Hello there, I recently bought a GS300 and don't know much about them. I have a 2002 GS300 and recently my CEL came on with the codes p0420 and p0430. Ive done some research, and found it could be anything from my negative terminal on my battery to the catalytic converter. Before I waste a bunch of time, I thought I would post here and ask, what is the most common part that has to be replaced for this light to go off?

Thanks everyone

 

Hello, and welcome to the forum. The best way to find the most common cause is to start reading the various GS - 2nd Gen forum threads for each of these codes and see what each member has done to correct it. The information /education your get from this will likely save you time and money diagnosing and repairing the cause of the trouble codes.

Search each code number separately for the most possible results.

 

For the P0420 it is most likely it is the cat, I've had O2 sensors go bad, but rarely.
Disconnecting the negative terminal would reset the ECU and turn off the CEL, but it will trigger the light once the parameters are met to test the cat.
If it needs an emission test the tech will know that the the battery was disconnected and will probably charge you and tell you that you need to drive it for the ECU to run the test.