P0420 Trouble Code ??

Hello,

I have a P0420 trouble code, that says "Catalyst Efficiency Below Threshold". Can any one give me an idea on how to raise the efficiency of the catalyst? My car is a '99 2.5L Legacy Outback wagon w/ 113K miles. Is this trying to tell me I need to replace the catalytic converter on the exhaust system? Sounds like it going to hurt my wallet. I've searched past posting and didn't find anything. Anny and all help is appreciated.

Thanks

-Nick

Reply to
Nick Lamendola
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Yeah sorry you can't raise the catalyst efficiency, that code is telling you the catalyst is shot. At 113K that is not surprising. Unfortunately you are well past the federal emissions warranty period of 8/80 or you could have gotten a new one for free. Depending on what state you reside in and whether you need to pass inspection, you may be able to forgo this repair at least for the time being (as long as you don't mind staring at the light) or you may have to do it to pass emissions.

Reply to
mulder

Thanks mulder, I really didn't have much hope in raising the efficiency. I'm just happy that my car passed NYS inspection last month. No new inspection sticker in NY with a check engine light on. :( I don't mind having the catalytic convertor replaced as long as that makes the code go away. I read where it could be caused by an exhaust leak. Any idea if muffler shops can test a catalytic convertor? I hope it is not an issue with the O2 sensors, as that sounds like it can get you chasing your tail. Thanks again,

-Nick

Reply to
Nick Lamendola

That's true. If the leak is before the catalytic converter. Its a much cheaper fix though, so I'd have that checked before going to replace the catalytic converter. If the O2 sensor goes, it throws its own code.

Reply to
JD

Just out of curiosity, what kind of driving style do you have?

I would imagine smooth driving.

Nick Lamendola wrote:

Reply to
AS

First, you MAY have a bad converter - however, there is a very great chance what you have is a 'lazy' or bad lambda (O2) sensor. Has an O2 sensor ever been changed on your car? Also, if you clear the code, do you get an immediate return of the CEL? The only way the ECU can detect a bad converter, is comparing signals from an upstream and downstream O2 sensor. If one of these sensors is bad (or associated wiring) you will get that code. The diffence in cost between a new converter and a new sensor is close to an order of magnitude. So, even if you can't actually get someone you trust to test the sensors (easy with a scope or even some meters) it is likely still worth the gamble to change the sensors. If you know neither of them have eever been replaced, definitely change the front one first and drive/monitor the situation. If the front has been replaced in the last

50K miles or less - it may mean the after cat sensor needs replacing.

don't panic!

Carl

Reply to
Carl 1 Lucky Texan

Thanks Carl, I'll take your advise. Neither O2 sensor has been replaced. I cleared the code and it hasn't returned in my normal 70ml. round trip commute to work today. So maybe it was just a fluke, it happend right after I gassed up my car. If it does come back I'll start with replacing the O2 sensors.

-Nick

Reply to
Nick Lamendola

Nothing too hard, I rarely push it, mostly express way speeds, commuting to work and back. Why do you ask?

Reply to
Nick Lamendola

I asked because when engines are not driven under demanding conditions, carbon tends to build up on pistons and valves. Sometimes, deposits can also be formed on oxygen sensors and catalytic converters, when cars are driven for short distances, not allowing all these components to get real hot.

One problem i remember due to this was the 4 cylinder camry engine, 95 model and similars, which used to develope a sticky valve syndrome, killing one of the cylinders...

In your case, express way speeds would exclude this as a possible cause for your problem and I second carl's suggestion.

Good luck

Nick Lamendola wrote:

Reply to
AS

Due to mileage I'm betting on bad converter. There is also a code for bad O2 sensors so if you are not seeing that in addition to the P0420 code my money is on the converter.

Mickey

Reply to
Mickey

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