2002 Prius needs catalytic converter?

Yesterday I was driving on the highway, 65 mph and the CEL came on and I immediately went to the Toyota Service center. They ran a diagnostic test and the following codes appeared, P0300 thru P0304 (pending) and P0420 (Current,pending and history were checked). They said I need a new catalytic converter at a cost of 1900 dollars and would soon need 02sensors. When I left the CEL was no longer on so I don’t know if I really need a new converter or not. I only have 86,000 miles on the car. Should I bite the bullet and let them replace the converter?

Short answer is no. If the car is not under extended warranty of sorts, I would not go to the dealer. I do not think your cat’s are bad at that low mileage, but I guess anything is possible. Do you know if they reset the computer or the light just went out on its own?

Either way, wait until the light comes back and then get a 2nd and 3rd opinion. There was a similar post just two days ago, so if you search the threads, you will find a lot of useful info.

The method used to check the cat function is for the computer to monitor a pre-cat O2 sensor vs a post-cat O2 sensor. If the expected relationship isn’t observed between the two signals, that usually means either the cat is bad, or one or both of the O2 sensors are bad. I presume they’ve checked the O2 sensor functions and found them to be working correctly, so they think the cat is bad. Unusual at 86,000 miles, but Prius is a special type of car that doesn’t use as much gasoline as a non-hybrid, so maybe the cats are less robust in them.

One other possibility is the cat is indeed bad, but it is bad for another reason, and if that other reason isn’t diagnosed and fixed, replacing the cat will be a fools errand, and the new one will foul for the same reason, just like this one did. Good idea to ask about that, see if there is a test they can use to disprove it as a concern.

In some states (California is an example) the state rules require emissions equipment, such as cat converters, must have long warranty periods. Longer and more miles than you might expect. If you live in one of these states, it may be the dealership will be required to replace the cat under the state’s extended emissions equipment warranty. Make sure you check up on that before paying for it on your own.

Have you had any driveability problems lately? The P030X codes are for engine misfires. When a Prius misfires it is very obvious. It is also extremely rare to see a Prius with a cat code since the engine runs only a small portion of the time.

The 0420 is for low catalyst efficiency, but the others are for misfires, one code for each cylinder. If the cylinders are misfiring, it can throw up a “red herring” 0420 code.

I would, with only this information, consider the cat code to be a “red herring”. My guess is that when you fix the misfire root cause the cat code will disappear on its own.

It might be as simple as a need for new spark plugs. I’d suggest taking it to a reputable independently owned and operated shop for a look-see. My guess is that the dealer guy saw the 0420 code and immediately said “cat converter”. They often do that.

I agree with @the same mountainbike on this.

Look at it this way the Cat is at the end of the line so a bad Cat would not throw codes for misfires. That must be a separate issue. Start with the misfire on #4 (P0304) as the P0300 is a random misfire code which is probably for that same cylinder.

Then have thew codes cleared and see if the P0420 comes back.


Whoever did the dealer diagnosis is a moron or a crook.
Trouble codes should be dealt with lowest number first. They were thoughtfully arranged this way.
Fix the misfires and the P0420 will likely go away on its own.
My first suspicion for multiple misfires in this engine is a leaky intake manifold gasket, which tends to rear its ugly head in cold weather.

Has your fuel economy dropped significantly lately without any change in your driving habits? Sometimes the car will see low efficiency of the catalyst and run the engine more/longer in an effort to keep the catalyst at operating temperature in order to keep catalyst efficiency up.

However I would address the misfire codes first. Had you noticed any difference in the way the car was running or driving?

BTW, a diagnostic test involves actual testing with lots of equipment, just reading codes is something any monkey with a cheap code reader can do.

I want to thank everyone for their input, it was very valuable info, saving me a lot of money.

The CEL has not come on since. Does speed have anything to do with the CEL coming on if it is the catalytic converter

Speed, yes…The faster you go, the harder the cat works…But they are designed with that in mind…Change your spark plugs. 86K miles is long enough…

Oh, does the Prius need plugs changed at 86,000 miles? My 2002 Sienna does not even specify that often for plugs, and it runs great at 213,000 miles.

Probably not IAW the manufacturer’s recommended maintenance schedule, but I’d recommend it anyway. When one is having misfires it’s always good to revert to basics.

Besides, that’ll provide an opportunity to “read” the plugs, which in itself can yield clues. I personally would be very interested in seeing photos of the plugs if the OP is up to it (if there’s oil on a plug, please don’t clean it before taking the photos). You never know what you’ll see until you look.

I have an ulterior motive for requesting that the plugs be photographed “as-is”. Oil on a plug might suggest a leaky “O-ring” at the bottom of a spark plug tube, a simple and affordable fix.

The spark plug tube on the Prius press into the cylinder head and have sealant applied to the sides. The one possibility not mentioned yet was having e85 in the gas tank the ecm on the Prius does not have mapping for ethonal fuels. The Prius drive train is unique and when the engine does actually misfire it is very obvious.

Irlandes, are you saying your Siena has the original plugs at 213k miles?