[BmwQuest]

Good Morning fellow Bimmer mates,

I have a basic 2019 G30 530i L4 and have a CEL that keeps popping up. I have a basic OBD II scanner that’s giving me a PO440 and PO446 readings. I have already replaced the fuel cap and after 60 miles the CEL popped up again with the same codes. I’m wondering if I should get a better scanner and will it give me a precise diagnosis and tell me what to replace? I’m thinking about replacing the O2 sensors but will I have to change the catalytic converter also? Please chime in and let me know your thoughts and suggestions. Thanks in advance for your help.

[lnxguy]

You need BMW specific codes (Not PCodes)

[BmwQuest]

Which scanner will give me the detailed BMW codes that I need?

[Qsilver7]

Originally Posted by BmwQuest

Good Morning fellow Bimmer mates,

I have a basic 2019 G30 530i L4 and have a CEL that keeps popping up. I have a basic OBD II scanner that’s giving me a PO440 and PO446 readings. I have already replaced the fuel cap and after 60 miles the CEL popped up again with the same codes. I’m wondering if I should get a better scanner and will it give me a precise diagnosis and tell me what to replace? I’m thinking about replacing the O2 sensors but will I have to change the catalytic converter also? Please chime in and let me know your thoughts and suggestions. Thanks in advance for your help.

Just curious if you did a search using what you posted or did you use the correct DTC (diagnostic trouble code)?

I ask because what you typed was PO440 & PO446…using the alpha character (pronounced as “OH’) instead of the numerical digit (zero). If that’s what you did and didn’t find any info…try again this time using all numerical digits after the “P”.

For example, type BMW fault code P0440 then BMW fault code P0446 into a google search box to see what results you get from other BMW owners searching for these DTC (trouble codes).

Good luck.

[BmwQuest]

Qsilver7 Thanks I appreciate it. That O was a type-o and I did do some research prior to making this post. Upon my search, I found that it could be the fuel cap, O2 sensors, catalytic converter,charcoal canister,or vacuum leaks. Hoping that it’s not the catalytic converter I made this post to find out if anyone here has experienced this issue.

Upon further research, I also found out that it could also be the EVAP vent valve at the charcoal canister or purge valve located under the hood. I’m thinking about testing the the purge valve since this seems like the easiest thing to do. Any thoughts or experiences dealing with these specific codes? Any ideas or suggestions would be much appreciated. Thanks in advance for the help.

[DrVenture]

These are relatively common codes across all makes/models of cars and most often they are caused by fuel cap, vent valve or purge valve problems.

You should test the valves as you said. The purge valve is the most common failure point.

[BmwQuest]

DrVenture Thanks for the information. Updates soon to come.

[DrVenture]

If you take the electrical connector off the purge valve and disconnect the hose to the evap tank, then start the engine, you should feel no suction (vacuum) at the nipple where the hose that you removed is normally seated. If you feel suction, the valve is stuck open.

[BmwQuest]

DrVenture Thanks for the quick test method. I was gonna take the whole thing off and test it. I’ll try your method when I get home from work. Thanks much appreciated!

[BmwQuest]

DrVenture Looks like it was the fuel tank breather valve under the hood. I replaced it with a new one, cleared the code, and after 60 miles no CEL. Currently drove 80 miles since the change, put my OBD scanner on it and 0 DTC is what it read. Hopefully this was the only fix it needed. Thanks for the advice. Cheers mate!