Not your average SES P0171, P0174 error code...

[mika]

Originally Posted by adnoid

Funny - I just started to get these codes as well. 2002 3.0 with 202,000+ miles.

Last week I had a brief stumble in the morning, followed by the SES light on the drive to work. Other than the stumble the car drove just fine, with one significant difference - much BETTER gas mileage! I usually get around 19, I suddenly was getting 23+. When I was able to read the codes I got:

P0171 (System too lean, Bank 1)
P0174 (System too lean, Bank 2)
P0300 (Random/multiple misfire detected)
P1347 (Misfire cylinder #3 with fuel cutoff)
P1348 (Misfire cylinder #4 during start)
P1350 (Misfire cylinder #5 during start)

I noted them, cleared them & left the reader connected. The next day the SES returned with all the above codes and these:

P0302 (Cylinder #2 misfire)
P1083 (Fuel control mixture lean, Bank 1)
P1085 (Fuel control mixture lean, Bank 2)
P1342 (Misfire cylinder #1 during start)

I took it to my indie repair shop (good guys) and they replaced the pre-cat O2 sensors and the intake boot which had a crack in it. I could discern no difference in behavior of the car before or after the repair, but right after I picked it up my fuel consumption was back where I thought it should be. Then the next day I got the SES again with just P0171 and P0174, along with the reduced fuel consumption, albeit only up to about 21 MPG. I reset the codes again, and although the light has not come on again I can see P0171 and P0174 are pending.

What's interesting is that this began to happen immediately after I filled up at a station I don't usually go to, but I was low and running an unplanned errand. It was a Miristar and the pump said the fuel could contain up to 10% Ethanol - has anyone else experienced any such connection?

Still, the car runs great - fires right up without hesitation, not lacking power, smooth, and if not for the lights/codes and the increased mileage I'd have no idea anything was going on!

Thanks Adnoid - I had the same mix of codes (p0171 p0174 p0300 p1342 p1345 p1347 p1348 p1350 p1352) and knew it wasn't the Y duct (replaced last year). I pulled out my DISA Adjuster Flap and it looked just like you your photos.

[Greg]

I too have the codes P0171 & P0174 and failed my states emission test to renew my license plates. I just received the Air Mass Meter from Partsgeek.com ($314.95) cheapest I could find. Replaced it and used my ACTRON to read the codes. Same codes popping up. I went ahead and erased the codes and will drive for a week and see if they return. I have a 2001 4.4 with 87K miles. Never replaced the plugs, should I? I check for leaks around the air filter housing and the boot that attaches the Air Mass Meter and found no leaks. Any more helpful suggestions?

What is connected to the front bottom of the Air filter cover that has a hose connected to it?

[youry]

well, I wasn't that lucky this time.
adnoid....are the pre-cat O2 sensors the same as regular O2 sensors? I don't see any other type of sensor on realOEM other than the regular ones.

[Weasel]

As far as placement goes, pre-cat monitors the air/fuel mixture for running purposes, post-cat monitors the performance/efficiency of the catalyst as far as cleaning the exhaust.

You can see in the link it calls one "regulating" and one "monitoring".

RealOEM.COM * BMW E53 X5 3.0i LAMBDA PROBE FIXINGS

[youry]

I never knew there are 4 O2 sensors. To make sure I order the correct O2 sensor, the pre-cat is the one that connects to the manifold, right (number 1)?
thank you

[Whoopitupinmo]

I have had these 2 codes on SES for quite some time. Changed MAF to no avail. When in for service on other issues at BMW dealer, they tell me I have a coolant leak and valley pan needs replacement as well as valve gasket cover leaks that are causing my SES.

Does this sound right?

2001 X5 4.4i, 117000 miles
Plugs were replaced as well as hoses to oil seperator

[Weasel]

Originally Posted by youry

I never knew there are 4 O2 sensors. To make sure I order the correct O2 sensor, the pre-cat is the one that connects to the manifold, right (number 1)?
thank you

Yes, but there are 2 pre-cats. The one on the front manifold is bank 1 pre-cat sensor (cylinders 1-3) and the one on the rear manifold is bank 2 pre-cat sensor (cylinders 4-6).

[youry]

Originally Posted by weasel56

Yes, but there are 2 pre-cats. The one on the front manifold is bank 1 pre-cat sensor (cylinders 1-3) and the one on the rear manifold is bank 2 pre-cat sensor (cylinders 4-6).

I found the problem. I popped up the hood to see if there are any air leaks and I just realized the oil cap is missing. A few days ago I had to add some oil but I forgot about the cap. I will use some duct tape until I receive a new cap.
thanks for your time guys

[Greg]

OK, I just replaced my MAF yesterday after getting codes P0171 and P0174. Drove it today after resetting the computer. Drove around for about 1 hour came back home and tested it again. Horray no P0171 or P0174 codes. I now have codes P1159 and P1161 which basically is telling me my MAF is bad. Now what?

[Whoopitupinmo]

Same thing here. Maybe Weasal 56 will give us some input. This is really frustrating.