P0420 error - what should I do?

would tech stream be more specific?

 

You can watch the values of (front) air fuel ratio sensor and (rear) oxygen sensor with running engine to determine which is faulty air fuel ratio sensor, oxygen sensor, or catalytic converter. Catalytic converter is the most likely but also the most expensive. Unfortunately it's kind of hard to explain how to read the data basically you need to see how fast signals change depending on running conditions.

How much oil does your Prius consume? Engine oil consumption will slowly kill the catalytic converter.

Techstream is Toyotas own diagnosis tool. There is also a cheap Chinese version of that. But many general scan tools are basically as good when diagnosing engine (related) problems like this.

If it is the catalytic converter only legal options is to fit a new one.

 

yes, see valde3's response above. if you search here, you will find how and where to buy, along with advice on use

 

You bought a Bosch front O2 sensor instead of a Denso?

 

You really shouldn't use anything other than OEM sensor as the front sensor. Front sensor is air-fuel ratio type and differences between sensors can cause problems.

 

Given that, you should be checking the oil once a week (eg every Saturday) and adding 1 L when the oil is 2/3's down, which going by your information would be every third week.

It actually indicates NO oil and should not be relied upon as a warning. When this light is flashing, you should stop immediately and add 3.5 L of oil. Using this strategy, you have probably already caused damage to the engine, which only will be exacerbating the oil consumption.


PS:

Rather than that, you should just get your EuroCar Parts guy to source a Denso sensor that fits your car, or just go and get the correct Toyota (Denso) sensor from the Toyota parts counter.

 

Try an Italian tune up..
first the Cat is probably clogged up Don't replace it this is common this will burn off the carbon drive it in a lower gear DO NOT take it to red line but get it in the 3000rpm range turn off auto STOP



SWTICH oil brands some people have good luck switching to mobil1 oil full synthetic

 

Don't let the oil level drop! Oil pressure light tells that engine is already getting damaged. You letting the level drop has already caused engine wear and that has caused more oil consumption.

Oil consumption is measured against miles driven not time. But that sounds like a huge oil consumption.

With huge oil consumption there really isn't much reason to check signals from exhaust sensors. Oil consumption has almost surely caused the catalytic converter to go bad.

You mean oxygen sensor extender? They might be illegal where you live. It will help to keep the check engine light off for some time.But eventually the catalytic converter will be bad enough that it won't help anymore. That might have already happened.

Even if you don't care about the check engine light with high oil consumption catalytic converter will get clogged up at some point. That might already have started to happen.

And even if you fit new catalytic converter it will get poisoned and eventually clogged by oil consumption.

 

There is no way to drive a Prius in a lower gear.