Check Engine Light in 2002 Corolla Automatic

[Tom Z]

Hi all,

New member here, looks like a great forum.

I have a 2002 Corolla whose CEL keeps on coming back on. I am mostly a GM guy, so my scanner will not work for the Toyota. I have a basic one that gives me the code. Tried both O2 sensors, cleared the codes, and they've both come back.

Code number is PO420, message "Catalyst below threshold value." Light comes on after three trips (once code is cleared).

Seems to run well. No noticeable misfire. Did a power purge on the injectors -- no luck.

Any ideas are welcome.

[rgurleyjr]

It's either the rear 02 sensor bad or your converter on it's way out, I had the same code. There's a thread on here from a guy on a Celica forum that posted a way to wire in a resistor to trick the sensor. I ended up doing that and now no more P0420. I ended up removing my converter anyways and looked to see if it was indeed bad and it was as clean as you can get, so the sensor was my problem.

[wylee]

My Prizm had the same code when I bought it. I got it from a private sale so I knew the car burned a little (yeah right!; the seller wasn't completely honest there) oil and had a coil replaced do to a missfire about 30K miles before I bought it. The car was driven awhile with a misfire, it is a known oil burner, and add the P0420 code...I ordered a cat and a rear oxygen sensor from Amazon and my check engine light problem was resolved...after inventing some new cuss words. ~;-)

[Quickness]

Im having the same problem with mine and i was told that it was the sensor. i called some shops and the price for an 02 sensor is about $115.

[rgurleyjr]

http://www.newcelica.org/forums/showthread.php?t=216641

$5 in parts and they had them in stock. Only problem is that you have to pull your passenger seat out to access the plug. I did it, it works.