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2006 BMW 325i electric water pump
Posted to Technical Theory Forum on 12/20/2012 6 Replies

[2006 BMW 325i, Engine/Propulsion Waveform] [2006 BMW 325i, Engine/Propulsion Waveform] [2006 BMW 325i, Engine/Propulsion Waveform] Hey everyone. I had a 2006 BMW 325i come in with a code 2E81 "Electric water pump, speed difference". These electric water pumps are a common failure and we quoted the job to the customer who said it will have to wait until after christmas. Hopefully this thing will come back for the new pump and I can get a known good wave of a new pump, but until then I wanted to share these waveforms and see if anyone had any inputs on what was happening here. I amp clamped the power supply to this pump and activated it with a scan tool, expecting to see a 6 or 8 commutator waveform that I could calculate the rpm's of. Instead, I got a waveform with ramps that look more like injector ramps than commutator humps, and instead of the normal in rush of amperage that we see on a commutator pump, I had a wave that started out flatline and slowly grew in amplitude until it peaked at about 16-18A. The other thing that really bothered me was that after every other ramp, the wave dropped into negative amperage, as much as -8A in one capture. I quickly removed my amp clamp from the wire and re-zeroed it with no change in the waveform at all.

So, if there is anyone farmiliar with BMW's that has some input here, that would be great. What are the internals of this pump like? How does it work? Is this waveform good, bad, or inconclusive? Thanks for any help guysw.

Mike Harlan
Harlan Automotive, Inc.
Murray, Kentucky, USA

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car Vehicle Data

2006 BMW 325i 3.0L

Engine3.0 L
Trans6-speed Automatic (Electronic)