Hello everyone, my 1995 Legacy Outback (340K miles now ) has thrown the dreaded PO420 code, I noticed that Subaru has discontinued OEM catalytic converters. Is there a replacement OEM part # or will I need to go aftermarket? If I need to go aftermarket, what is a quality company to purchase replacement CC's from? Thanks for you help. I am the original owner of this car, it just keeps running so well, no need to replace it!

things as simple as an exhaust leak or cleaning a MAF sensor have cured that code for folks - we often tell people that the cat is rarely the problem but, at 340K, yours may very well be 'done'. Same for the rear sensor.

 

worth looking around for other issues first as even aftermarket cats are pricey. Some folks also have use - spark plug 'extenders' and resistor networks to turn off that code. The rear sensor that triggers it is ONLY used for cat monitoring and has ZERO effect of the car's running parameters.

Thank you very much for your reply, I'm going to check for exhaust leaks etc. first. Cleaning the MAF is a good tip, I'll try all the simple things first. Then replace the O2 sensors and then the cats if necessary. I still want it to pass smog out here in California 

vacuum leaks, bad wiring,etc. , all that needs to be considered as possible P0420 causes.

 

If it comes down to the cat, you might consider a low miles unit from a junkyard - California cars may not have killer rust and swapping-in an OEM cat should be doable. You may find one with 1/3 the miles of yours at an affordable price.

 

car-part.com and LKQ are possible sources. I think there are ways to use an infrared thermometer and perhaps determine if the cat is lighting-off - check youtube for that.

How's the gas mileage and performance?

 

P0420 is generally benign unless it's accompanied with bad gas mileage or performance.

 

How much longer do you plan to own the car?

 

Being in good tune is helpful. If it needs air filter, plugs and wires then do those.

 

PCV valve is super easy and cheap.

 

If O2 sensors are ancient those a good try and particularly the front sensor can improve gas mileage a tiny bit (or much) so it can recoupe the replacement cost over the life of the vehicle. So I see things like this as good chances to update important parts.

 

Testing O2 sensors wouldn't be a bad idea or just replace them but you might not want to just replace parts depending how long you're keeping it.

 

But yeah if you don't want to throw parts at it you have some testing to do or throw a catalytic converter at it - that generally fixes it even if it's partially tune/performance related, the new converter may be more forgiving.

 

Used is an option but probably not in CA, some places don't sell them and I doubt CA is easier.

 

I've used aftermarket before without issue, even cheap eBay specials, though I'd guess that's hit or miss. Walker?

 

The catalyst material is expensive so if it's cheap and no compelling reason it's cheap it's probably a low grade unit with limited catalyst materials.

Gas mileage is still decent (24-29 mpg depending on how much highway driving I do) performance is certainly not what it was when the car was young but it doesn't seem to have degraded to where I feel it is down on power. It doesn't miss and still runs smoothly, I'm most suspicious of an exhaust leak which is what I'll check first. t'll work through these suggestions and see what happens, thanks for all the help 

vacuum leaks, bad wiring,etc. , all that needs to be considered as possible P0420 causes.

 

If it comes down to the cat, you might consider a low miles unit from a junkyard - California cars may not have killer rust and swapping-in an OEM cat should be doable. You may find one with 1/3 the miles of yours at an affordable price.

 

car-part.com and LKQ are possible sources. I think there are ways to use an infrared thermometer and perhaps determine if the cat is lighting-off - check youtube for that.

State laws vary. Here in Indiana, it is against the law for a wrecking yard to sell you a used cat converter. Getting caught, the yard is subject to a large $ fine. Maybe California law is different??

That would be a switch, if somebody had more restrictive laws than CA 

Just as a follow up, I deleted the code and it has yet to return almost a month later, it may have been a random event but I'll keep watching for it just in case.

msg