Was coming to a stop, and my check engine light came on. I didn't notice anything really wrong. Car was running fine.

I took it to autozone and they gave me the P0420 Error

Catalyst Efficiency Low - Bank 1
The oxygen sensors monitor the catalytic converters ability to store oxygen

Causes
#1 Catalytic Converter Defective (Failure possibly due to #2, #3, or #4)
#2 Engine Misfire or Running Condition
#3 Large Vacuum Leak
#4 Engine Oil Leakage Into Exhaust - Valve Guide Seals, Piston Rings

Anyone have this? Suggestions? Things I can easily check for without having to take it to a mechanic? And will it be OK to drive for the next few days? I drive it to work, 37 miles one way.

I didn't notice the engine running rough at all. Running just as fine as it always has.

Don't hear any vacuum leaks. I do have an exhaust leak you can hear at roughly 4,000rpms+. That is near the back, before the muffler.

I just replaced the valve cover gasket about 10k miles ago. It was leaking. I still have a small oil leak on the CPS gasket. Will replace soon.

But other then that, no real white smoke or burning of oil I can see in the exhaust. So very confused.

I tried resetting the computer by disconnecting the battery, but it never went off. I thought it would at least go off, and if there was still a problem come back on aftera few. But it appeared to never even go off. So I am going to have to take it in to reset. I need to get it reset so I can see if it was just a one time mishap? Or its a continued problem.

Any ideas to reset besides mine?

Could it really be just a bad CAT? OS2 sensor? Or I am going to guess that would have its own code...

Anything would be helpful! Thanks!!

1998 Dodge Avenger
121k Miles
2.0L
5spd
Very well maintained. I take care of it very well as far as maintanance.

- Kevin

 

The computer measures the efficiency of the catalytic converter by looking at the rear o2 sensor. Most likely the sensor is bad and that is what is causing the code to come up. You will be able to drive with this code without any ill effects.

I would try getting it reset - or disconnect your battery for like 5 minutes and it should go away. There is a good chance it won't come back for a while. As the sensor continues to go bad it will come back more often

 

Well, like I said, I don't notice anything wrong with the car, or any white smoke, etc.

I tried disconnecting the NEG(-) of the battery for about 15 minutes. And when I hooked it back up, and started, the Check Engine light was still on. So maybe something else? Or maybe disconnecting the battery isn't working. I don't know.

I was hoping that it would either stay off, or come back on like a minute later to let me know if it was a 'still happening' problem. But, again, it never even went off when I started the car like normal. So, could it be more serious? Or just take it in to get it reset and see what happens?

 

If the converter were actually going bad and had become inefficient then it would take the computer 15 minutes or more of driving for it to figure that out.
I am going to say the sensor is reading way out of range and because of that it instantly throws the code.

 

yea i have that exact same code on my car... got a code reader 2 get more precise than the keydance reading
and it was the REAR SENSOR - NO ACTIVITY. so the sensor went bad.. erased the code and it just came back about a week later.

 

Well, bought a Aftermarken Bosch, Part 15730. It looks like the first O2 (before CAT). I called to verify, they gave me both part numbers and said the 15730 is for AFTER the CAT (2nd, under car, under drivers seat). I replaced, Check Engine Light is still on. Had to splice the cable and everything. Looks fine though, according to directions.

I disconnected the battery (NEG only) for 5 minutes and tried turning back on, error wont go away. So either its NOT resetting, or its a diff problem. I took the POS and NEG off battery and letting it sit a bit longer. Anyone know how to FOR SURE reset the computer? Or will I have to take it in? The Check Engine is coming on as soon as I start the car. Never is off. Any help here on reset? Or perhaps its a different problem... ?

Thanks!

- Kevin

PS: It came off very easily! Was suprised... hah. Here I thought I would have it out with a rusted O2 sensor *GRIN*... I heard horror stories but I'll be damned. Kroil and about 10 minutes of soaking, boom, came right out.

 

Well, disconnected POS and NEG this time, left it off for about 30 mins. It reset the computer. The Service Engine Light has yet to come back on. The part seems to have worked and all seems well.

Next Question would be to ask... if I never really 'reset' the error code. I have always tried the NEG on the battery only and last time I left it for about 15-30 mins or so. Came right back on.

This time I replaced the sensor, did the same thing with just the NEG and it came back on. So tried disconnecting the POS and NEG and it reset. And again, yet to come back on. So don't know if it really was that sensor or just a blip and I didn't really erase the error code earlier/previous day.

Either way, I have noticed a difference in driving, beleive it or not. Was shocked. More power, more sensitive? Thanks to all for the help. Looks like its fixed (For now)...

- Kevin