MembersPage/BmwMFiftyTwo (2018-02-06 11:31:20)

BMW M52 engine.

Black mot88 connector lock is slightly different from the natural color M50 (either type can be used with a bit of filing).

The mot88 pinout is VERY different. So do NOT plug into the other type.

See [M50-vanos-vs-s50b32.xls] columns.


Prelling

We received a report of some relay prelling (when ignition off) that we cannot reproduce.

What should be hooked to the mot88 (which pin) to simulate the "ignition off" state ?

  • The flyback=mot88/87 (not pin54 in the xls beware, that is cam sensor +12V!) in the car also comes from the main relay but could possibly be moved to a constant 12V (pin26) instead to solve this?
  • good find: apparently the mot88/54 = mot88/49 (12V connection wire) inside the ECU is simply not needed, if the mot88/54 is supplied from the harness (weird, why is it connected back to the ECU at all ?)
  • Can a failed diode in the relay cause this?
  • possible, but more likely the mot88/54 cam12V seems to be unnecessary from the ECU if the harness feeds 12V there (via main relay) anyway

OEM wiring information here

http://www.gbnetwork.co.uk/bmw/ftp/etm_e36_1998final.zip

Page 108 shows the way it´s wired.


The bold, or last 2 are suspect to cause prelling, especially if switched 12V (ECU main supply) is connected to cam12V in the harness