With permanent fault codes 2B71 and 2B72 I removed and disassembled the manifold & motor to better understand what might be a cause of failures. I do understand the manifold is not intended to be serviced, but I was curious. After disassembly I found the drum had significant carbon deposits causing too much friction for it to spin easily. I thought I found the issue. After thoroughly cleaning the entire assembly I reassembled carefully making sure to reseal. Although there was still a rubbing sound it had been greatly reduced.
The motor tested at 2.8 ohm (spec 2-8 ohm) and actuated quickly and positively with 12 V applied. I felt good with my repair.
The engine was loaded with carbon and needed valve seals amongst other things, so I pulled it to do a complete re-fresh. Upon restart I found I had the same faults. After researching I found that max voltage supplied to the motor from the dme is 5v and often with less. I made a big mistake by assuming it was 12v. When I applied 5v to the motor (mounted on the intake) it rotated the barrel, but very slowly, and pulling higher amps then I thought it should. Bench testing the motor went better obviously without load and seemed fine. Curious, I removed the throttle body and tried to spin the barrel with my fingers, barely could move it, but with a little help from a ratchet it moved with little effort.
With that long back story, my questions are simple.
1- What is the minimum voltage required to actuate the drum?
2- Is my assessment of the motor correct that it tests within spec?
Thanks for reading and leaving any words of wisdom.
Never had to pull it apart - but I would guess that there must be some kind of feedback to signal the error codes - is there a sensor built into the motor assembly? Or, is the feedback the current taken by the motor as is used in some other systems?
Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i
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