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Home >> Nissan-Datsun >> 2003 >> 350Z Standard >> Repair and Diagnosis >> Accessories & Equipment >> Communication Devices >> Body Control Module >> BCM (Body Control Module) >> System Description >> Combination Switch Reading Function

Combination Switch Reading Function

  1. Description
    • BCM reads combination switch (light, wiper washer, turn signal) status, and controls various electrical components according to the results.
    • BCM reads information of 20 switches and 5 diagnostic results by combining five output terminals (OUTPUT 1-5) and five input terminals (INPUT 1-5).
  2. Operation description
    • BCM outputs battery voltage from input terminals (INPUT 1-5) all the time. At the same time output terminals (OUTPUT 1-5) active transistors in turn, and allow current to flow. At this time, if any (1 or more) of the switches are ON, the input terminals corresponding to these switches detect current flow, and the interface of BCM detects the condition. Then BCM judges switches are ON.
    Fig 1: BCM - Combination Switch Circuit
    G01343598Courtesy of NISSAN MOTOR CO., U.S.A.
  3. BCM-Operation table of combination switches.
    • BCM reads operation status of combination switches by the combination shown in the figure. See Fig 2.
    Fig 2: BCM-Operation Table Of Combination Switches
    G01343599Courtesy of NISSAN MOTOR CO., U.S.A.
    NOTE: Dual switches are set for head lamps.
  4. Example (When lighting switch 1st position is turned ON)
    • When lighting switch 1st position is turned ON, contact in combination switch turns ON. At this time if OUTPUT 5 transistor is activated, BCM detects current flow in INPUT 4.
    • When OUTPUT 5 transistor is ON, BCM detects current flow in INPUT 4, and judges lighting switch 1st position is ON. Then BCM sends tail lamp ON signal to IPDM E/R using CAN communication.
    • When OUTPUT 5 transistor is activated again, BCM detects current flow in INPUT 4, and confirms lighting switch 1st position is continuously ON.
    Fig 3: Identifying Current Flow - Lighting Switch 1st Position
    G01343600Courtesy of NISSAN MOTOR CO., U.S.A.
    NOTE: Each OUTPUT terminal transistor is activated at 10 ms intervals. Therefore, after a switch is turned ON, the electrical loads are activated with a time delay, but this time delay is so short that it cannot be noticed.
  5. Operation mode
    • Combination switch reading function has operation modes shown below.
    1. Normal mode
      • When BCM is not in sleep mode, each OUTPUT (1 - 5) terminal turns or ON-OFF at 10 ms intervals.
  6. Sleep mode
    • When BCM is in sleep mode, transistors of OUTPUT 1 and 2 stop the output, and BCM enters low-current-consumption mode. OUTPUTS (3 - 5) ON-OFF at 60 ms intervals, and receive lighting switch input only.
    Fig 4: Normal And Sleep Mode Blinking Pattern
    G01343601Courtesy of NISSAN MOTOR CO., U.S.A.
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