BMW GM V Door Lock Relay Schematic and Explaination
Ok, here is the data for which relay is energized when. From my testing there are 4 modes: Unlock All Doors, Unlock Driver Door, Lock All Doors via Remote, Lock All Doors via Center Console. Each of these activated a different combination of relays. I'm calling the relay closest to the connector RLY1 and the other one RLY2. Now these are Double relays with two completely independant relays inside. I'm going to call the relay closer to the connector A and the other one B. So there are four relays total: RLY1-A, RLY1-B, RLY2-A and RLY2-B.
1) When unlocking all doors only relay RLY1-B energizes. Why only one relay energizes to unlock all doors puzzled me until I diagrammed the whole system. Schematic
2) When unlocking just the drivers door relays RLY1-A and RLY1-B energized. Hmmm, RLY1-A seems to be used to disable the passenger doors from unlocking.
3) When locking all doors via the center console button relays RLY1-A and RLY2-B energize.
4) When locking all doors via the remote relays RLY1-A, RLY2-A and RLY2-B energize. It seems like relay RLY2-A locks the double lock features. RLY2-B seems to be for locking. Not sure why RLY1-A needs to be energized during locking and unlocking of just the drivers door. It may sound strange, but, after analyzing it with the schematic I pieced together using the Bentley wiring diagram and the traces on the circuit board I was able to come up with a set of drawings that very clearly shows what is happening. This also gave a little insight into why these relays are failing.
First let me start off by saying that in the rest state all the relays connect 14-15 (or 24-25) which sends ground to all the door lock motors. Blue arrows indicate a motor unlocking. A red arrow indicates a motor locking. A black arrow indicates current flow (from the electrical engineering viewpoint, if you are looking at this from the physics viewpoint just reverse the direction of the arrows to indicate electron flow).
I figured out what the BL, WS and SW letters mean. BL is Blue, WS is White and SW is Black.
1) The schematic below is what happens when all doors are being unlocked with the remote. In this case only RLY1-B is energized sending +12V to all the BL wires of the motors. This unlocks both the deadbold motors and the lock motors. In this case poor little RLY1-B must supply current for 8 motors simultaneously.
2) The schematic below is what happens when only the driver door is being unlocked. In this case two relays are energized, RLY1-B, as in the unlock all case above and RLY1-A. Again RLY1-B sends +12V to all the BL wires of the motors which would normally unlock all doors, but, RLY1-A is also energized disconnecting the return path for the passenger door lock motors. This means that only the deadbolt motors and the driver door motor get power.
3) Next is the lock all doors using the central locking button. This does not lock the deadbolts, that is only controlled by the key fob remote or via the driver door key. In this case RLY1-A and RLY2-B are energized. This supplies +12V to the WS wires of all the door lock motors. RLY1-A for the passenger doors and RLY2-B for just the driver door. This does not supply power to the deadbolt motors.
4) Next is the lock all via the alarm case. When using the key fob or the driver door key hole to lock the car everything locks including the deadbolts. In this case three relays are energized, RLY1-A and RLY2-B as in the case above and RLY2-A. RLY1-A locks the passenger doors, RLY2-B locks just the driver door and RLY2-A locks all the deadbolts. Again poor little RLY1-B, even though it's not energized must supply the return path for all the motors simultaneously.
Conclusion:
I believe that it is RLY1-B that is most likely to go bad first. It gets hit the hardest during locking and unlocking. Now most people, including myself seem to have the most problem with unlocking. This involves contacts 13-15 of RLY1-B. I believe that since these are low current coils that when the relay is energized the 13-15 contact is not making very good contact. The next time I repair a GM V module I'll tear open the relay and take a look at the pin 13 contact of RLY1. I suspect it will look really black and pitted. I'll post pictures if they look interesting.
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