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Old 05-01-2013, 02:06 PM
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540iman 540iman is offline
resident, old fart
Location: N.W. Indiana
Join Date: Sep 2008
Posts: 1,873
Mein Auto: 2002 540i sport
SAP system sends injected air from the pump, through the valve, air into both heads (on a 540). O2 must see an appropriate swing to a leaner condition when pump is running. I did not mean to suggest that the bank that is not working has a bad 02 sensor, but if the pump were not running at all, you usually get an error on both banks. Swapping O2 from side to other side would just rule out sensor that does not need to be bad as in "not functioning", but may just not send a signal to the DME that it is seeing a proper lean swing while pump is running.
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