P0420 & P0430 Codes Help!!!!

[Feeze]

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 seems to run perfectly fine, still lots of power & no noticeable change in MPG.

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?

The only other hiccup was a couple times during the winter when it was really cold my temperature guage shot up like crazy. Pulled over, shut the vehicle off for a couple minutes, restarted and the problem went away. That is why I changed the CTS.

Any help, suggestions would be much appreciated!

[Penguin]

FYI:

P0420 Error Code: Catalyst System Efficiency Below Threshold (Bank 1)


Did you replace the O2 sensors with BMW OE sensors, or aftermarket sensors, such as Bosch?

I have not worked on BMW's very much yet, but some other makes are quite sensitive to the O2 sensor specs, e.g., Bosch O2 sensors frequently do not work on Fords, even though they are the correct Bosch recommended sensors.

Of course, it could be exactly what the code is there for -- your converters could be toast. I am not familiar with Canadian laws regarding leaded gasoline. I know some countries have allowed gasoline for marine use to continue to have some lead. Any chance you got some leaded gasoline in there that was meant for marine use?

[THK]

Get to a repair facility that has graphing capabilities on their scanner. If the rear O2 sensors are mimicking the front O2 sensors then the cats are dead. If the cats are good the rear O2 sensor pattern is usually a flat line.

[Feeze]

Thx for the response Penguin!

I did replace the O2 sensors with the aftermarket Bosch.I have read where other members have used the aftermarket ones with no issues.

We do not have leaded gas available in Canada.

Could the problem be in the MAF sensor?

[Penguin]

Originally Posted by Feeze

Could the problem be in the MAF sensor?

Highly unlikely.

As THK said, the error code indicates the pre and post cat sensors are likely mimicking each other, which implies the cat is doing nothing. While I hesitate to say anything is impossible, I do not see how a MAF could cause these codes to be set without triggering other "too rich" or "too lean" codes as well.

The real-time comparative look at the output of the pre and post cat sensors suggested by THK could confirm a "bad cat" diagnosis.

P.S.

This link has a rather poor, but readable, comparative graph of good and bad upstream (pre cat) and downstream (post cat) O2 sensors:

Tech Feature: Acquiring Data on Scan Tools, Part II

[Feeze]

I'll see if I can get a proper scan done. If the case is "bad cats", do I need to take the vehicle into BMW, or can I do it myself?

Thx in advance!

[Feeze]

http://www.xoutpost.com/bmw-sav-foru...-needed-2.html

This is where I got the MAF idea?

Am I confusing the issues?

[THK]

First, deal with the codes you have. You have already spent your hard earned dollars on new O2 sensors and have the same codes. While several other items may contribute to these codes, before you spend any more money on shot gunning repairs, get the the O2's checked as noted in my previous post. If the cat has died, I would of recommended to replace the sensors with the cats too. They do get tired and lazy in their output. Especially the front sensors. But you have already replaced them.

If you do find a shop to test the O2 sensors, they should be able to see what the temp sensor reading is and be able to check the MAF too with a press of a few buttons.

A lot of exhaust shops may be able to help you. They deal with this all the time. Be careful. If the cats are dead, they will have some aftermarket units to replace the factory ones. Make sure they are the right size for your vehicle. Or go with OEM.

Best of luck to you on this

[ewebby]

I had the P0430 and I just bought Mass Air Flow cleaner and cleaned the MAF sensor and it did the trick. Try this first, the cleaner is $5 at auto parts store. This gets triggered because if you use an oiled air filter, over time the sensor gets build-up.

Spoke too soon, came back on.

[james520]

error code table: Diagnostic Trouble Code Table