P0420 and P0430 on X5
 

Hello BMW owners

I have 2002 X5 3.0 . Sometime back SES light turned on and when I checked the code it was P0420 and P0430 .

My mechanic suggested replacing O2 sensors as it was already 88000 miles. After replacing O2 sensors the car went fine about 1000 miles and I got the SES lights turned on again . Same codes again .

The car runs absolutely fine with the exception of poor gas mileage . Around 16.2 City .

So My question is what tests can I do to verify if the cats are working fine ?

What could be other cause of these codes and how to rectify ?

Thanks
Sunil

i have a chance found the DTC table, it can help you understand the meanning of the fault codes, you can have a look.

To do a quick simple test on the cats, run the vehicle for a cpl min. Place your hand over the exhaust pipe. If the air coming out is extremely hot theres a chance you have a plugged cat. That would also explain the bad mileage and o2 sensors. Same exact scenario happened on a old vehicle of mine.