The manual tells that you should be seeing about 3 volts at idle speed - 1.9 is a bit low, have you tried cleaning out the sensor - its on the transmission bellhousing.

btw is your tach inoperative?

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)