Just bought used Prius--check engine light now on...

don't know the code, but check the gas cap for tightness. should be one click.

 

how many miles do you have on the car?

 

genII is not 1 click, it's a regular cap, need about 3 clicks

 

you should regularly check the oil level on the car as well. they tend to burn oil at that mileage and you don't want to run low.

If it is the gas cap, you would need to drive it about 30 minutes or more before it turns off.

 

Those codes mean nothing, and are for the Audio/LAN system only, not about any other systems. In order to read the DTC's in general, you need to get a Prius specific code reader, like the mini VCI. For just the check engine light you can get a scan at Autozone for free.

 

That is rather too soon for the cat to go, and very rare. Too soon for the O2 sensor as well, but maybe more likely. There are other threads here that mention this. What exact code was read?

 

What state are you in? Since this is an emissions related repair, check with your local dealer to see if there is any warranty coverage for the cat

SM-N900P ?

 

Tightening the fuel cap one click is sufficient.

If the car was originally sold in California and continuously licensed and operated there, then it qualifies for warranty coverage under the more generous California warranty. In that case the catalytic converter may still be covered under warranty.

If not, I agree that it makes sense to replace the air/fuel ratio sensor upstream from the catalytic converter first to see if that helps. The reason it may help is if a new A/F ratio sensor is more responsive to changes in the A/F ratio than the existing sensor, that will help the engine ECU to conclude that the catalytic converter is functioning in an acceptable manner.

It seems reasonable that a new catalytic converter will cost $1K because California does not allow installation of an aftermarket cc which does not meet California standards - and those standards are relatively rigid, having to do with durability of the replacement part.

The engine should be evaluated to see if it has a problem. The iridium spark plugs should be replaced now if that service was not earlier performed. An engine misfire, or an engine which is burning oil, will introduce more unburnt HC to the catalytic converter which will cause it to overheat and wear out sooner than it otherwise might.

 

Does this car have a clean title? Is rare to hear about people buying these Hybrids without seeing them in person.

Hope it works out for you, one lucky thing you have in California, the car is exempt from Smog inspections (to register the car into California) so you have plenty of time to sort out the problem.

SM-N900P ?

 

Well, since the check engine light was lit, you had the DTC scanned and you were told the car needed a new catalytic converter, I assume that the only code reported to you was P0420. If that assumption is not correct then please report what the logged DTC were.

If no other DTC were logged, that is not sufficient evidence to assume that all is well given the failed catalytic converter. You should remove and inspect the iridium spark plugs to determine their condition. You can tell a lot about an engine by looking at the used spark plugs: whether the engine is burning oil, whether the air/fuel mixture is too rich or too lean, whether a cylinder is operating poorly compared to the other three.