P0171 and P0175 | e46 M3

[tomandhisjones]

So, I recently purchased an e46 M3 from Chicago (I'm in Kansas City). It arrives off the truck, and is immediately running rough. I get to the house and run a scan to find codes P0171 and P0174. I checked for vacuum leaks, replaced the fuel filter, and finally replaced the MAF sensor. After replacing the MAF, I started getting codes P0171 and P0175, one rich bank and one lean bank. After hours of research, I decided it was the upstream O2 sensors. Had those replaced today, and I'm still seeing the same codes and rough idle. Any ideas what could be going on? I'm stumped at this point.

[328 Power 04]

Any chance of them (upstream O2) being swapped connectors?

[tomandhisjones]

Took a look, and everything is wired up correctly.

Took it to the local dealership, and they said my cats were clogged (and ask $5k to replace). Went to an Indy shop and they cleaned out my cats, and that didn't resolve the problem. Got another new MAF, just to make sure I didn't get a defective one.

Also had a smoke test done, and everything was fine there.

[MIKYZZ4]

Make sure any type of electronic sensor you replace is only OE or OEM,anything else will have you chasing your tail, due to electronic gremlins and anomalies,I can't stress this enough, seen too much time wasted-too many times before.- - - Updated - - -Stay away from that dealership, if that's their diagnosis.(cats)

[MIKYZZ4]

You have a lean fuel mixture condition, and you seem to have checked the usual suspects.
Try checking for proper fuel pressure at the rail. Also where is your FPR located-rail or filter?

[shadowpuck]

how does one "clean out" cats.....call me suspicious on that point.

was a back pressure test performed?

i see you are in the KC area - what shop(s) are you dealing with? there are a few places i can recommend without hesitation.

[bmwdirtracer]

cat shampoo.png


I think you need to hook a scanner up to watch live data, and unplug the primary bank 1 sensor, and see whether the correct sensor stops working. In other words, I agree with the likelihood that your sensors are swapped.

If they are not swapped, then you should send your injectors off to RC Engineering, and have them ultrasonically cleaned and computer tested.

You have codes for one bank lean, and the other rich; there's nothing which indicates that you need catalysts.

[dworthy]

+1 you need to see live data

Just having the oil cap loose can cause those 2 codes funny enough.

[tomandhisjones]

how does one "clean out" cats.....call me suspicious on that point.

was a back pressure test performed?

i see you are in the KC area - what shop(s) are you dealing with? there are a few places i can recommend without hesitation.

I have a guy in midtown, who does not have a BMW specific shop, but is generally good for most things. Who would you recommend?

- - - Updated - - -

I'm going to check my ICV this evening. I found a few posts that say if it is stuck, it seems to give the same symptoms. Will also clean out my throttle bodies while I've got the intake manifold off.

[shadowpuck]

for an e46, in no particular order:
515 Motorsports in Liberty
KC Autosport in Shawnee
Santa Fe Garage in Independence
Auto Tech Service Center in Shawnee

[bmwdirtracer]

+1 !!!

Oh, dear me....PLEASE do NOT take an E46 M3 to a generic shop ! Follow shadowpuck's advice !

I think there's a good chance your sensor plugs are swapped. But do not even consider buying cats without a LOT more proof that they're bad. Hell, you don't even have cat efficiency codes!

Send those injectors off to RC engineering....that's $25 per injector, plus shipping...best bargain in the automotive world!

[dworthy]

Wait, what ICV? The S-54 doesn't have one that I know of, as it is a Individual Throttle Body motor where it gets all it's air from a plenum.

Unless you are close to 150k miles I would wonder about the cat's, and the oxygen sensors have a replacement mileage of 100k BTW. Also the spark plugs should be replaced every 60k too.

I would want to see something other than "P" codes for that car.


Thanks guys, I had to go out and check, for there is one.

[shadowpuck]

i agree - and wondered about the ICV too.

i'd much rather spend a diag fee (or two) confirming a very costly diagnosis.

and, sadly, anymore, i just assume any used car (especially a BMW) has had some nonsense/silliness done by the former owner(s) - be that cheap parts, half fixes, etc. i just assume i'll find them - i constantly find stuff when i help friends and club members do inspections on their recent purchases.

[328 Power 04]

The S54 does have an ICV, but I don't think it's related to your issues.

[MarcoZandrini]

Tom, here's the skinny. You have a high maintenance car. Unless you have a ton of $, I suggest you invest $ in some diagnostic tools. I have OBDFusion. It's a great product for diagnosing engine issues. It allows for data logging and exporting. It's available for both Apple (iOS) ($10) and android ($4) products. iOS needs a wifi communications interface, while android uses Bluetooth. Go to E46Fanatics and find threats on OBDFusion in which jfoj has commented. He's the guru.
There are many other great diagnostic tools out there. Search this forum. Btw, you've received some great advice from techs who know their stuff. Heed it.

[tomandhisjones]

Thanks Marco, I am definitely appreciative of all of the advice from everyone.

Do you know if OBDFusion picks up BMW specific codes like INPA/DIS?

[shadowpuck]

obdfusion is great for data logging and is affordable.
it's not going to read bmw manufacturer codes though.
carly will do this - but, i haven't had a chance to dig too deep into that program because i just use INPA most of the time.