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Home >> Nissan-Datsun >> 2004 >> Sentra SE-R >> Repair and Diagnosis >> External Pages >> Different car >> Section 813 (BCM (Body Control Module)) >> BCM (Body Control Module) >> System Description >> Combination Switch Reading Function
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Combination Switch Reading Function

WARNING: This page is about a different car, the 2003 Nissan Altima. However, it is still accessible from the selected car via links, so may be relevant.
  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) activate 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 BCM judges switches are ON.
    Fig 1: Combination Switch/BCM Operation Description
    G02162978Courtesy of NISSAN MOTOR CO., U.S.A.
  3. Example (When fog lamp switch is turned ON)
    • When fog lamp switch is turned ON, contact in combination switch turns ON. At this time if OUTPUT 4 transistor is activated, BCM detects current flow in INPUT 5.
    • When OUTPUT 4 transistor is ON, BCM detects current flow in INPUT5, and judges fog lamp switches is ON. Then BCM sends fog lamp ON signal to IPDM E/R using CAN communication.
    • When OUTPUT 4 transistor is activated again, BCM detects current flow in INPUT 5, and confirms fog lamp switch is continuously ON.
    Fig 2: Combination Switch/BCM Operation - Fog Lamp Switch Turned ON
    G02162979Courtesy of NISSAN MOTOR CO., U.S.A.
    NOTE: Each OUTPUT terminal transistor is activated at 10 ms interval. 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.
  4. BCM - Operation table of combination switches
    • BCM reads operation status of combination switches by the combination shown in Fig 3.
    Fig 3: BCM/Combination Switches - Operation Table
    G02162980Courtesy of NISSAN MOTOR CO., U.S.A.
    NOTE: Headlamp has a dual system switch for safe operation.
  5. Operation mode
    • Combination switch reading function has operation modes shown in Fig 4.
  1. Normal mode
    • When BCM is not is sleep mode, each OUTPUT (1 - 5) terminal turns ON-OFF at 10 ms intervals.
  2. 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) turn ON-OFF at 60 ms intervals, and receives lighting switch input only.
    Fig 4: BCM Normal/Sleep Modes
    G02162981Courtesy of NISSAN MOTOR CO., U.S.A.
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