Fault Codes 420 430 On A 4.2

[flyboyprowler]

So the woes of the eml light go on!

Having just replaced the 4 O2 sensors, and all seemly tickedy boo. We have just had an 8 day trip through France back to the Spain, doing around 5 hours a day of mixed driving, and halfway back the light came on again, off the next day and finally on permanently. Codes 420 and 430 only

I have checked back on the forum and know that the gasses have to be checked, and hopefully there is a local hombre here in Spain that can help. However, the car has now done 143000 kms, and is 10 years old, and in replacing the O2 sensors, would these shiny new beasties be working so efficiently, to tell that the cat is shot. It seems strange that this new warning should happen after doing the previous work. It is also unlikely that the car has had the ecu upgrade, so could this be the first place to start?

The car is running fine, economy is normal, so any extra thoughts would be much appreciated.

Muchas thank yous,

Ainsley, gently melting in Spain!!