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Ron Z.
Ron Z., - Chevy Tech -
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Experience:  18+yrs experience. State Inspector and Chevy Diagnostics
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2002 Chevy Cavalier: a Check-Engine light on..Catalytic converter

Resolved Question:

Writing about our 2002 Chevy Cavalier that has NOT been hassle-free. The latest is a Check-Engine light on. AutoZone use their troubleshooting meter and it produced the following info:

Definition: Catalyst Efficiency low-bank 1
Explaination: The oxygen sensors monitor the Catalystic Converters abilty to store oxygen
Probable Cause: Catalytic converter defective (failure possibly due to #2, 3, or 4), Engine misfire or running condition, large vacuum leak, Engine oil leakage into Exhaust-valve guide seals, piston rings.

Most recent repair on this car was early March. Included remove/replace A/C pressure sensor & harness and an oil change (nearly $500!). No idea if there is any connection to this, but thought I'd mention. We also had a tune-up done in NOvember 2010.
Cooincidentally, just today, I had the Oxygen Sensor changed on our 2001 Subaru Forester. We never get a break with these 2 cars lately!

Could you please point me in the right direction?

Newport, RI
Submitted: 6 years ago.
Category: Chevy
Expert:  Ron Z. replied 6 years ago.

Welcome to! My name is DriveFast71(Ron) and I will do my best to answer all of your questions completely and accurately.


The Catalyst Efficiency low-bank 1 (P0420) is a fairly straight forward code, and as staed above- the oxygen sensor monitor the exhaust oing into, then out of the converter. When they see the converter is not "cleaning" the exhaust the way it should, the engine light is set, and the converter is deemed to be faulty. Unfortunately- you are going to need to replace the converter. Keep in mind, those "universal" or "cheap" converters they sell at aftermarket parts stores do NOT meet OE standards and will not solve the problem. You will need to get a "good quality" converter (i've had fairly good luck on GM with the "Walker" brand).


Ron Z. and 2 other Chevy Specialists are ready to help you
Customer: replied 6 years ago.

Thanks for your swift and clear reply.

I do have a follow up question for your. Am I able to buy a quality replacement converter, such as what you recommend above via an outfit like AutoZone, or must I rely on an "official" dealer/repair shop to buy/replace? Every time we drive into the Chevy dealer/service place it seems to cost $500. Today, I had a local body shop replace my Subaru's oxygen sensor with a quality Bosch product and simply paid them $60/hour. Can I do the same for this Chevy (i.e. find a quality part at Autozone and have the body shop handle, OR is this a "big job" requiring the services and access-to-official parts that only the dealer can do?


Expert:  Ron Z. replied 6 years ago.

I would suggest staying away from AutoZone, as the converters they have in stock aren't the best quality. However, NAPA will have good quality converters readily available in stock. No need to have the Dealer do this. Any local shop can take care of this repair with no issues. It simply bolts into the exhaust system. It should take around 45min to and hour to complete the job.

Customer: replied 6 years ago.

Thanks for your suggestion to steer clear of Auto Zone for this part.


I did go to the Napa website, as we have a store nearby. There was a myriad of Catalytic Converters for our make/model/year (2002 Chevy Cavalier/2.2L L4 MPI OHV 8V), with a LARGE variation in retail price. Frankly, I don't want to pay more than I have to and it's hard to know which is THE ONE to go with. Here is a link to the Napa webpage showing the parts:


Can you suggest a particular part, or should I ask Napa what they suggest?

Also, how long is it "safe" to drive with this check engine light on (repair NOT made)?

If I can push it off until first week of May I would prefer to do that, but this car is currently being driven 60 miles/day, round-trip to work (my husband's). If this is a problem we could trade cars, I guess.

Thank you! Ann

Expert:  Ron Z. replied 6 years ago.

The link above you provided, came up as "page not found for me" (i don't know why). NAPA has great, knowledgeable employees- so simply telling them you need a better quality converter should do it. Like I say previously- I've had good success with "Walker" brand. And if the converter hints to "Universal" - stay away. A "good" converter is going to run in the neighborhood of $500.


