P0491 Emissions code. Need help!!

BimmerRob08 · 03-23-2018, 01:06 PM

Hey fella's,

So yesterday my '08 E92 M3 failed emissions for code P0491. My M3 is fitted with encore high-flow CAT's and DINAN Software Stage II. I moved to Nevada and used to live in New Mexico where my M3 would pass just fine with DINAN stage II and high flow CAT's. Never through this code before. Only has 78,000 miles and well taken care of. I have not yet gotten BMW here to diagnose it and looking to find answers first before I waste money at a dealership and get a run-around as I'm new to this area. One issue now is the BMW dealers in Las Vegas dropped DINAN and so I'm at a loss of who would be able to redownload it after working on the M3. Normally I had BMW handle it all but now that is going to be an issue I'm guessing.

My google search for this code for the E92 doesn't bring up much from others experiencing the code but points to a oxygen pump. What are your thoughts on this? Search brings up the fallowing from another posting. Most likely I can replace them easily but chasing a vacuum leak as we know can be a real pain in the ass. Any constructive suggestions are appreciated. Thanks!

1) Air pump failure
2) Check valve failure
3) Vacuum line failure
4) Vacuum pump failure

03-23-2018, 01:06 PM	#1
BimmerRob08 Lieutenant Colonel 253 Rep 1,527 Posts Drives: 2008 M3, Space Gray Join Date: Mar 2008 Location: KIKR (ABQ), NM iTrader: (0)	P0491 Emissions code. Need help!! Hey fella's, So yesterday my '08 E92 M3 failed emissions for code P0491. My M3 is fitted with encore high-flow CAT's and DINAN Software Stage II. I moved to Nevada and used to live in New Mexico where my M3 would pass just fine with DINAN stage II and high flow CAT's. Never through this code before. Only has 78,000 miles and well taken care of. I have not yet gotten BMW here to diagnose it and looking to find answers first before I waste money at a dealership and get a run-around as I'm new to this area. One issue now is the BMW dealers in Las Vegas dropped DINAN and so I'm at a loss of who would be able to redownload it after working on the M3. Normally I had BMW handle it all but now that is going to be an issue I'm guessing. My google search for this code for the E92 doesn't bring up much from others experiencing the code but points to a oxygen pump. What are your thoughts on this? Search brings up the fallowing from another posting. Most likely I can replace them easily but chasing a vacuum leak as we know can be a real pain in the ass. Any constructive suggestions are appreciated. Thanks! 1) Air pump failure 2) Check valve failure 3) Vacuum line failure 4) Vacuum pump failure
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