Wiper Switch: Description and Operation

BCM Wiper Switch Reading Function
BCM reads combination switch (wiper switch) status, and controls front wipers based on the results. BCM is a combination of 5 output terminals (OUTPUT 1 - 5) and 5 input terminals (INPUT 1 - 5). It reads 20 types of switch data and 5 types of diagnosis data.

OPERATION DESCRIPTION
BCM continuously outputs power voltage from input terminals (INPUT 1 - 5). At this time, output terminals (OUTPUT 1 - 5) operate transistors in sequence and carry current. If any switch (or switches) become ON at this time, the input terminal corresponding to that switch detects current flowing, and BCM determines that the switch is ON.




TABLE OF BCM - COMBINATION SWITCH OPERATIONS
BCM reads operation status of combination switch using combinations shown in table.

SAMPLE OPERATION: (WIPER SWITCH TURNED TO LO POSITION)
- When wiper switch is turned to LO position, front wiper LO contact inside combination switch becomes ON. At this time, OUTPUT 3 transistor operates and BCM detects flow of current at INPUT 1.
- When OUTPUT 3 transistor is ON and BCM detects current flowing at INPUT 1, BCM determines that wiper switch is at LO. BCM uses CAN communication and sends front wiper signals to IPDM E/R.
- When OUTPUT 3 transistor operates again and BCM again detects current flowing at INPUT 1, it confirms that front wiper LO operation is continuing.






NOTE: Each OUTPUT terminal transistor operates at 10 ms intervals. Therefore, a delay occurs between the switch becoming ON and operation of the electric load. However, this delay is so small it is undetectable by human senses.

OPERATING MODES
The following operation modes exist for combination switch reading function.

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, output from OUTPUT 1 and 2 transistors stops, with BCM entering a power-saving mode. OUTPUT (3 - 5) turn ON-OFF every 60 ms, and only input from light switch system is accepted.

INTERMITTENT OPERATION
Wiper intermittent operation delay interval is determined from a combination of 3 switches (intermittent operation dial position 1 intermittent operation dial position 2, and intermittent operation dial position 3) and vehicle speed signal.

During each intermittent operation delay interval, BCM sends front wiper request signal to IPDM E/R.

Wiper Dial Position Setting:

Example: For wiper dial position 1...

Using combination switch reading function, BCM detects ON/OFF status of intermittent operation dial positions 1, 2, and 3.

When combination switch status is as listed below, BCM determines that it is wiper dial position 1.
- Intermittent operation dial position 1: ON (input 3 and output 2 are conducting.)
- Intermittent operation dial position 2: ON (input 5 and output 2 are conducting.)
- Intermittent operation dial position 3: ON (input 4 and output 1 are conducting.)

BCM determines front wiper intermittent operation delay interval from wiper dial position 1 and vehicle speed, and sends wiper request signal (INT) to IPDM E/R.