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Old 05-01-2013, 08:53 AM
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540iman 540iman is offline
resident, old fart
Location: N.W. Indiana
Join Date: Sep 2008
Posts: 1,874
Mein Auto: 2002 540i sport
Since you don't have both banks failing, suggests carbon build up in one head, bad O2 sensor (1) on bank 2 side, possibly it is a very small but plausible to DME low flow rate just to one side due to a loss of total air volume which could include valve, plumbing, and or weak pump. However, if I look at error code literally, it appears to be not enough air flow making it through just one head which could be CBU issue or piping from valve to heads leaking or just one oxygen sensor which is greedy and wants even more exhaust dilution. Would be interesting to know if it were possible to send the output of bank one O2 sensor only to both inputs of O2 sensors at DME. Could cause drivability issues worse than stupid SES light due to emission issue. There are software solution from PowerChips, but expensive. You might try swapping O2 sensors first from side to side and see if error follows O2 sensor or stays with bank #2.
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