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Free to use workshop manual for your 2015+ Mk4 'ND' Mazda MX-5
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LF CONTROL UNIT INSPECTION

1. Remove the scuff plate (RH). (See SCUFF PLATE REMOVAL/INSTALLATION.)
2. Remove the front side trim (RH). (See FRONT SIDE TRIM REMOVAL/INSTALLATION.)
3. Verify that the voltages of each of the terminals are as indicated in the 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 or related wiring harnesses do not have any malfunction, replace the LF control unit. (See LF CONTROL UNIT REMOVAL/INSTALLATION.)

Terminal Voltage Table (Reference)

Terminal

Signal name

Connected to

Measurement conditions

Voltage (V)

Inspection item (s)

A

Request switch signal (RF)

Request switch (RF)

When request switch (RF) is pressed

1.0 or less

  • Request switch (RF)

When request switch (RF) is not pressed

5.0

B

Power supply

INTERIOR 15 A fuse

Under any condition

B+

  • ROOM 25A fuse

  • INTERIOR 15 A fuse

  • Battery

C

Request switch signal (LF)

Request switch (LF)

When request switch (LF) is pressed

1.0 or less

  • Request switch (LF)

When request switch (LF) is not pressed

5.0

G

Start stop unit signal

Start stop unit

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

H

Keyless beeper power supply

Keyless beeper

When lock button on remote transmitter is pressed or front door request switch is pressed to lock

Wave pattern (See Pattern 1.)

  • Keyless beeper

Except above

1.0 or less

I

Start stop unit signal

Start stop unit

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

J

GROUND

Keyless beeper

Under any condition

1.0 or less

  • Keyless beeper

K

Keyless antenna (interior, front)

Keyless antenna (interior, front)

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

L

GROUND

Body ground

Under any condition

1.0 or less

Body ground

M

Keyless antenna (interior, front)

Keyless antenna (interior, front)

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

O

Keyless antenna (exterior, LF)

Keyless antenna (exterior, LF)

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

P

Keyless antenna (interior, rear)

Keyless antenna (interior, rear)

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

Q

Keyless antenna (exterior, LF)

Keyless antenna (exterior, LF)

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

R

Keyless antenna (interior, rear)

Keyless antenna (interior, rear)

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

S

Keyless antenna (exterior, RF)

Keyless antenna (exterior, RF)

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

T

Keyless antenna (interior, center)

Keyless antenna (interior, center)

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

U

Keyless antenna (exterior, RF)

Keyless antenna (exterior, RF)

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

V

Keyless antenna (interior, center)

Keyless antenna (interior, center)

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

W

Keyless antenna (exterior, rear)

Keyless antenna (exterior, rear)

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

X

Keyless antenna (exterior, rear)

Keyless antenna (exterior, rear)

Because this terminal is for communication, integrity determination using terminal voltage inspection is not possible.

Inspection Using an Oscilloscope (Reference)

Pattern 1

  • LF control unit: H (+) ??? body ground (-)

  • Oscilloscope setting: 2 V/DIV (Y), 100 ms/DIV (X), DC range

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Free to use workshop manual for your 2015+ Mk4 'ND' Mazda MX-5

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