Combination Switch Reading Function
WARNING: This page is about a different car, the 2004 Nissan Murano. However, it is still accessible from the selected car via links, so may be relevant.
- Description
- BCM reads combination switch (light, wiper) status, and controls related systems such as head lamps and wipers, according to the results.
- BCM reads information of a maximum of 20 switches by combining five output terminals (OUTPUT 1-5) and five input terminals (INPUT 1-5).
- Operation description
- BCM activates transistors of output terminals (OUTPUT 1-5) periodically and, allows current to flow in turn.
- If any (1 or more) switches are turned ON, circuit of output terminals (OUTPUT 1-5) and input terminals (INPUT 1-5) becomes active.
- At this time, transistors of output terminals (OUTPUT 1-5) are activated to allow current to flow. When voltage of input terminals (INPUT 1-5) corresponding to that switch changes, interface in BCM detects voltage change, and BCM determines that switch is ON.
- BCM - Operation table of combination switches
- BCM reads operation status of combination switch using combinations shown in table below.
NOTE: Headlamp has a dual system switch.
- BCM reads operation status of combination switch using combinations shown in table below.
- Sample operation: (When lighting switch 1st position turned ON)
- When lighting switch 1st position is turned ON, contact in combination switch turns ON. At this time if OUTPUT 4 transistor is activated, BCM detects that voltage changes in INPUT 5.
- When OUTPUT 4 transistor is ON, BCM detects that voltage changes in INPUT 5, and judges that lighting switch 1st position is ON. Then BCM sends tail lamp ON signal to IPDM E/R using CAN communication.
- When OUTPUT 4 transistor is activated again, BCM detects that voltage changes in INPUT 5, and recognizes that lighting switch 1st position is continuously ON.
NOTE: Each OUTPUT terminal transistor is activated at 10 ms intervals. Therefore after switch is turned ON, I electrical loads are activated with time delay. But this time delay is so short that it cannot be detected by human senses.
- Operation mode
- Combination switch reading function has operation modes shown below.
- Normal status
- When BCM is not in sleep status, OUTPUT terminals (1-5) each turn ON-OFF every 10 ms.
- Sleep status
- When BCM is in sleep status, transistors of OUTPUT 1 and 5 stop the output, and BCM enters low current consumption mode. OUTPUT (2, 3, and 4) turn ON-OFF every 10 ms, and only input from light switch system is accepted.