E36X Main Relay and O2 Heater Relay Control

[bmwman91]

From looking at the manual's pinout, and in PCLink, I do not see the main and O2 heater relays listed under nay of the aux outputs. Are the relays' operating coils controlled via discrete logic & the ignition switch input on the E36X, or am I missing a setting somewhere in PCLink?

My application is not a BMW M50, but another engine which also happens to use the 88 position main connector, and it'll help me decide how I want to re-pin a couple of wires once I know how those two relays are activated. The wiring is substantially similar to that of the M50, with the O2 heater relay's power coming from the output of the fuel pump relay, so really I am interested to know the conditions under which the main & O2 heater relays are active if they are not controlled via programmable outputs.

Thanks.

[Adamw]

The main relay is all controlled by dedicated hardware on the bottom board.  

When the relay control circuit receives 12V on pin 56 (ignition switch), it grounds pin 27 which is the main relay coil.  The main relay contacts then engage and supply 12V to pin 54 which powers up the ecu.  

[bmwman91]

16 hours ago, Adamw said:

The main relay is all controlled by dedicated hardware on the bottom board.  

When the relay control circuit receives 12V on pin 56 (ignition switch), it grounds pin 27 which is the main relay coil.  The main relay contacts then engage and supply 12V to pin 54 which powers up the ecu.  

Thanks Adam.

How about the O2 heater relay control?

[Adamw]

Pin 1 & pin 38 are connected together internally.  So O2 heater runs whenever the fuel pump runs.  These pins are controlled by Aux 8.