Thanks Ray. Dealer charges 3 times than the local shop and for my 2000
Corolla with 157K on it, it may not be worth to pay that much other
than buying a new one.
I will cancel the code first, it comes back again, I'll send it to
dealer for diagnosis.
I personally prefer dealership service departments to avoid the very[color=blue]
> predicament you are facing. Toyota requires dealerships to have certain
> equipment, among them an exhaust gas analyzer, their technicians are
> factory-trained, and the warranty is backed up by the most financially
> secure car company in the world.
>
> The logic of how the ECM sets Diagnostic Trouble Code (DTC) P0420 is such
> that the most likely cause is a bad catalytic converter. #1 and #2 O2
> sensors work the same way and detect the presence of oxygen (O2) in the
> exhaust.
>
> Sensor #1 is sniffing the exhaust gas before it passes through the cat, and
> with the injectors sending fuel in pulses, the amount of O2 in the exhaust
> gas varies, so the voltage signal from Sensor #1 varies up and down.
>
> Sensor #2 sniffs the exhaust gas after it has passed through the cat, and
> the cat is supposed to clean up the gas. If the cat is working, the the
> voltage signal from sensor #2 should be much more even than the signal from
> sensor #1. If the signal from sensor #2 is varying and looks the same as
> the signal from sensor #1, then the cat has not changed the exhaust and the
> ECM sets DTC P0420.
>
> Other possible causes of P0420 are a damaged exhaust manifold or exhaust
> pipe (you would probably hear an exhaust leak), engine coolant temperature
> sensor not working properly, retarded spark timing, or bad O2 sensor.
>
> At this point, your best bet is to have a dealership diagnose the condition
> and with a written diagnosis, go back to the shop that did the work if
> something they replaced is bad.
> --
>
> Ray O
> (correct punctuation to reply)
>
>
>
>
>[color=green]
> > On Oct 12, 12:39 am, "Ray O" <rokigawaATtristarassociatesDOTcom>
> > wrote:[color=darkred]
> >> <wenm...@yahoo.com> wrote in
> >> messagenews:1160609005.854927.323010@m7g2000cwm.googlegroups.com...[/color][/color]
>[color=green][color=darkred]
> >> > Thanks Ray. I live in PA and I don't think that any place in US sells
> >> > leaded fuel
> >> > and I see no smoke coming out of exhaust pipe. The place where I have
> >> > CAT
> >> > replaced doesn't have scan tool. So I may have to send my car to other
> >> > place for the
> >> > scan in order to make sure that O2 sensors are good before exaust shop
> >> > can carry
> >> > out warranty otherwise, they probably won't do anything.No regular gas
> >> > stations sell leaded fuel, and
AFAIK, leaded fuel is not
> >> available in the U.S., but I like to cover all bases when I think of it
> >> ;-)[/color][/color]
>[color=green][color=darkred]
> >> No smoke out of the tail pipe is good![/color][/color]
>[color=green][color=darkred]
> >> If the place that replaced the cat does not have a scan tool, then how
> >> did
> >> you get the code? If you have a personal scan tool, perhaps the shop
> >> that
> >> replaced the can use it to check the codes. You can chcek O2 sensor
> >> operation with a volt meter.[/color][/color]
>[color=green][color=darkred]
> >> If the cat is aftermarket, I'd bet that the replacement cat is bad.[/color][/color]
>[color=green][color=darkred]
> >> Good luck!
> >> --[/color][/color]
>[color=green][color=darkred]
> >> Ray O
> >> (correct punctuation to reply)[/color][/color]
>[color=green][color=darkred]
> >> > On Oct 11, 6:55 pm, "Ray O" <rokigawaATtristarassociatesDOTcom> wrote:
> >> >> <wenm...@yahoo.com> wrote in
> >> >> messagenews:1160599775.545655.124910@k70g2000cwa.googlegroups.com...[/color][/color]
>[color=green][color=darkred]
> >> >> > Hi,[/color][/color]
>[color=green][color=darkred]
> >> >> > It is raining today, on my way home, the check light turned on and I
> >> >> > checked, it reads P0420. I just have CAT and 2 O2 sensors(front adn
> >> >> > back) replaced about a month, how come? what possibly went wrong?
> >> >> > What
> >> >> > should I do next?My guess would be that the replacement catalytic
> >> >> > converter is defective or
> >> >> something is contaminating the catalyst.[/color][/color]
>[color=green][color=darkred]
> >> >> Leaded fuel or huge amounts of engine oil leaking into the combustion
> >> >> chamber (with accompanying blue-gray clouds out the exhaust) could
> >> >> contaminate the catalyst, but if you don't see the blue-gray smoke and
> >> >> you
> >> >> haven't used leaded fuel, then a defective catalytic converter is
> >> >> likely.[/color][/color]
>[color=green][color=darkred]
> >> >> I would bring the car back to the place that installed the cat and
> >> >> sensors
> >> >> for a warranty repair.[/color][/color]
>[color=green][color=darkred]
> >> >> Good luck!
> >> >> --[/color][/color]
>[color=green][color=darkred]
> >> >> Ray O
> >> >> (correct punctuation to reply)- Hide quoted text -- Show quoted text -- Hide quoted text -- Show quoted text -[/color][/color][/color]
