harryfrank

Good Morning guys!

I had this 2 codes come and go a couple of times in the last month. po432 and po422. I noticed they came active as I stepped on the gas on a on ramp. after a couple of days they cleared by themselves. Again a couple of weeks later, They came back on.
Since both refer to the Main Catalyst Efficiency, one for the bank1 and the other for bank2. and they show up at the same time every time, would it be fair to say that the issue would be with the first upstream sensor? (Apparently I have 5 oxygen sensors total on my 2007 GL450, one main upstream, 2 upstream left and right, and 2 downstream left and right)
That would explain that both codes come up together since this one feeds info before the individual left and right upstream sensors. Has anybody had this problem before? Needless to say, my car needs all oxygen sensors replace. I do not recall ever changing one on this vehicle, although i bought it at 70k+ miles, it now has over 200k and kicking. My emission test is next month and need to try to get it through before changing all 5 sensors.

As usual, Thanks for helping!

lkchris

Don’t be so quick to blame the sensors.

Perhaps they are indeed correctly indicating they are receiving an exhaust gas mixture the cats can’t process ... meaning the problem is your mass air sensor. This is the way OBD frequently works.

Max Blast

May I recommend the Italian tuneup.

floor it repeatedly.

harryfrank

Since my beauty has 207,000 miles and vaguely recall perhaps having changed only 1 oxygen sensors since i've got it (probably at 75k miles. I have decided regardless, to put all new sensors. I will also in turn, clean the mass air sensor. But at this mileage, even the Cats could be just bad. ill keep you guys posted. (waiting on weather conditions to improve some)

harryfrank

Had a nice day weather wise last week, I was able to replace 3 sensors. After all my GL450 only takes 4. The last one to change requires some heat shield removal, so I'll do it in the next couple of weeks. Either way, as soon as I replaced those, I could see that the pending errors disappeared. then I went ahead and cleaned the mass air sensor. doing it in that order confirmed that it was in fact the oxygen sensors causing the issue. don't know which since i did all 3 at the same time though. I had unfortunately to remove the battery for some other work in the car, and I'm waiting for all systems to be initiated. it has been 3 days, and all systems are but the Catalyst. I know from experience that takes longer depending on conditions. So i will give it a few more days. It is my daily driver.

There is still no pending codes, so I know we are good. Besides, gasoline consumption is well minimized now. I found some readings from my scanner on the camshaft sensors and Variable solenoids that are bugging me, but i will open another thread for that. Will come back to share, when all systems are initiated.

harryfrank

Had to drive 15 minutes at a cruise speed of 55-70 mph without touching the brake to finally get the Catalyst monitor ok. Went to have the emissions test with one day to spare. The suv is running smooth. Passed the test with flying colors. Thanks For the support!

eric_in_sd

The oxy sensors are easy enough to replace that it's worth doing if they have more than about 100k miles - and you are getting errors. The cats do fail also. I still haven't figured out how to do the driver side upstream sensor.

FYI the cat sensors only are there to verify catalyst efficiency. The upstream sensors are the ones that do the heavy lifting in terms of mixture control. You typically won't get cat errors because of mixture problems, because the rest of the system has been checking what the mixture is doing and will report errors if it can't adequately control the mixture.