SolaraGuy.com

Searched around, mostly dead end threads with no follow up. Long story short, 2002, 2.4, 140k mileage. Cruising up the parkway this morning and the CEL comes on. Went to Autozone after work and tbey scanned it with a P0420 code. Looking for possible fixes and or possible parts needed. From what Ive read it could be a bad catalytic. Converter or front O2 sensor. Thoughts?

P0420 – Catalyst System Efficiency Below Threshold (4-Cylinder engine)
· Three-way catalytic converter malfunction
· Open or short in heated oxygen sensor circuit (bank 1, sensor 2)
· Heated oxygen sensor malfunction (bank 1, sensor 2)
· Open or short in heated oxygen sensor circuit (bank 1, sensor 1) or A/F sensor 2 circuit


Hopefully it's an easy fix!

So what does that mean lol, that looks like the printout Autozone gave me. It even said on the slip that its most likely a leak before the cat.

it means that one of your oxygen sensors are detecting to much fuel or air going through the cat. could mean your cat is bad, or if its the upstream sensor your car could be running rich or lean. best thing to do is bring it to shop and let them look at the freeze frame data. that will tell them exactly what was going on when the CEL went on.

most people think that changing the sensor will solve the problem, but its usually a waste of money. if it is the front O2 sensor then the cat probably isnt the problem because its upstream from it and reading the exhaust coming directly from the engine.

bottom line is go to a shop and get some diagnostic work done. that should't cost you more than $60, hell some places will do diag work for free. hope this helps a little.

Since we are on the subject, I have a 2001 2.2L and recently had the catalytic converter replaced. Shortly after installation my CEL came on and the code that was spit out was the P0420. Does anyone know why/ or what caused this? Thanks.

Apparently I didn't double check the gas cap like I always do. CEL came on Tuesday, refilled Friday afternoon, drove the 50 mile round trip to work with it on. Parked overnight, went for a 25 mile drive Saturday, CEL went off that night. Hasn't come back on.

Lol

I always double check, I live in Jersey so I dont pump my own gas and if I run into the store or something I don't know if the attendants clicked it enough. They apparently didnt. Oh well.

And two weeks later its back on...

Regardless of what everyone says, theres a good chance it's the o2 sensor. Just be sure when it is changed, have your mechanic reset the computer. A few of the guys at Advance Auto here where I live do it because I've been in there a ton of times. At 221+K miles, I've replaced 2 in my wifes Solara, and after both changes the CEL light would stay on until the computer was reset. My wife drives 60 miles round trip to work and back so it's not always a matter of driving it a few miles to get the light to go off. I did replace the CC one time but it was because I needed a new flex joint pipe and it all comes as one piece. That wasn't a CEL issue though.

It went back off later that night. How difficult is it to replace the 02 sensors on a 4cyl 2002? whats the cost?

My 03 did the same thing a few years back with the PO420 code. I replaced both 02 sensors (cost like 150$ for both of them ?) and the problem still wouldn't go away. Ended up being the catalytic converter which is part of the exhaust manifolds needed replacing.

I guess its less expensive to start by replacing the sensors, but be prepared for having to replace the cat.

edit... after i replaced the o2 sensors, I would reset the codes and it would not show the code of anywhere from a few days to weeks of normal driving. in the end I did an anti foul mod, and the prob is gone now.

I have read the the 2az has issues with the ecu throwing a code for bad cat way too easily. I think its a service recall for some models?

Its been a few years but thats the best I remember. Hope that helps!