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Old 03-10-2011, 10:26 AM
clarkgd clarkgd is offline
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Location: Ottawa Canada
Join Date: Oct 2010
Posts: 24
Mein Auto: BMW 335d
Low Mileage DEF Warning

My occurrance happened at 9300 KM when the No Start in 1600KMs came on. Initial diagnosis was that Active Tank was low and Passive tank was 100%. The active tank was filled under warranty and appointment made to diagnose the problem. At the next appointment the dealer tech spent 5 hrs conducting testing on pump according to toubleshooting procedures. Pump would run for 30 secs and then shut down. Pump replaced with same result. Found problem to be crystallized blockage of vent tube. Blockage cleared and pump ran to fill active tank.
Technician is not a believer in the troubleshooting procedure any longer.
I don't know where this vent tube comes from or goes too but I suspect it likely links the two tanks and if blocked then the pump will not pump up to pressurize the active tank. Without the pump no refill of the active tank.
Seems to definately be a design issue that these smart German engineers should be able to solve and as a result is a warrenty item and each case needs to be fixed and DEF added at BMW expense. Without the blockage, I would have easily had enough DEF to last to the first yearly oil change at double the mileage when I got the warning based on individual tank capacities mentioned elsewhere on the board.
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