P0171 and P0175

[Anatoly]

Hey guys, quick question. My car keeps throwing this 2 codes, P0171 Powertrain System Too Lean (Bank1) and P0175 Powertrain System Too Rich (Bank2). Car: 2001 BMW 530i, I just got it about 4 weeks ago.
So far:
MAF sensor has been replaced
Intake Boot has also been replaced
O2 sensors replaced
My mechanic thinks it's my engine harness, because I guess the previous owner who was an idiot left everything hanging and when he was replacing the O2 sensors he had to "fix" part of the harness because it got burnt on the exhaust, but I think it wouldn't throw this codes for an engine harness though?
Car runs fine. I'm thinking I have a vacuum leak somewhere, but vacuum leak wouldn't explain the "system too rich".
I'm puzzled. Anyone help please?

[auaq]

A couple of basic checks that I would do:



I would inspect the wires first since you mention of previous owner's negligence.
Check spark plugs and replace them if they're old and worn out.
Do a smoke test to determine whether you truly have a vacuum leak or not.
Check all other and random vacuum rubber hoses/lines to make sure they are not brittle or have cracks in 'em causing lean conditions. Replace them if necessary.

[snoddy]

Definitely agree with auaq. Did you replace the MAF with an OEM Bosch MAF? I once replaced my MAF with an aftermarket version that was significantly cheaper. Won't make that mistake again.

[JimLev]

Won't an i6 throw the lean and rich codes if the pre CAT sensors get plugged into the wrong connectors?
Front sensor to the rear connector and rear sensor connected to the front socket??

[Anatoly]

So quick update. Did a smoke test today, found that the valve cover is cracked. Got a new one. So far, I have 1 code "pending" which is P0171 (system too lean bank 1), we'll see if the other one will pop up or not.

[auaq]

That can definitely cause the vacuum leak and turn on the CEL with that code. Hopefully, after you have replaced the valve cover the code will go away.

[Anatoly]

Well, both of the codes came back. I'm going to switch the O2 connectors and see if may be they were connected wrong

[Anatoly]

Switched the o2 sensor connectors, car ran like sh*t, so they were connected right. I'm seriously confused. I did replaced the MAF with eBay one, but I dont think it'll make it throw this codes.

[syphilouis]

How's your disa valve gasket? I had been throwing similar codes and I replaced mine and so far hasn't thrown a code. Been almost 2 weeks and I drove from tucson to Phoenix and back today and still nothing.

[JimLev]

Did you reset the adaptations after swapping the connectors?

[danb1979]

As above and check for CCV issues and DISA issues also

However, make sure that the intake boots are all put together and that the MAF's properly plugged in. This is easy to miss and as I had with my previous E38 (728i); I'd replaced the intake boot (both parts) and hadn't fastened them together tight enough and they were drawing in extra air and it was throwing the codes!

[Anatoly]

Did you reset the adaptations after swapping the connectors?

What's the process?

- - - Updated - - -


As above and check for CCV issues and DISA issues also

However, make sure that the intake boots are all put together and that the MAF's properly plugged in. This is easy to miss and as I had with my previous E38 (728i); I'd replaced the intake boot (both parts) and hadn't fastened them together tight enough and they were drawing in extra air and it was throwing the codes!

Checked the boot, MAF is also plugged in. I'm thinking, could it be that I bought MAF from eBay? The cheap one?

Another thing I should mention, with my old MAF I would throw a code P0102 Mass or Volume Air Flow Circuit Low Input, so that what made me believed my MAF was dead.

Car runs fine, idles smooth, this codes are just really annoying.

- - - Updated - - -

Well, the car threw a 3rd code today, P1500 Idle Speed Control Valve Stuck Open. Had the EML and DSC lights on. Stopped the car, shut it off, turned it back on, the EML and DSC lights went away ...
Anyone has any idea what could be wrong with this POS?

[Anatoly]

Update, looks like the problem was my MAF. I used one of those ebay ones, well, didn't know that they were sh*t.
Changed my MAF back to the old one (the one I thought was defective), it's all good now.
Looks like the main problem was multiple vacuum leaks, and when I fixed those and changed the maf it started freaking out.
All good now.
Thanks for the help guys.

[danb1979]

^^

Easily done!

Glad it's all sorted! :)

[gmak]

Update, looks like the problem was my MAF. I used one of those ebay ones, well, didn't know that they were sh*t.
Changed my MAF back to the old one (the one I thought was defective), it's all good now.
Looks like the main problem was multiple vacuum leaks, and when I fixed those and changed the map it started freaking out.
All good now.
Thanks for the help guys.


IN the past, I replaced my 528i MAF with a VDO SIemens one shipped from Germany. I got a CEL after that. I didn't clue in and finally took the car to an indy to troubleshoot. They said it was the MAF. I had to send it back in order to get a new one. When I put the old one back in for the interim, the CEL went away. The indy said that there are a lot of "name" parts - even from the mfg;er so you know they're not knock-offs - that aren't up to snuff and cause problems.

[auaq]

Glad it's fixed now.

[Anatoly]

And the codes are back now ... Seems like it's throwing the codes when you are in heavy stop & go traffic, when the car gets hotter. I'm at loss, been chasing this for a while now.