CEL, dealer says I need new catalytic converters

I have a 99 SOW with 105K miles. This past weekend the CEL came on and I took it to the dealer. They say they pulled code P0420 (Cat efficiency below threshold bank 1), and told me I need to "replace catalytic converters and possibly both sensors and hardware."

I've done some reading on this topic and I have a few questions that I hope someone could answer. First off, I'm a bit uneasy about the vageness of the diagnose. It sounds like they're not sure whether it's a bad cat, a bad sensor, or a bad gasket. I don't want to pay $1200 for the job if all that's really necessary is an exhaust gasket or a new O2 sensor.

Is it normal that both cats go bad and need replacement at the same time? How easy and expensive would be to just replace the sensors and the gaskets as a first step? Does the P0420 code really mean "bad cat, must replace" or is it just an indication of different readings between the 2 sensors (which may or may not be due to a bad cat)?

Any suggestions on how I should proceed?

Thanks in advance,

- Manuel.

Reply to
Manny
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Unless your vehicle is burning oil, it is very unlikely that your catalytic converter is worn out.

Try testing the O2 sensors first.

Was the 0420 code the only one?

Good luck!

Manny wrote:

Reply to
AS

I would do this incrementally I think, change front O2 first (it get's more heat and more contaminants if there is a headgasket leaking.). Reset the ECU, drive. If the CEL comes back, change the rear sensor.

A good mechanic can test the sensors to see if they are 'lazy'. It IS possible to need a converter at 105K - just not likely if the car has had no previous 'issues' and has otherwise been well treated.

Carl

Reply to
Carl 1 Lucky Texan

This is SO TYPICAL of Subaru's service/dealers. Get a second opinion, DO NOT mention to them you have had a quote from another dealer. See if they come to the same conclusion (bet they don't). At 105,000 Miles the O2 sensors probably ARE dead. You can buy the Bosch replacements from "Autozone" if you have one nearby. Call around, they vary widely in price.($40 at Autozone/$65 at Pep Boys) You can do them yourself, not hard to replace just do it with the car stone cold. The O2 (oxygen) sensor(s) is a good place to start.Remember to clear the codes after you mess with it. In fact.....I would clear it and see if it comes back again. Some autoparts stores will pull the codes for you for FREE. "Autozone" is one of them.

Reply to
Backfire Bob

Reply to
Edward Hayes

Hi,

I'll attest to the possibility of a short life expectancy of an aftermarket cat... limped home at 3 mph and VERY hot exhaust system (didn't damage car, but could have if I'd had to go very far--an acquaintance burned up the carpet in his vehicle under similar circumstances) when one self-destructed and blocked the entire exhaust system. Factory cat is "cheaper" in the long run IME!

Rick

Reply to
Rick Courtright

You guys have been a great help. Thanks a lot for all the replies. I will try replacing the forward O2 sensor first and go from there, assuming I don't see any major visible damage to the cat. I haven't looked under there yet but I live in New England, so a damaged cat or exhaust gasket due to corrosion is always a possibility.

One more question. How do I reset the ECU? Do I need to take it back to the dealer for that or can they do it at AutoZone? Will unplugging the battery reset the ECU? The dealer did reset the CEL this time an it hasn't come on in the 50+mi that I have driven so far.

- Manuel.

Reply to
Manny

If P0420 is the only code, my guess is the O2 sensors are OK as they have their own codes if they go bad.

Not unusual that both cat converters are combined into a single assembly.

With the miles you have on your car it is likely you will experience the CEL coming on and then go off again. The freq and time the CEL stays on will increase. That is how mine behaved and light has been on steady for many months until recently went off for a couple days.

If you attempt to replace the converter yourself, it's not an extremaly hard job. There are a number of mfgrs now offering cats for the Subaru. Inquire what the length of the warranty is. Ive' seen some saying 25k miles and other 50k miles. Prices can run from a little over $200 to about $750 for a factory replacement. Again if you do undertake this yourself, DON'T buy a Eastern Catalytic brand. Not a great fit and front O2 sensor mislocated where it hits the CV joint. I'm still working on getting my money back on one of these.

Mickey

Reply to
Mickey

Reply to
Edward Hayes

Sometimes you can talk the A'zone guy into resetting the ECU (they are reluctant in some states due to emissions testing and especially sales of used cars. - maybe take him a cold Modelo Especial! If not. Ed's technique should work.

a good on-line discount dealer for an OEM cat is

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Not the only place to shop - just one I have been happy with. Email Jamie there for any questions. She's great. AND a Subaru rally racer!

Carl

Reply to
Carl 1 Lucky Texan

You can also buy a code reader that will reset the CEL light for around $50. I got one just to keep in the car. If the light comes on at least I'll have an idea whether it's okay to keep driving it. The readers generally give you a CD or book with a list of codes. You can also find them on the Net.

Reply to
Sheldon

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