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Joined: Nov 2002
Posts: 489
CRBN BLU
Senior Member
CRBN BLU Mar 27, 1:33am - #426430 

Senior Member
2002 Toyota Celica GT

Joined: Nov 2002
Posts: 489
Hampton, VA
Code P0420 - What to do?

Ok, so I'm driving down interstate and my CEL comes on. Not the first time in the past month. But I did stop this time to get it checked.

Code P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
-Gas leakage on exhaust system
-Open or short in heated oxygen sensor circuit
-Heated oxygen sensor
-Three-way catalytic converter

My car only has 63,xxx miles on it. The AutoZone guy suggested the O2 sensor. Any one else get this code? What can be done to test the different aspects of the possibilities and how can I fix it?

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Joined: Dec 2004
Posts: 15
Shadow_GTS
Member
Shadow_GTS Mar 27, 6:50am - #426431 
Member

Joined: Dec 2004
Posts: 15
Rochester, NY
I had the same code after i installed my TRD exhaust. One of your o2 sensors needs to be replaced or it has caused a minor leak around that vacinity. My problem was that my brother stripped my o2 sensors threads and it was leaking air at that port throwing that very same code. Luckily he is a engineer and borrowed a tool and die kit from work and retapped it. No problems since.
Joined: Dec 2004
Posts: 401
maingear
Senior Member
maingear Mar 27, 8:34am - #426432 

Senior Member
2002 Toyota Celica

Joined: Dec 2004
Posts: 401
Arkansas
Get a scanner that can read the O2 values while the engine runs. Let the engine temp rise and check the voltage fron the O2 with the scanner. If there is voltage than you can scratch the short/open in the circuit.


If I'm not mistaken, Isn't the emission systom on this car covered under a 100,000 Mile warranty??? confused
Joined: Feb 2004
Posts: 965
morris
BerraquĆ­sima!
morris Mar 27, 9:23am - #426433 
2000 White Toyota Celica GT
BerraquĆ­sima!
2000 Toyota Celica GT

Joined: Feb 2004
Posts: 965
Orange County, CA
Originally Posted by morris
I got the same last october...
but my light comes and goes by itself... sometimes within a few miles, others, withing hundreds. I'll take my car for diagnosis (besides: brake recall, oil change- they're so nice a my toyota dealer- and other minor maintenance... ) and see what happend... I think the problem is the O sensor...

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Joined: Jun 2004
Posts: 1,696
Polykarb
Metal Storm 2040
Polykarb Mar 28, 1:38am - #426434 

Metal Storm 2040
2000 Toyota Celica

Joined: Jun 2004
Posts: 1,696
Tampa, Florida
yeah i've been running my GTS with cel on for like a month now with 6 thrown codes as well as the one mentioned in this thread. confused confused

FF TWINCAM BEAUTY: CELICA
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