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Old 01-28-2005, 09:11 AM
al_r al_r is offline
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Location: Chicagoland
 
Join Date: Jan 2005
Posts: 2
Mein Auto: '96 328i
That is your secondary air pump, 'injects' fresh air into the exhaust manifold at start up time till the ECU shuts it off - strictly emissions related. If the pump fails, you'll get a CEL/code indicating 'not enough volume' in the front or rear engine banks.
If you decide to replace it, also replace the valve it feeds on the exhaust manifold.
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