I have had a 2007 GS300 for a year now and have had no problems with it with no engine management displays.
Today a friend put his new gadget on it - an OBD reader - and it identified 2 'pending' errors.
P0420 and P0430.
My understanding from researching the codes, is that they are identifying either faults with the sensors or an upcoming failure of the catalytic converter.

Am I correct?
If not, what else could be the issue
If yes, which is more likely, faults on the sensors or a failing cat.

Any thoughts welcome.

 

Exhaust leaks, bad sensor, bad cat.

The first two will make the car think the cat is bad

This is the sequence of diagnosis.

read this thread https://www.clublexus.com/forums/is-...-bank-2-a.html

 

Thanks you for the info.
I did not know that there were 2 cats on the car.
So if both sensors are recording faults then is it more likely that it is an exhaust leak rather than either both sensors or both cats - or am I not understanding how it works.

Also - and this may not be relevant - the car was stood up for 3-4 months until a couple of weeks ago - could it be that not having been driven for a period may have affected the system?

 

Our cars have actually 4 cats 2 on the exhaust manifold header and 2 on the mid pipes. I would just clear the codes and drive the car and see if they come back on later. More likely because the car sat for awhile, the sensors got dirty by the environment. But I would do a top engine cleaning, by running seafoam through the intake manifold vacuum. This should help clean out some crud out of your engine and exhaust. While youre at it, might want to pull the throttle body and clean that and maybe put some fresh spark plugs in it.

 

Thanks for that.
When I checked this morning, not having cleared any codes) only one code was now showing - a pending (P030). No other errors were recorded in history or active - which puzzled me.
Afterwards I cleared all codes and have driven the car for about 30 miles since with no codes having re-registered. I will keep an eye on it over the next few days and see how quickly (if at all) they return.
I will also follow your other suggestions and monitor the results.

Thanks again.

 

Well here we are 100 miles later - and still no error codes.

Hopefully it was dirty sensors which were 'cleaned' when the car was driven more regularly.

Will continue to monitor.