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Free to use workshop manual for your 2015+ Mk4 'ND' Mazda MX-5
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BODY CONTROL MODULE (BCM) INSPECTION

1. Disconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)
2. Remove the scuff plate (driver's side). (See SCUFF PLATE REMOVAL/INSTALLATION.)
3. Remove the front side trim (driver's side). (See FRONT SIDE TRIM REMOVAL/INSTALLATION.)
4. Remove the BCM. (See BODY CONTROL MODULE (BCM) REMOVAL/INSTALLATION.)
5. Connect the BCM connector.
6. Connect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)
7. Verify that the voltages of each of the terminals are as indicated in the terminal voltage table (reference). (See Terminal Voltage Table (Reference).)

  • If the voltage is not as specified in the terminal voltage table (reference), inspect the parts under Inspection item(s) and related wiring harnesses.

    • If the system does not work normally even though the inspection items are normal, identify the malfunctioning location according to the directions in [DIAGNOSTIC SYSTEM] and [SYMPTOM TROUBLESHOOTING] then perform repairs.

Terminal Voltage Table (Reference)

Terminal

Signal

Connected to

Measurement condition

Voltage (V)

Inspection item(s)

1A

Power supply

HAZARD 15 A fuse

Under any condition

B+

HAZARD 15 A fuse

1B

Power supply

  • ROOM 25 A fuse

  • INTERIOR 15 A fuse

Under any condition

B+

  • ROOM 25 A fuse

  • INTERIOR 15 A fuse

1C

—

—

—

—

—

1D

—

—

—

—

—

1E

Rear turn light (RH) control

Rear turn light (RH)

Ignition is switched ON (engine off or on)

Turn switch is in right turn position

1.0 or less ↔ B+

Rear turn light (RH)

Turn switch is in position other than above

1.0 or less

1F

—

—

—

—

—

1G

Rear turn light (LH) control

Rear turn light (LH)

Ignition is switched ON (engine off or on)

Turn switch is in left turn position

1.0 or less ↔ B+

Rear turn light (LH)

Turn switch is in position other than above

1.0 or less

1H

Interior light power supply

Map light

Under any condition

B+

Map light

1I

—

—

—

—

—

1J

—

—

—

—

—

1K

Ground

Body ground

Under any condition

1.0 or less

Body ground

1L

Ground

Body ground

Under any condition

1.0 or less

Body ground

2A

Lock input (door lock-link switch (driver's side))

Door latch and lock actuator (driver's side)

Driver's door is locked

1.0 or less

Door latch and lock actuator (driver's side)

Driver's door is unlocked

Approx. 10

2B

Unlock input (door lock-link switch (driver's side))

Door latch and lock actuator (driver's side)

Driver's door is locked

Approx. 9.5

Door latch and lock actuator (driver's side)

Driver's door is unlocked

1.0 or less

2C

CAN_L

CAN system related module

Terminal used for communication therefore determination based on terminal voltage is not possible.

2D

CAN_H

CAN system related module

Terminal used for communication therefore determination based on terminal voltage is not possible.

2E

Top lock switch signal

Top lock switch

Convertible top is open

1.0 or less

Top lock switch

Convertible top is closed

Approx. 9.5

2F

—

—

—

—

—

2G

Door latch switch (passenger's side) signal

Door latch and lock actuator (passenger's side)

Door (passenger's side) is open

1.0 or less

Door latch and lock actuator (passenger's side)

Door (passenger's side) is closed

Approx. 9.0

2H

Door latch switch (driver's side) signal

Door latch and lock actuator (driver's side)

Door (driver's side) is open

1.0 or less

Door latch and lock actuator (driver's side)

Door (driver's side) is closed

Approx. 9.5

2I

—

—

—

—

—

2J

Serial communication

Start stop unit

Terminal used for communication therefore determination based on terminal voltage is not possible.

2K*1

Door lock switch signal

Door lock switch (RH)

Door lock switch is turned to unlock side (driver’s side or passenger’s side)

1.0 or less

Door lock switch (RH)

Door lock switch is turned to lock side (driver’s side or passenger’s side)

Approx. 1.25

Other

Approx 5.0

2L

Door key cylinder switch signal

Door latch and lock actuator (driver’s side)

Door key cylinder is turned to unlock side

1.0 or less

Door latch and lock actuator (driver’s side)

Door key cylinder is turned to lock side

Approx. 1.25

Other

Approx 5.0

2M*2

Lock input (door lock-link switch (passenger's side))

Door latch and lock actuator (passenger's side)

Passenger’s door is unlocked

1.0 or less

Door latch and lock actuator (passenger's side)

Passenger’s door is locked

B+

2N

—

—

—

—

—

2O

—

—

—

—

—

2P

—

—

—

—

—

2Q

Fuel sensor signal

Fuel gauge sender unit

Inspect fuel gauge sender unit and related wiring harness because determination based on terminal voltage is not possible.

(See FUEL GAUGE SENDER UNIT INSPECTION.)

