would
give a particular code ( i dont remember which).
So we left it at that.

I read a post on how to test the sensor.
I will try that and if that's it, I will replace the sensor.

thanks for the info.

I will cost about 100-175 to replace the sensor. I willing to
pay that if it will fix the problem.
cj

Replacing an o2 sensor that is old but still working will still yeild a better running engine and better gas mileage, they get real crappy over time.