As for how long you can safely drive the vehicle- as long as you are not experiencing any drivability issues like lack of power or stalling, it should be ok. Keep in mind the converter's internal make-up can deteriorate quickly. This usually leads to exhaust clogging and will present as a lack of power symptom. If this happens, try not to drive to far or too long as this will create other engine problems.


Ron Z. and 2 other Chevy Specialists are ready to help you
Customer: replied 6 years ago.

Hi Again,

I just paid another $18 as I have an additional question, to follow up on the above discussion. My husband left his headlights on over night, resulting in a dead battery (he took my car to work and left me with the problem...). Anyway, AAA just finished jumping the car and it's still running in the driveway for a few more minutes. Since I have his car for the day, I figured I'd deal with the Catalytic Converter problem and run over to Nappa to buy the part and then have it installed. HOWEVER, I was surprised to notice that the "Check" engine light is no longer on?! So I'm confused as to whether it's related to the temporarily dead battery, or what. Your thoughts?


Expert:  Ron Z. replied 6 years ago.
Ok- the reason the Engine light is Off, is becasue the battery "died". When the battery looses all power OR you remove the "NEG" cable for 15 minutes or more, this "re-boots" the vehicle's on-board computer (very similar to when you first turn on your home computer- it takes a few minutes to get to your desktop. Same idea). The on-board computer will now do a system-wide re-check, and re-assess any problems. The light WILL return within 50-75 miles of normal driving.
Customer: replied 6 years ago.

Thanks for confirming my suspicion. Clearly, the repair still needs to be made. You've saved me a "dicussion" with my husband, who would possibly insist that the problem has "gone away". I wish!

BTW, what is an "NEG" cable? And how can I self-identify if this car is a single- or dual-cam engine? This will determine which of the 2 Walker brand C.C.s I need to buy.

Expert:  Ron Z. replied 6 years ago.

The "NEG" cable is the black cable going to your battery (there is red (positive) and black (negative)). "Removing the NEG cable" is jsut another method of "code clearing" - which SHOULD be done for you after the repair is made.


To identify your engine, I will need the 8th digit of your VIN#


Customer: replied 6 years ago.

Here is our Vin # XXXXX its entirety. There were spaces between the sets of digits, so I didn't want to mis-identify the 8th digit:


1 G1 JC524327322725


I had this info. with me when I first went to Napa, driving my Forester, to inquire about Catyletic Converter parts for the Cavalier. The guy behind the counter said he'd have to look at the Cavalier's engine to identify dual vs. single cam, and when I asked him if he could figure it out from the VIN # XXXXX other paperwork I had with me, he said "No". He seemed annoyed and impatient when I asked questions about the various CC part options (no, there was not a line behind me). While they may not have as high quality parts, I've never been treated rudely by the AutoZone staff.

Perhaps this guy was just having a bad morning (he did seem a little hung over!).


Expert:  Ron Z. replied 6 years ago.

Wow! That's odd. Sorry to hear. I do a TON of business with NAPA. Probably an "off" day.


At any rate, yes, with the VIN# XXXXX can tell the engine size. The 8th digit here is a "4" (don't count spaces) which means you have the 2.2L - SINGLE overhead cam.



Customer: replied 6 years ago.


For whatever reason, the SINGLE cam C.C. price (Walker) is more expensive than the DUAL cam ($366.49 + tax vs. $303.49+ tax) , so I was crossing my fingers for a dual.

WIsh me luck with "Mr. Charm" over at Napa!

FInally, since I already paid an additional $18 this mornign BEFORE writing the question, I don't think I can click "Accept Answer" or I'll be charged again.

Expert:  Ron Z. replied 6 years ago.

No worries. It's all good. We're even. Glad I could help! Good luck with Mr. Charm! hahahaha!


Customer: replied 6 years ago.

After all that, Napa did NOT have the part in stock. They offered to order in, of course, but I had time lined up to have it installed, so I phoned AutoZone, which is right down the street. They too had to order it, but had the identical Walker part and for $77 LESS -- go figure!?

Thought you'd find this of interest. Anyway, the work if finally done on the C.C.. Thanks for your input.

Expert:  Ron Z. replied 6 years ago.
Excellent! Glad to hear!

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