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2000 Toyota Avalon Check engine light code P0420

Tiny
NJAVALONGUY
  • MEMBER
  • 2000 TOYOTA AVALON
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 85,000 MILES
Hi,

I had the check engine light come on in my 2000 Toyota Avalon XLS (85000 miles) and I took the car to autozone and my local mechanice both of whom diagnosed the error code as P0420 - Catalyst System Efficiency Below Threshold ( Bank # 1). My mechanic said this problem was common on avalons and attributed the reason to the catalytic converter failure. He said it would cost me $ 630 /- for parts + $ 100 /- for labour to replace. Which In my opinion is too high. Has anyone faced a similar issue before? There is no effect on the performance or MPG of the car. What could've gone wrong and how much will it cost me to fix?
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Thursday, March 6th, 2008 AT 8:33 PM

14 Replies

Tiny
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  • MECHANIC
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Your mechanic is right and the price sounds a bout right. IT's about two car payments. The avalon is a good car and you'll get your money back in the long run.
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Thursday, March 6th, 2008 AT 8:37 PM
Tiny
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I have tried looking for the prices of a cat converter for a 2000 Avalon on the net and I found prices in the range of $ 230 odd. My mechanic got the quote from a toyota dealer. And I am unable to understand the mor than double difference in price. Is there a cheaper option like sourcing one from a parts car from a junkyard which would help? What are the lon term effects of driving the car with problem?
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Friday, March 7th, 2008 AT 8:20 AM
Tiny
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Your going to want to use the OEM on this one, aftermarket ones have been problematic.

Junkyards cannot legally sell converters.

I'm not sure what consequences will come of not replacing it. It will likely. Make for a more expensive trouble shoot if this problem exists and another one begins.
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Friday, March 7th, 2008 AT 10:46 AM
Tiny
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Thanks Service Writer for those quick replies. However, can you pls tell me the exact part number ( or provide me some source from where I can get it) of the cat converter which will have to be replaced. I call up Toyota parts center and am thoroughly confused since they have quoted my prices ranging from $ 880, 610 to 250 for various cats. Any help in this matter would be much appreciated !
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Saturday, March 8th, 2008 AT 8:27 AM
Tiny
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Toyota parts are a pita. What you have to do is give them your VIN to get the part and or part number. I'm not sure about your situation, but you may be best to let your mechanic handle that. Couple reasons. One, if you run into a warranty problem, it will become your problem and that can be a hassle. Two, the shop will get the part for about 10% or so less than you and a shop needs to make a part profit to stay in business.

You can try toyota national hotline if you can't get what you need.
1- 800-331-4331
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Saturday, March 8th, 2008 AT 12:52 PM
Tiny
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Thank You Service Writer. For the patience to answer all my questions. Today the check engine light has automatically turned itself off ( after I changed the gas station and drove for 110 miles since it had come on) and I took the car to my Mechanic again. He connected the scanner in which the code P0420 was still appearing despite the light being off. So he cleared the code and asked me to drive and see if it comes back again. Since the light had automatically turned itself off. Does that mean that my cat is working still and there is no need to replace it? Is there any emissions test or something which I can get done to know the health of the CAT?
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Saturday, March 8th, 2008 AT 5:08 PM
Tiny
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My pleasure.

The mechanic is again right on the mark. Everthing is working as it should. Right now. I would suspect it will return.

There are other reasons for that code to come up, but I have yet to see it be other than the cat. The oxygen sensors are monitoring the cat. It would be good to have the wave pattern of the o2 sensors checked. They measure pre-burned gases before the enter the cat and then again after.
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Saturday, March 8th, 2008 AT 5:57 PM
Tiny
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Alas. The CEL did come back again but with a different code this time. The code which I am getting now is P0171 - Fuel system bank one too lean instead of the P0420 which I had got earlier. This code has come about 3 to 4 times now after I drive every 250 odd miles, however, last nite it came on barely after I had driven 37 miles after resetting it. I already had the MAF cleaned using CRC cleaner. My mechanic is also thoroughly confused since he also doesn't seem to have a clue. The scanner returns 2 codes but displays just P0171. Could it be the O2 sensor or something else? Please help me. There is no change in the performance or fuel efficiency of the car.
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Tuesday, June 10th, 2008 AT 9:40 AM
Tiny
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The testing procedure for the MAF is not accurate from the manuals, I would replace it if you can not find any vacuum leaks.
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Tuesday, June 10th, 2008 AT 10:37 AM
Tiny
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Are you so certain that it is the MAF which is the culprit here and not anything else? I have allready filled up a fuel injector cleaner about 2 months ago. Do you think I should check the O2 sensor voltage to find out if annything is wrong there?
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Tuesday, June 10th, 2008 AT 12:50 PM
Tiny
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I'm working off probablility. But these are other possible causes to go through:


https://www.2carpros.com/forum/automotive_pictures/30961_111af_1.jpg

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Tuesday, June 10th, 2008 AT 8:48 PM
Tiny
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Not sure if this got resolved but just wanted to add that when a toyota v6 starts setting a p0171 99.9% the maf needs replaced. Cleaning is typically a waste of time.
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Thursday, July 3rd, 2008 AT 1:47 AM
Tiny
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I concur!
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Thursday, July 3rd, 2008 AT 7:46 AM
Tiny
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That's a bull's eye.I have already replaced my MAF ( $ 160) and the CEL has gone. Have driven almost 500 miles after replacing it and there is no sign of the light coming back. Thanks to all of you for your time and expert advise.
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Thursday, July 3rd, 2008 AT 8:08 AM

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