in a W124 its near the accelerator pedal in a LHD car, the W140 should be similar as I dont think MB would route it over or under the transmission - the NSS on all older transmissions is at the left side of the transmission.

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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)