I have buddy that just purchased a 2001 740iL and has a check engine light.

We plugged in my peake tool and on 2 seperate occasions he is getting:

Secondary Air System - Cyl 1-4
Knock Sensor - Cyl 1-2
Knock Sensor - Cyl 3-4
Knock Sensor - Cyl 5-6
Knock Sensor - Cyl 7-8

Any ideas what would cause these - and corrective action?

Those sensors can fail with age...gonna cost you 50-100$ each..never replaced em though, you'll need to ask one of the more seasoned bmw diy'ers on the board.....tell your friend not to put cheap gas in his car----ever:nono ...oh, i almost forgot..tell him to run some good injector cleaner the next couple of times he fills up...do a quick search on the forum for "ejector cleaner" and you'll get a pretty recent thread about which brands 7 owners prefer.

Those sensors can fail with age...gonna cost you 50-100$ each..never replaced em though, you'll need to ask one of the more seasoned bmw diy'ers on the board.....tell your friend not to put cheap gas in his car----ever:nono

+1 I agree, the usual difference between regular and premium is about twenty cents. If you do the math you will notice that the savings to repair ratio isn't worth it.

The E38 has a 22.5 gallon tank and if you had to fill it up from completely empty once a week for a year straight the difference would be about $234 more. If you really have to worry about $4.50 a week then maybe this car wasn't the optimal choice but to each their own.

Thanks tons guys, this is the best BMW board and all the people here are so great! I will pass this along!