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Old 10-27-2009, 06:50 PM   #1
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Join Date: Oct 2009
Location: Denver, CO
Posts: 10
My Ride: 2000 330xi
Riddle with 3 SES codes...

Help me solve this problem. My SES light came on sunday, so I dropped by autozone to see what was up. They were as follows:

P0155 O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
P0171 System too Lean (Bank 1)
P0174 System too Lean (Bank 2)

I have had the P0155 go off before and was going to replace the O2 sensor last winter but the light went off after a couple of days and I just wanted to wait till it died completely. I recently (a couple of weeks ago) changed my air filter and one thing I noticed when I looked under the hood after the SES went off last sunday was that the MAF connector (electrical coming in) was loose, but not fully disconnected. I reconnected it. So what I'm wondering is if the SES was due to that, or if the P0155 could be causing both the P0171 and the P0174. Not really familiar with what Bank 1 vs Bank 2 mean (guessing banks of cylinders?) and the O2 sensor code is only coming up for bank 2, while the lean system is coming up for both banks. Could any of this be due to improper air filter replacement? Everything looked good when I finished. Could it be due to a leak after the MAF, although not sure why the O2 sensor error would come up simultaneously if this was the case. Does the MAF need to be cleaned? I am driving a 2001 e46 330xi, right now I am getting 25 mpg and it has actually gone up (I think it was around 24 mpg) since I changed the air filter. My girl swears that she can smell burningish smell coming through the vents when we are idling, and I can sometimes smell it a bit when I open the hood, but it isn't too strong. I recently topped off the coolant, which was very low, I have replaced a cracked expansion tank a few years back due to a faulty coolant pump and clogged radiator hoses, and my engine briefly overheated.

Sorry if I gave TMI, but I just wanted to be thorough. Please help, I have to keep driving to work and would like to figure out what to fix asap.

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Old 12-17-2009, 10:59 PM   #2
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Join Date: Feb 2006
Location: Lexington KY
Posts: 172
My Ride: 330CI
Same codes here...any answers?
K2Elmore is offline   Reply With Quote

p0155, p0171, p0174

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