[LuckyOnTheDucky]

2007 328i stock everything, 190k miles.

The P0420 & P0430 codes are becoming more persistent. (always occur together)

Do these codes always mean bad cats, or can bad O2 sensors also be a possible source of the fault? If so, is there a method to tell which it is?

Thanks!
L

[AngelFarelli]

Could mean an unmetered leak within exhaust system or bad sensors. You could do a leak test

[gbalthrop]

Originally Posted by LuckyOnTheDucky

2007 328i...P0420 & P0430 codes are becoming more persistent. (always occur together). Do these codes always mean bad cats, or can bad O2 sensors also be a possible source of the fault?

Time to learn how to use Freeze Frame Data on whatever scan tool you are using to read those codes.

Most any decent P-code reader will ALSO give you Freeze Frame Data showing, among other things, ECTS (Engine Coolant Temp Sensor) signal as received by the DME at the moment the code was saved ("Snapshot" of engine conditions at moment Fault Code was saved in DME Memory). My SWAG would be that your ECTS value is in the 150F to 170F range and the SES light is coming on ~ 10 minutes or more AFTER you started the drive.

That code commonly occurs when engine is NOT reaching normal operating temp after run-time in which it would be expected. That is most often due to a failed thermostat, failed OPEN thus preventing restriction of coolant flow through radiator to regulate engine temp.

You can also activate "Hidden Menu 7.00" which displays ECTS value as received by the DME, and watch what happens as you drive. This is a bit of a hassle, as you have to do the activation process each time you turn on the ignition, but it's the easiest way to observe Live Data or ECTS Parameter as you drive. Confirm with FF Data from Scan Tool. Also note how long after cold engine start until SES comes on when you previously cleared codes. Here is the Procedure for Hidden Menu:
http://e90.wikifoundry.com/page/BC+hidden+menus

Since you have the SAME Fault (Cat Efficiency) on BOTH banks, and they both got progressively more frequent at the SAME rate, it would NOT be reasonable to expect either the Post-cat sensor, or the Cat itself, to fail on BOTH banks at the same time. What are the odds of that?

ANY other DME Codes?

Please let us know what you find,
George

[LuckyOnTheDucky]

The thermostat is fine, warms up quick and maintains 200 deg. The codes self-cleared the other day. I may try some snake oil fixes (SeaFoam/Cataclean) and keep my fingers crossed!

[gbalthrop]

Originally Posted by LuckyOnTheDucky

The thermostat is fine, warms up quick and maintains 200 deg. The codes self-cleared the other day. I may try some snake oil fixes (SeaFoam/Cataclean) and keep my fingers crossed!

I don't mean to sound like the ONLY thing that can cause P0420 & P0430 Codes is running too COLD, but it is ONE thing that CAN.

Did you check the Freeze Frame Data (Snapshot of engine conditions at moment those two codes were saved which include ECTS Temp Signal) for either of the two codes?

I don't understand exactly what you mean "the codes self-cleared the other day." Generally Fault Codes saved in DME Memory do NOT just "fade from memory" and only are NO LONGER there to read when they are CLEARED by a Scan Tool or Software.

Warning Lights on the Dash, such as the SES, can go out if the Fault (cause of the code) is no longer present, but the Fault CODE remains in DME MEMORY until CLEARED. "Misfire" codes or other intermittent "Faults" are a good example of that. If one uses INPA software to read Fault Code Details, there is ALWAYS an indication of whether the Fault is "Currently Present or NOT/nicht." If one sees P0420 as a Fault Code saved in DME Memory, but the SES light is OFF, one would expect to see the Fault Detail that says "Fehler momentan nicht(NOT) vorhanden" = "Fault NOT currently present"

So UNLESS you look at the FF Data ("Snapshot") and ECTS or Engine Temp (one of the Parameters saved in FF Data) at the moment the P0420/30 codes were saved, you don't know WHAT the engine TEMP was at the moment either code was saved -- and THAT information is critical. If NO ONE CLEARED either of those codes from DME Memory, they are BOTH still there, and SO IS the FF DATA. You need EVIDENCE to prove or disprove ANYTHING.

George

[LuckyOnTheDucky]

The only evidence I have is that the SES light is not on. My VERY basic code reader does not have freeze frame.

[aceshigh]

I'm battling the same issue and codes. 09' 328it with 137k..checked the coolant temps (thanks to George for that recommendation), and they hovered between 90-93 Celsius. Last ditch effort..ran catclean 3 days ago. Ses light has gone off this evening (after approximately 200 miles on and off driving). My guess is the cats are on the way out, and my light will come back on. 😒

[LuckyOnTheDucky]

I tried both SeaFoam and Cataclean. Definitely not a fix, but the SES light SEEMS to be spending more time unlit.
I am still intrigued as to why BOTH 0420 and 0430 codes occur at the same time, everytime.

[Moisture]

Failed/bad cats and o2 sensors are almost always the result of a rich running condition from a misfire or excessive oil consumption

[LuckyOnTheDucky]

Using E-10 fuel seems to help immensely.

