Engine 03 Corolla Check Engine Light On

well i got the 420 code also for my 2001 ce. the shop said it was my cat. so i got a new cat installed. i need to give it some time and a few gas tanks (maybe 3 fillups) to gaurantee i don't have a bad o2 senor. i can keep you posted. there can be several factors involved depending if it's your o2 sensors.

did you recently hit the cat over a bump?
are you getting bad gas mileage?
any exhaust leaks from your pre-cat sensor?
have you been using octane boost?
have you been using fuel additives such as zmax or slick50 etc...
what is your oil level? make sure you're not over filling your oil reservoir.

try out a CEL bypass

go to my thread:
http://www.vvti.net/forums/showthread.php?t=12682

03 Corolla Check Engine Light On

I've Got A 03 Corolla ,and My C.e.l. Came On . I Got Autozone To Pull The Code Which Was Po420. It Shows To Be A Cat. Related Problem In My Repair Manual , But Could It Be One Of My O2 Sensors ? And Which One Can It Be? WHICH ONE IS BANK 1 OR BANK 2 ? THE LINK BELOW IS A FULL LIST OF CODES THAT I HAVE FOUND .


http://www.toyotanation.com/forum/t148676.html

Since Corolla's are only 4 cyl they only have one bank. There is however bank 1 sensor 1 and bank 1 sensor 2. Sensor 1 is before the cat and sensor 2 is obviously after. Just give me you VIN. The ECM will need to be recalibrated and the entire catalytic converter assembly will need to be replaced. If you are under 96 months or 80,000 miles it will be warrenty. I won't know if you qualify until you give my your VIN however.

SAme issue... I got an 02 sensor simulator... google it.

I Took It To The Dealership And Found Out It Was A Bad Cat. Since It Was Under The Federal Emmissions Law ,8 Years Or 80,000 Miles WARRANTY , It Was Repaced Free Of Charge .

Glad you got it taken care of. I knew it would be covered.