My scanner shows realtime pressure from the high pressure pump on wife's 50i and I think they use similar pump hardware.

My in tank pump on e53 just went kaput and of course the same basic pump supplies the high pressure pump so it is definitely tricky to figure out. I do not recall finding similar pressure for low pressure pump when scanning the 50i.

You can tap in under the seat how you describe to get a low pressure reading or depending on the age you can preemptively replace (do a little math they last 5-6000 hours on average).

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)