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Discussion Starter · #1 ·
I really hope any of you can help me now. Have had this problem to battle with in the past months now.
Problem is that the faulty codes "catalytic converter bank 1 & 2" comes up.
As previous read and discussed in threads here I have changed the lambda/CO2 sensors and the temperature sensors for the cats.
As I see it, It is unlikely both cats that not work. Anyhow I have had the cats checked and looked into them and everything seems good with them. They are in good condition.
I have also now changed the "air mass meters", do not know the right name in english, but the units measuring and setting the mix air/fuel.
But I still get the problem that the exhuast gas-values light turns on.

The other strange thing with this issue is that the light turns on after around 160 km (100 miles). That means that I read off the error codes and get the light turned off, then I can drive totally normal and after 100 miles it turns on again. So strange, tried it three times now and get the same result every time.

Should also be noted that before as after the lights turns on, the car goes great, there are nothing strange with how the car acts so it does not "feel" like problems.

Does anyone have further ideas or has been through the same story?

2006 m5 (55000miles)
 

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Discussion Starter · #3 ·
Hi,
The ionic box? What is that?
I have read on the forum, but that seems to do the unit control the engine? Just to be sure, I have no noticed problems with the engine. It seems to be with the exhaust gas values..?
But perhaps the ionic box affects that as well?
 

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Hi,
The ionic box? What is that?
I have read on the forum, but that seems to do the unit control the engine? Just to be sure, I have no noticed problems with the engine. It seems to be with the exhaust gas values..?
But perhaps the ionic box affects that as well?
The ionic control unit acts as a knock sensor on these cars. I would suggest you take the car to the dealer and have them diagnose the problem for you.
 

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I would be inclined to believe that it is in fact your cats. You have changed the 4 O2 sensors and the MAF sensors on both intakes all that remains would be the CATS. As far as the the miles driven between code clearing and emmisions light, that is normal. Whenever you clear the codes on an emmisions related fault the car has to be driven a number of miles before the code is thrown again. Most of the time (at least on cars I have repaired) that milage is between 70 and 100 miles. The ECM needs an certain amount of stored emmisions data before throwing the code, that data is captured in start cycles (30 cycles roughly) and miles driven. The only real way to solve this is to take the car to a dealer or Indy that can measure the oxgen values of the exhaust and then compair them to the BWM spec for the M5. Your ECM is still measuring a exhaust value that is over the max limit set by BMW. Cats loose effeciency over time, a visual inspection is not enough to determine catalytic effeciency. All a visual inspection will do is determine if the catalist materal has broken down and started to crack or worse had a hole burnt through it. Get them tested and I bet you find they need replaced.

Hope this helps....I learned all this the hard way on the exact same type of problem, however the car was a 04 Nissan. Both cars M5 and Nissan use OBDII as the operating system so they should be very similar in operation.

Good luck!
 

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Just had my 2 cats replaced. Pulled the two exact code; took it to dealer and they agreed the cats were gone after they pulled same code. $10k later (covered by BMW 8 year/80,000 mile warranty) I was back on the road. What's interesting is that I was averaging about 13mpg city and about 17 highway prior. After the replacement, I'm averaging 16 city / 20 highway. Not sure if the new cats make a differenceg, but not complaining.
 

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I also think it is your cats...when a car says catalyst efficiency below threshold there is pretty much nothing else it could be...but it's also a good idea to find out why they failed...
 

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Hi,

I have a similar story.
Does your car increase idle frequently at normal operating temp., like it does at cold start to heat the cats? Up to 900-1000rpm and change exhaust sound. Mine m6 had this problem when I bought, also check engine light was on. I have checked the error codes, and found that thermostat and water temp sensor were faulty. I replaced them along with the vanos solenoids (The test result was 0.45-0-50). Now no error codes and CEL does not illuminate. But the idle problem is still existing. It looks like the car is trying to heat up the cats. Two options wrong signal from the sensors or inefficient cats like 1hotm5 says. I was trying to figure out if it is catalytic converters that cause this problem, I found your thread.
If you have idle problems like me it seems like you have faulty cats. I will check the O2 and temp sensors at the exhaust. If they are ok too, I would conclude my problem as cats, too...

If it is the cats, the reason shoud be found.
My suggestions;
High oil consumption, (mine consume 1l/1000miles)
Faulty temp sensor (like mine)

any other suggestion will be appreciated, since I am also not 100% sure with my problem..

By the way this is my first post in this forum so hi to everyone who is reading.
 

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WoW,
I thought I was the only one but taking my car in found that one of the cats in my headers needs replacement.
I mean how does that happen at 15k miles - What **** has been put into these machines costing an arm and a leg that goes out at 15k miles.

