So I had a defective K75 HES sensor plate from a 1987 model and decided to dissect it.  Here's what I found:


The wires exiting the Hall effect sensors is as expected in accordance with Honeywell documentation - Red=+, Black=-, Green=Signal

But the wires within the BMW cable don't conform to any reasonable standard - + = Black, - = Orange, HES #1 signal = Red, HES #2 signal = Brown.  

According to the K75 schematic I have, the BMW colours should be + = Red, - = Black, HES #1 signal = Orange, HES #2 signal = Brown.

Although the wire colours don't make sense, there is also a discrepancy in between the BMW schematic and the actual wiring.  I presume that the pin allocation on the connector is correct despite the discrepancy.

i seem to recall that there were quite a few , discrepancies in the wiring colour rob , but worked all the same  ,, a bit like tank wiring which i have found confusing but when metered out , proved ok

Yep - looks right to me. After my experiences trying to make sense of the HES wiring, I came to the conclusion that BMW do something crazy in the ICU along the lines of a series/parallel connection.

I don't get why BMW (or Bosch) would use black for ground and brown for a signal when everything else on a K uses brown for ground.