I always assumed it was because the coolant flow through the heater core didn't have a lot of "push" from the waterpump and this pump helps supplement.
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'09 HP2S, '12 R12GSA, '00 Black 323iT, '02 Alpine 325iT (Track Wagon), '02 Alpine 330iT
Instagram @HillPerformanceBimmers
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Just adding to this for posterity.
I have swapped in a non-M facelift IHKA and also deleted the AUX water pump. ZUSATZWASSERPUMPE was set to 'nicht_aktiv', but I was still left with DTC 29 "Kommunikation mit dem Zuheizer". ISTA flagged this up as something like "No communication to auxiliary water pump" or something along the lines.
Change ZUHEIZER from 'k_bus' to 'konventionell' to clear.Comment
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