2R

Fuel sensor ground

Fuel gauge sender unit

Under any condition

1.0 or less

Fuel gauge sender unit

2S

Trunk lid unlatch switch signal (exterior)

Trunk lid opener switch (exterior)

Trunk is opened

1.0 or less

Trunk lid opener switch (exterior)

Trunk is closed

Approx. 4.5

2T

—

—

—

—

—

2U

—

—

—

—

—

2V

—

—

—

—

—

2W

—

—

—

—

—

2X

—

—

—

—

—

2Y

LIN communication

Electrical supply unit (ESU)

Terminal used for communication therefore determination based on terminal voltage is not possible.

2Z

—

—

—

—

—

2AA

—

—

—

—

—

2AB

—

—

—

—

—

2AC

Trunk lid latch switch signal

Trunk lid latch and release actuator

Trunk is opened

1.0 or less

Trunk lid latch and release actuator

Trunk is closed

Approx. 9.5

2AD

—

—

—

—

—

2AE

—

—

—

—

—

2AF

—

—

—

—

—

3A

Front turn light (RH) control

Front turn light (RH)

Ignition is switched ON (engine off or on)

Turn switch is in right turn position

1.0 or less ↔ B+

Front turn light (RH)

Turn switch is in position other than above

1.0 or less

3B

Front turn light (LH) control

Front turn light (LH)

Ignition is switched ON (engine off or on)

Turn switch is in left turn position

1.0 or less ↔ B+

Front turn light (LH)

Turn switch is in position other than above

1.0 or less

3C

CAN_H

CAN system related module

Terminal used for communication therefore determination based on terminal voltage is not possible.

3D

CAN_L

CAN system related module

Terminal used for communication therefore determination based on terminal voltage is not possible.

3E

Blower motor relay control

  • Blower relay

  • HEATER 40 A fuse

Ignition is switched ON (engine off or on)

Blower motor is operated using fan switch

1.0 or less

  • Blower relay

  • HEATER 40 A fuse

Blower motor is turned off by pressing climate control unit OFF button

B+

3F

Windshield wiper INT relay control

Wiper INT relay

Ignition is switched ON (engine off or on)

Windshield wiper switch is in position other than OFF

1.0 or less

Wiper INT relay

Windshield wiper switch is in OFF position

B+

3G

Windshield wiper motor (HI) control

Wiper HI relay

Ignition is switched ON (engine off or on)

Windshield wiper switch is in HIGH position

1.0 or less

Wiper HI relay

Windshield wiper switch is in OFF position

B+

3H

Horn relay control

Horn relay

Ignition is switched ON (engine off or on)

Horn switch is on

1.0 or less

Horn relay

Horn switch is off

B+

3I

—

—

—

—

—

3J

—

—

—

—

—

3K

Rear window defogger relay control

Rear window defogger relay

Ignition is switched ON (engine off or on)

Rear window defogger switch is on

1.0 or less

Rear window defogger relay

Rear window defogger switch is off

B+

3L

—

—

—

—

—

3M

Autostop switch signal

Wiper motor

Ignition is switched ON (engine off or on)

Wiper switch is on and wiper is operating

1.0 or less

Wiper motor

Wiper switch is off

B+

3N

Power supply

  • ENG+B 7.5 A fuse

  • ROOM 25 A fuse

Under any condition

B+

  • ENG+B 7.5 A fuse

  • ROOM 25 A fuse

3O

Ignition power supply

METER1 10 A fuse

Ignition is switched ON (engine off or on)

B+

METER1 10 A fuse

The ignition is switched off (LOCK)

1.0 or less

3P

—

—

—

—

—

3Q*3

Washer fluid level sensor signal

Washer fluid level sensor

Ignition is switched ON (engine off or on)

Washer fluid level sensor is less than MIN (washer fluid level sensor on)

1.0 or less

Washer fluid level sensor

Washer fluid level sensor is MIN or more (Washer fluid level sensor off)

B+

3R

Brake fluid level sensor signal

Brake fluid level sensor

Ignition is switched ON (engine off or on)

Brake fluid level sensor is less than MIN (brake fluid level sensor on)

1.0 or less

Brake fluid level sensor

Brake fluid level sensor is MIN or more (brake fluid level sensor off)

B+

3S

—

—

—

—

—

3T

Horn switch control

Horn switch

Ignition is switched ON (engine off or on)

Horn switch is on (long press)

1.0 or less

Horn switch

Horn switch is off

B+

3U

Trunk unlatch switch signal (interior)

Trunk lid opener switch (interior)

Trunk lid opener switch (interior) is on (trunk lid opener switch (interior) is pressed)

1.0 or less

Trunk lid opener switch (interior)

Trunk lid opener switch (interior) is off (trunk lid opener switch (interior) is not pressed)

B+

3V

—

—

—

—

—

3W*5

Hood latch switch signal

Hood latch switch

Hood is open

Approx. 9.0

Hood latch switch

Hood is closed

1.0 or less

3X

LIN communication

Auto-light sensor/rain sensor*4

Terminal used for communication therefore determination based on terminal voltage is not possible.
*1
With door lock switch
*2
With front fog light
*3
With washer fluid level sensor
*4
With auto light system/auto wiper system
*5
With hood latch switch
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Free to use workshop manual for your 2015+ Mk4 'ND' Mazda MX-5

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