e39 530i catalytic converter

[Mike WW]

A year and a half ago my M54 lit up the SES warning and INPA returned fault code EA 234 P0430 - bank 2 cat low efficiency. I could clear the fault and drive a couple of weeks before it returned, or a day. Often INPA would report the fault as not currently present, but of course the SES light would stay lit.

Mostly because it was due (but also trying to deceive myself into believing it might help) I replaced all 4 O2 sensors with Bosch and spark plugs with NGK over several weeks. I also repaired a slight leak on bank 2 at the gasketed flange. All the while searching for replacement cat alternatives and agonizing over which option to take. And dreading the R&R job to come.

But, miracle of miracles the SES light has stayed off for the last year plus and 20k miles. Might be worth a try for you.

My E36 coded for cat efficiency just after I bought it. Same thing, I replaced all 4 sensors, M52 in this case, but same as early E39. That code has never come back in over 100K.

[ross1]

Been there. This happened to my '03 530i.

Don't waste time or money replacing O2 sensors or installing spark plug extenders. They won't work. Cat diagnostics are very thoroughly engineered and not easily fooled anymore. Cats are an integral part of the ULEV standard (Ultra Low Emission Vehicle), and '01-'03 E39s qualify. Your car will get lousy gas mileage, have stinky exhaust, and throw misfire codes without working cats. And of course, you'll fail a state inspection..which makes your car illegal to drive.

You have no choice but to replace them.

Do not touch aftermarket cats for your I6 engine. You'll need OEM cats only! Only OEM has the precious metal content required to satisfy the DME and achieve the required level of emission reduction. Used OEM cats, if you can find them legally, are not worth the trouble and are likely to be ruined or tainted. They will not fool the DME. Ask me how I know.

If I recall, OEM cats are about $3000/pair, plus about $800 labor. So it should come in around $4K total.

Only you can decide if that's worth it.

Likely, why? Are you saying most of the cats in service are faulty?
No reason to dismiss used cats, sorry your experience was bad.
OE cats are VERY robust and given a healthy, properly running engine last hundreds of thousands of miles. Lots of dead or dying E39s willing to give up perfectly usable cats.
The laws restricting sale are absurd. If used ones can serve the purpose why not?
There is a good reason OE cats are often worth more in scrap than the price of new aftermarket ones.

[Frankie]

Sorry if I'm generating "negative vibes". My intention is to separate wishful thinking from real-world solutions. Every owner of an older car will eventually face repair costs exceeding the car's value. V8 owners know this with TCGs. I6 owners face it with new cats. And the OEM route should cost closer to $3K, not $4-$5K.

..flash your DME to an EU2 tune..

This sounds like an ideal solution. But for me, it raises more questions than it answers. It boils down to: do you trust the coding shaman and his engineering skills?

It's not enough to simply disable the CHECK ENGINE light. Engine readiness monitors must also report READY status. (See link3 below where this didn't happen.) If turning OFF the O2 sensors entirely, what substitute signals are sent to the DME? When my cats failed, my car ran like crap (misfire codes, poor gas mileage, stinky exhaust). This indicates that O2 sensor input is integral to DME calculations. So these conditions will continue unless a non-trivial engineering effort is made to generate default engine mapping. While I have no experience with engine tuning products, it seems one should tread carefully. They are also illegal.

[RE: spacers with cat material] [link1] [link2] didn’t exist a few years ago....

...X5M with catless downpipes and his monitors are set and ready. [link3]

This is indeed interesting Ryan.

Like you, this product didn't exist when I was dealing with cat trouble. I think it shows the inadequacy of using simple spacers. I tried Dorman spark plug "non-foulers" as spacers and the CEL came right back. The X5M owner in link3 has barely been using his cat-enriched spacers for a week, so it's impossible to say whether these products constitute long-term solutions.

Note "Big Daddies Garage" says:

Manufactured and Sold Expressly for Non-Road Vehicles Used Solely for Competition...
Not sold For Use On Production Street Vehicles ("on road" or "on highway" vehicles)...
...Do Not Use To Remove Cel Caused By Faulty Catalytic Converter!

And "Fabspeed" says:

For off road competition use only, not to be use on public roads or highways...
There is no guarantee this will prevent a CEL from triggering...

If these legalities aren't disconcerning, it *looks* like low hanging fruit.

I replaced all 4 O2 sensors with Bosch and spark plugs with NGK...the SES light has stayed off for the last year plus and 20k miles.

That's great! I wish it worked for me (I replaced only rear sensors).

No reason to dismiss used cats...

Yes there is. There's a pattern of failure with cats on E39 facelift cars ('01-'03). I noted this in Internet searches. I purchased used cats only to see them promptly fail. I can't begin to tell you how angry I was. DO NOT TRY THIS FOOLISH GAMBLE.

[demetk]

I bought a reflashed DME with EWS and SAP delete for $160 and the car passed all emissions tests in CT. I would say it's a viable and inexpensive option.

[timcotom]

Well guys, thanks for all of the information. At least now I have a direction, or several actually to consider. As some of you were asking, the car has 170,000 miles. The CE light stays on most of the time, but noticed the light off for a couple of weeks and then pops back on whenever it feels like it. I love the car and would like to keep it but its hard for me to justify paying more on a repair than the car is worth. I guess I will have to bite the bullet and get it fixed or spend $$$$on a new one. Thanks again all

[rdl]

Well guys, thanks for all of the information. At least now I have a direction, or several actually to consider. As some of you were asking, the car has 170,000 miles. The CE light stays on most of the time, but noticed the light off for a couple of weeks and then pops back on whenever it feels like it. I love the car and would like to keep it but its hard for me to justify paying more on a repair than the car is worth. I guess I will have to bite the bullet and get it fixed or spend $$$$on a new one. Thanks again all

Your "self healing" cats that then revert to low efficiency status mirrors my symptoms last year. My odometer was at ~190k miles, also similar to yours. More reason to think that your cats aren't hopelessly toasted and that O2 sensors & plugs might do the trick.

Regards repair costs. I went through the same thought process you describe. In the end I decided that the correct questions was, "how much would a car that satisfied me as much as my E39 cost me compared to the cost of repairing the catalytic converters."

Important though, I've maintained the car myself for 10 years and had confidence I wasn't throwing money into a bottomless pit. Further, I believed that any equivalent car that I could buy for the cost of new cats would not be as well maintained as mine. So there would almost certainly be additional costs to a replacement to get to an "apples to apples" comparison. Comparing repair cost to the wholesale value would be an "apples to oranges" comparison.

Anyway, I know it's a difficult decision. Good luck and best wishes with what you decide.