P0420 and P0430 Codes???
 

Any idea what I need to look for/ fix for these codes:

P0420 Catalyst System Efficiency Below Threshold (Bank 1)
P0430 Catalyst System Efficiency Below Threshold (Bank 2)

I did a search and this is all the info I found. ^^

Most likely you need new cats. Unfortunately your emissions warranty has expired.

OK, found the info I needed:

A code P0420 may mean that one or more of the following has happened:

- Leaded fuel was used where unleaded was called for
- An oxygen sensor is not reading (functioning) properly
- The engine coolant temperature sensor is not working properly
- Damaged exhaust manifold / catalytic converter / exhaust pipe
- Retarded spark timing

Found helpful website: http://www.obd-codes.com

You have 100k miles, and I have found that the 02s go out around then. They can go longer but it would not hurt to replace them. You might pick up a little mpg too - and rule out or confirm that as the reason for the code.

If you can check the codes does that mean you can check the timing? If so you can confirm or deny that as well.

lo jack - thanks for the suggestion. I am also due for spark plugs, so I am going to replace those and probably all of the O2 sensors before I look into cat replacement.

Is there a DIY on O2 sensor replacement on here somewhere??

sounds like its the second set of O2 sensors downstream

I know this is an old thread, but I have both codes also. I have been searching on here looking for an answer, but am now @ wits end! My Vehicle is an 04 X5 3.0. Currently with just over 128,000 kms (80,000 miles)

Last August I purchased a 21' Malibu V-Ride (boat) in Ann Arbour,MI. Towed it back to Regina, Sask. (Approx. 24hours) She towed the boat no problem. Shortly after returning my SES light came on. The vehicle seamed to run perfectly fine. Since then I have been reading different posts on here and checking some similar issues other people have had.

So far this is what I have done:

-Changed the Plugs
-Replaced Coolant Temp Sensor (on bottom rad hose)
-Checked the DISA, MAF, hoses do not see any major issues
-Replaced O2 sensors before the cats, had the codes cleared, SES came back on
-Replaced O2 sensors after the cats, had the codes cleared, SES came back on

I though I had finally had it cased on this last one, but the SES light came back on again this morning. It seems the SES light returns around the same time after I have the codes cleared.

If it the cats, would the vehicle still run as well as it is?
Do I need to look further into MAF boot, sensor & components?

Any help, suggestions would be much appreciated!