Not to long ago my Check Engine light bliped on while driving home one day. I drive a 2004 BMW 325i and my first thought was “oh great, there goes a grand”. After running to my local Autozone they told me the ODB-II Trouble Code was P0174 which translates into System Too Lean (Bank 2).

After a bit of research this error basically means that an oxygen sensor in bank 2 detected a lean condition (too much oxygen in the exhaust). I did notice that while driving the car did lack the power it seemed to have before the light came on. I’ve also read that other potintial symptoms can be detonation (spark knock), and/or a hesitation/surge on acceleration.

The upside was that the light didn’t indicate my engine was about to die. The causes of a P0174 could be one or more of the following:

• The MAF (Mass Air Flow) Sensor is dirty or faulty.
• There could be a vacuum leak downstream of the MAF sensor.

All of the BMW forum contributors seem to discount a faulty MAF. Besides a replacement is around $60 - $100. Many of the 2004 BMW 235i’s seem to have cracked intake tubing, so I started to dig around under the hood. At first glimpse I couldn’t find any cracks or leaks downstream of the MAF. The next place to check was all the tubes that branch off of the main intake. Sure enough, a small line was cracked and brittle, so much so that it broke as soon as I attempted to inspect it.

To fix my issue, I was able to remove the rest of the broken tube with a new section of fuel line I already had laying around. Just make sure the replacement tubing can withstand heat (it is under the hood next to the engine after all). The next step was to clear the error code to verify my fix worked. I drove back over to Autozone and had them clear out the error messages. So far, so good.

I figure I was lucky and my fix was easy. Based on what I’ve read, other possible solutions are:

• Cleaning the MAF sensor. Just make sure you consult your service manual for it’s location if you need help. I find it’s best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it’s dry before reinstalling.
• Check for a dirty fuel filter and proper fuel pressure.

So, if you get the P0174 ODB-II Trouble code, you need not fear. The fix might be relatively cheep and easy.