[scotty325]

Got P0430 and SES light - no other codes.

Captured the FF data gbalthrop I’m hoping you may be able to give me a pointers on what could be happening from these? 🙏

I’d rather go fiddling with o2 sensors than be up for a new cat - but ce la vie


Thanks

[scotty325]

From my reading online the only thing standing out to me thus far - still reading and trying to understand more - is the Long term fuel trim showing a high negative value and therefore the ECU seems the engine to be running rich and is therefore adjusting to this? Time to go back to the search engine to get more knowledge 😅

[gbalthrop]

Originally Posted by scotty325

Got P0430 and SES light - no other codes. Captured the FF data...

I have never had to replace a Catalytic Converter in ~ 40+ years of use in vehicles with 50K to 150K mileage. ALSO, I have never spent much time learning about Fuel Trims, & other related data, so hardly an expert on issue. With THAT Disclaimer, here are my thoughts:

1) Any History of either (a) Impact damage to Bank 2 Cat, or (b) misfire on Bank 2 cylinders (4,5,6), where unburned fuel may have been dumped into Cat, causing fire & melting of catalyst?

2) See suggested inspection/ diagnosis in "Service Notes" of Fault Info Sheet for P0430 | 29F5 Fault Code:
https://bmwfault.codes/XMLDiagView?d...QAMAA3ADAANAA=

3) After SAVING the FF Data, Clear the Code & see if it returns.

4) Summary of FF Data (what appears significant to me):
a) Your 1st FF Screen shows "OL" = Open Loop or NO O2 Sensor Trim, at 96C (ECTS) & 2.7% Load; Is that "Over-run" condition?
b) 2nd Screen: STFT = 0.0, Both Banks; LTFT = .8% Bank2; RPM = 1,287;
c) 3rd: Speed 61 km/hr = 38 MPH; Spark Advance 30 degrees (?) Throttle Position = 14%
d) 4th: Engine had run 1012 seconds, nearly 17 minutes (and had reached 96C Coolant Temp)
e) 5th: Load, calculated based upon MAF & RPM values(?) = 13.3% (roughly same as 14% value above); TP generally means Throttle Position. WHAT "TP_R" & "TP_B" mean?? Learned Throttle Position? Absolute Throttle Position? Accelerator Pedal has TWO Hall Sensors, and values are SUPPOSED to "Correlate", one approximately 2x the other in voltage of signal. Meaning of "Lambda 1.999" (when you have FOUR O2 Sensors & OL), I have NO Idea. It COULD mean too LEAN (AFR twice what it should be, which is 1.0)? But WHICH Bank?
f) 6th: TIRED of GUESSING! Any clues in your Scan Tool Manual as to WHAT those abbreviations MEAN?

Please let us know what you find,
George

[scotty325]

Thanks George, really appreciate your detailed response!

I’ve been trying to get to grips with the meanings of all of the abbreviated codes on my OBD data.

I noticed that during live monitoring the voltage of the downstream o2 sensor is a bit bezerk. The guy in this video explains in a clear way how to interpret this: https://m.youtube.com/watch?v=aTNhxv...bnZlcnRlciA%3D

Which leads me to believe the cat is fouled or blocked - not working properly anyway.

I plan to take the upstream o2 sensors out and run the car briefly - if the car behaves as though it is able to breathe better and the power seems to have returned I think this will be confirmation it’s time for new cats or some kind of alternative.

🤞

[gbalthrop]

Originally Posted by scotty325

... I noticed that during live monitoring the voltage of the downstream o2 sensor is a bit bezerk...

Please define "bezerk":
What range of readings?
Random fluctuation, or related to RPM (particularly RPM decrease/ Over-run)?
Is there ANY sound of "Exhaust Spit" in the area of Headers or beneath vehicle?
Any prior instances of "Misfire" on Bank 2?

The following were the suggested steps in Fault Info Sheet, "Service Notes". Any sign of physical damage or discoloration (from excessive heat)?
If you have a USB Endoscope (~ $20 US), you can remove pre-cat O2 Sensor & view Cat, aimed BACK into Cat:

1. Visual inspection of catalytic converter
- Physical damage?
- Is extreme discoloration present on the converter?
(gentle reddish-blue hue is normal, especially after high-speed highway operation).
2. Leak check embracing entire exhaust system
Seal leaks and conduct road test
3. Remove O2 sensors and visually inspect for particles,
extreme discoloration, catalytic converter residue
Visual inspection through sensor holes in catalyst matrix as
indicated.
4. If O2 sensor fault is suspected: Consider replacing O2 sensor
(Did any known sensor faults or malfunctions occur prior to the catalyst fault code being registered?)
George

[PhaseP]

Exhaust leaks will show up as black soot around the area that leaks. A visual inspection for such will rule out exhaust leak as culprit.
The connection of the mid-pipe to the manifold just after secondary 02 sensors tend to rust and start leaking by time.