Engine/exhaust emission hi same problem with my 318ci coupe,few months ago the light showed up for few hours then went off. now few days ago came back on again,stayed for 2 days and now off again. just got the car read on the machine and there are2 faults, it may be the exhuast,so they got to check the exhaust system or it may be the 02orh2 cenre, cant remember what it is called. the light has now gone off,shall i bother getting it fixed, or may sell the car waiting for quote

I would first try to do a hard reset which means disconnecting your battery for 24 hours, that solves more problems than you would imagine.
Good luck.

Run a Diagnostic test on the vehicle computer,
code(s) stored in the vehicles PCM/ECM, will let us know more about the vehicles symptoms.
AutoZone will connect a scanner for free.
Post back with the codes

http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f80380329#hd1-1-28 Here is what is listed for problems,couldn't find codePO446,click on link to view.

I think we all just live in a world of automobiles,that have
too much high tech technology,when not so much is needed,
just to keep exhaust emissions at an acceptable level

At least you kept going back to the dealer & not keep driving
as most people do

You gave the dealer techs several chances at resolving the issues,
all be it, expensive, to say the least.

I don't see anything where you went wrong, or they let you down,
assuming your good to go & no more issues

I assume that the head gasket was something that only moved
& leaked internally under certain conditions & I don't know why or
when the ECU came up as a problem,they don't fail often

For the slow pick up of speed, change the EGR valve. A bad exhaust Gas Emissions valve will make it impossible to pick up speed or climb a hill of any kind. Fix the exhaust system leaks also, That could make the Oxygen sensor not work properly and cause the check engine light to come on. Once you've done all repairs, other than what I've told you, the light will not go out on it's own. You need to take it back to Auto Zone and have them turn it out electronically.

Sounds to me that the O2 sensors are sensing a problem with the emissions, or other emision controls have detected a problem that may not necessarily cause a driveability issue.

If you have emissions inspections in your area of the country, then I would have it repaired before the next inspection.

Have the OBD-II scanner check out the computer codes and descriptions by Autozone or Advance Auto Parts for free, or buy your own scanner for under $100 from Sears or Walmart.

Good luck on the repair.

Verify the O2 Sensors. Also make you do NOT use Regular gas, use high octane

its your secondary air pump. it turns on in the cold morning to inject more air into your exhaust, something about emission. its normal to be high pitched. once on my car it was way loud, i looked and the hose had disconnected. either way its normal if its not super loud. but if its everyone is looking at me loud then check for loose hoses!

the alarm is activating when he locks it and for some reason the key or fob isnt deactivating it..check the disarm switches in the door

this may be your egr valve, does it want to stall when its ticking over.