PACIFICMAN

Hello all, after the coil replacement My GLK runs great, strong with no change in MPG, etc. However shortly after the repair I got CEL and stored code PO 430- "The P0430 code stands for “Catalyst System Efficiency Below Threshold (Bank 2).” This trouble code is triggered when the computer detects a problem with the catalytic converter mounted near engine bank 2." There is no discernible problem withe engine, "rich" smell or the like. The code clears and stays gone for a day or two then throws again.
I presume the brief running, on Cylinder Bank 1, only while moving and jockeying the car around during the diagnosis and work, no more than 10 minutes running at low revs, dumped unburned fuel from Bank 2 into the cold exhaust and cold Cat. Perhaps "glazing" the Cat or otherwise corrupting it? Reducing its efficiency.
Please Share any thoughts experiences and possible fixes / addresses of this issue. Obviously I'd like avoid replacing the Cat, costly rip off in CA, if there is a way to rehabilitate the unit. I have seen various products that "clean" them, anyone have experience with them? Or any other thought or suggestions in this regard.

​​​​​​​Thanks In Advance!

Silver Shadow

There are many things which will trigger a PO430 code. Exhaust leak, oxygen sensor, cat problem and many more. In my lifetime only once has it meant a bad catalytic convertor.

Mmr1

Is it highway driven , it should be and maybe a cleaner could help , you mention that it’s running better , did you do the plugs and what was their conditions ?
I would try an additive cleaner and highway drive it high speed for as long as you can , but check other things as others have said , yes you need to heat the system up . I’m worried about mine , since I drive city . So many things to worry about . Direct injection fouling , catalytic converter ,

PACIFICMAN

Thanks for the input so far! I have discerned no exhaust leaks, no 02 sensor codes and the plugs were changed 30-35k ago and looked NEW when I removed them.
The car was barely running with the blown coil and dead short that led to coil replacement, Cylinder 5, Bank 2 and run for maybe 10 minute total while positioning it for the work. Since the fix the car runs just as before with or without the CEL and code being present or not, I can clear them but they return 30-100 miles later. Since the repair the driving has been almost all High speed highway, 300 mile R/T with a bit of around town. I'm about to do the same blast into LAX, park for a few days and blast back. I'm going to clear code and add some product, TBD, before I leave. Hopefully I can report some positive effect when I return...

NYCGLK

Could be bad 02 sensor....cat efficiency is determined by downstream O2 sensors.

habbyguy

I'd also suspect that the misfire could have "coated" the cat's elements with grunge, and that a bottle of "cat cleaner" and/or a nice, long, high-speed highway run might clear things up ("but really, officer, I was just cleaning out my cat, not trying to do 105mph in a 55...). Could be unrelated to the misfire, or like NYCGLK suggested, a bad O2 sensor (I consider them suspect after 100,000 miles).

PACIFICMAN

Hello All, Thread revive here. After 3 fuel Cat cleaner treatments and the associated prolonged high speed driving the Cat CEL stayed off for longer periods, up to 200 miles, however the frequency fell back down to 20- 50 mile intervals. I had decided to continue driving the car as the MPG and performance were not diminished at all, as far I could tell other than the "rich" exhaust smell reminiscent of my '69 GTX. Anyway, the situation has been moved back to priority by the CA DMV, I must SMOG the car this re registration cycle(every 2 years) So... Try as I might I cannot find the rear sensor oxygen sensors while inspecting under the rear of the car or find a 2014 GLK parts diagram showing the rear left oxygen sensor online. I assume this is the component reading the Cat output and throwing the P430 code.

My question: Where is it? Is my assumption correct re; code? Any other insight into this issue that may help my efforts?

I'm prepared to replace the Cat but want to bird dog all the options before I do. Thanks in advance for any and all input.

calder-cay

Although for a 2011 4Matic, might help.

Go to the 5:30 mark for the two sensor locations

John CC

The rear sensor should be right after the converter outlet.

P0430 is set when the signal from the downstream sensor follows the upstream sensor. The PCM will vary the mixture causing the upstream reading to oscillate. The converter should even the oscillations out. If you have a scanner that can read the sensors, take a look at the two outputs. If the output tracks the input then the converter isn't converting.

One cause, already mentioned, is if there is an exhaust leak. Often it is a flex coupling. The leak allows fresh air reversion.

Sometimes you can trick it by putting a spark plug "anti-fowler" on the downstream sensor. The theory is it isolates the sensor form the rapid changes.

PACIFICMAN

So, firstly Thanks to all who weighed non my last 2 threads. I seem to have found resolution on the Cat issue by, after my amateur diagnosis' and )2 sensor replacement and a Pro diagnosis I replaced it as SMOG check loomed and lo and behold it passed. Happy, but expensive, journey...

On the coil front I followed through with the replacement of the remaining 4, good preventive, I think. However on the rear most, driver side, the most difficult one this time and during the spark plug change a year or so ago. I used the ECU and bracket removal as opposed plenum removal and did in fact break the lead this time... I initially freaked out but once I calmed down purchased a Lisle 52990 Spark Plug Plier. inexpensive($15) and available at my local O'Reilly. It worked Beautifully even in the very confined space available, Strong recommend. Moving forward I'll use to safeguard the leads on future work.

calder-cay

Its 69°F and sunny here in south-central Texas, so a great time to sit, gaze out into the pastures, and read some Internet stuff

It's good to read you got everything squared away without dumping a bunch of cash at a shop!

And thanks for coming back out here and letting everyone know the outcome - always good feedback for folks.

And yea, I have spark plug pliers sitting in the toolbox for those occasions requiring it. I think I had to use those on my wife's E320 ... though I bought those pliers even years before for other vehicles I've had.

Anyway, great your back on track!

PACIFICMAN

Thanks Calder.