Need help troubleshooting a problem I've been having with my E39.
The secondary air pump, the diverter valve w/gasket were replaced less
than 6 months ago. The #117 MIDI 50Amp fuse was blown and replaced as
well. Last March noticed a Hoover sound coming out of the SAP area for
about 10 min. After that incident the SAP stopped working and I got
the P1423 code. I thought that the fuse blew again and because it’s
such a pain in the neck to replace it I didn’t do anything about until
last week.
Last weekend I opened up the fuse panel under the passenger seat to
check the fuse and it checked out ok. Next, removed the pump and it
was dead. It smelled like it was burned too.
From the Bentley diagram it appears that the ECU controls the SAP
circuit through a relay in the ECU compartment. The pump should be on
for 1-2 min when ambient temp drops below 51F. What would cause the
pump operate for more than 10 min and, as result, burn it? Sticky
relay contacts? Bad ECU? Leaky vacuum hose somewhere?
Any comments would be appreciated.

- Vadim

US Spec '99 528i 5 speed