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Overfilled oil

I overfilled my toyota matrix with probably 3+ quarts of oil, drove it about 3/4 mile. It smoked badly. I remedied this and now the check engine light is on indicating a problem with the O2 sensors. I replaced the O2 sensors but the light came back on. After about 1000 miles I then replaced the Cat. The light eventually came back on. Should I try and replace the sensors again? I was thinking maybe they got soiled while they were running in the old Cat?

You messed up an oil change a year ago , maybe you should have it done. You also had sensor problems.

Did you use the OEM sensors and cat? That could make a difference as well. What is the code related to the check engine light?

I would have tried driving this some first before replacing everything. Often crud like this will burn out of the system and you will be fine for a while even though you will have likely shortened the life of the emissions controls in question.

Did you clear the codes before replacing all this stuff? The code will usually stay even after the problem has been corrected until it is cleared. I always clear a code at least once before taking it too seriously. You probably had all kinds of strange readings from all that oil getting burned and this may have been largely corrected by draining out the excess and running the car normally for a while.

I don’t believe I used OEM parts. I did clear the codes but the light keeps coming back on. I’ve driven it about 10,000 miles since I did this but it hasn’t helped. Should I just try toyota factory O2 sensors?

The sensor is working just fine, it’s telling you there is a problem, you need to find out what the problem is.

Any suggestions how I should go about doing this?

I have a suggestion. Take the car to a MECHANIC.

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Toyota doesn’t make O2 sensors or catalytic converters. They purchase them from a vendor/supplier.

So forget getting so called OEM parts.

Here’s what I would try.


By OEM parts, I mean the brand that Toyota installed from the factory.

I had a car that came with a Denso O2 sensor. I replaced it with a Bosch and that one cost quite a bit more. I thought I was buying a premium brand and that I was making the right decision. I didn’t get a check engine light but the car seemed to have a lot of hesitation and stumbled on acceleration after I installed that new sensor. It would also sometimes buck and kick like someone who didn’t know how to drive a manual transmission.

I posted about my woes on a forum dedicated to that car. I mentioned that I had replaced the O2 sensor with a premium Bosch unit and someone posted that I should have used the Denso sensor. Anyway, that Denso cost about 1/4 of the Bosch so I went out and bought one. My problems went away. Apparently the ECU is tuned to the Denso. Maybe the same is true with your car. Figure out what Toyota installed from the factory and do the same.

I agree that running a good fuel system cleaner through this might not be a bad idea. I also agree that taking it to a mechanic might also not be a bad idea.

I am curious as to WHAT CODES are coming up on the check engine light. Do they correlate to the O2 sensors or cat? What if something else went wrong coincidentally and you thought it was an emissions component while it isn’t? Also, maybe something gunked up the EGR and this is an EGR code and you are attacking the wrong problem. Again, it might be cheaper to hire a mechanic than just throw money at this thing.

Hmmm. You can’t even change the oil without screwing things up, you throw parts (waste money) at a problem you obviously can’t diagnose. Yet I’m the @$$hole, for suggesting you take it to some one competent to diagnose the problem? Please don’t let the door hit you.


What is the code you keep clearing ?
And O2 bad is not what we need, we need the p0000 number(s)

Thank you so much for your help! The code is PO420.

OK, that is a catalytic converter efficiency code. Do you have a V6 or is this a 4 cylinder? If a 4 cylinder, you probably only have one cat. Some of the aftermarkets may not be up to snuff.

This probably won’t cause you any fuel economy, driveability issues, or cause you further damage but will cause the car to fail an emissions inspection. You could have purchased a cheap aftermarket catalytic converter that isn’t up to the job or the downstream O2 sensor isn’t up to the job either.

Remember that a “check engine light” doesn’t mean a whole lot without the code(s). That P0420 definitely narrows it down to an emissions systems problem and not some other coincidental issue.