Anyway,
BMW agrees for a replacement header and is fixing the problem, glad I was under warranty.
The funny thing is I was doing 14.5 highway\city combined not sure if that says anything but expecting a little more after the problem has been fixed.
 

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In the state of California if your vechile is under 70k miles or 7 years if any faults exist on your exhaust, from the cats on to the rear, your covered and the dealer should replace them. It's a state law. The rough idle on start up is normally caused tdue to your 10 individual throttle bodies trying too synchronize. It normally takes about 90 seconds. I have a 2006 m5 and my ses light has been coming on and off for about 2 years now. The only time I notice the car drives for a lengthy period of time without the ses light going on for the cats is when I gas up with chevron or shell. Any other gasoline sets it off, on that first tank. Then 2-3 tank cycles qith she von clears it up. I've had my cats removed and inspected and they are perfectly fine. A faulty bionic control unit would send your car into limp mode. I experienced this at 64000 miles. Out of warranty. Cost me $800 at the dealer ship to the fact indy shops couldn't figure it out. I currently have 172000 miles on my m5. Do not allow many of the horror stories here scare anyone off. A well maintained car will be a gem.
 

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I have been getting a soft code on my scanner cat passanger side runs hot today got service engine soon after driving in rain all day I guess my cat is gone will look tonight. I did replace my clutch in spring and find the seals on the exhaust pipes have leaks I put new donuts bolts don't go any tighter maybe I did something wrong. I wounded if the leaks could cause problems maybe I'm just hearing things?
 

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Im having similar issues...

I got 278A/P0430 and 2789/P0420 codes on my 06 M5 with the following results. 72kmi on the car.

Below is what I get when I run the Catalytic Converter Test in GT1, after car is at operating temp:

Diag Before Cats:
Bank 1 = 1.0
Bank 2 = 1.0
(Set point should be > .04) So, the above results indicate normal. I guess this indicates everything before the Cats is O.K?


Diag After Cats:
Overall = 2.0
Bank 1 = 1.6
Bank 2 = 2.5
(Set point should be < 1.1)
Software states " if > 1.5 = replace Cats." So, both Banks indicate above threshold value.

Repeated this test plenty of times on differs days with basically the same results.


I am interested in the De-Cat software is because I do have the Dinan Stage 1 software tune, K&N OEM air filters. Maybe the tune has something to do with it? I also am running 5w-30 (instead of 10W-60) which I read the excessive oil burn-off (because its a thinner oil) could be causing problems with the lambda values?

Im at my wits end. I've done a smoke test and I'm pretty confident I have no intake leaks anywhere. I have looked inside my Cats and didn't see anything cracked or broken, but I realize the values still point to bad Cats or two bad O2's? I really don't feel like spending millions of dollars replacing thats Cats.

Could someone please tell me more about De-cat software ??
 

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Catalytic converter bank 1&amp;2 problems

For what it is worth, here is an observation I made on my way to replacing one of my O2 sensors:

I had my CEL coming on only after long rides, say more than 60 miles without stopping. Typically, these kind of drives are somewhat spirited for me. On the 2nd drive cycle, I *always* got a light faithfully. I could adjust my watch on that moment! However, while normal commuting on backroads, doing 20 miles a drive cycle, I could go for *months*, never seeing a light!

O2 sensor diagnostics are always a bit mysterious, so went to clear the code and see if the car really means it. This went on for 2 years or so. Not a critical matter as the light stays off for months on end.

But a few months ago I decided to understand it and solve it. I decided not to clear the code for a while. I did this because ISTA/D then conveniently guides you to the O2 diagnostics you run. Laziness. Really. When I checked after a few days I got also the additional cat efficiency code for that side, like you do. I read up on some German documentation on the matter, which originated from BMW, and found evidence that this could happen after a while when the pre-cat sensor would be diagnosed bad and had set a code. Even though the cat may not be bad. The lambda software state machine works like this. Note that the lambda controller for bank 0 and 1 are fully independent.

I proceeded to replace just the pre-cat sensor on the driver side. Coincidentally, the passenger side sensor was replaced by the dealer 2 years back when I bought the car! The problem now seems gone: both the pre cat code popping up every now and then and the cat efficiency code. The wide band pre cat O2 sensors just wear out after 50k miles.

It may be worth it to replace both your pre-cat sensors. I know: This is a 400 dollar exercise (when you do it yourself) but I think it may clear you from this issue.

The 2 codes you report say in my manual for troubleshooting:

1. Check exhaust system for leaks

2. No faults related to oxygen sensor or fuel system or VANOS should be present

3. Conduct oxygen sensor test routines, even if no oxygen sensor fault is present.

4. Replace catalytic conveter near
engine

All of this matches my observations as well as yours.
 
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