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DTC C0040:23 [START STOP UNIT]

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2016 – MX-5 – Body and Accessories

DTC C0040:23 [START STOP UNIT]

Description

Brake switch (No.1 signal) circuit malfunction

Detection condition

  • The start stop unit detected the following condition 5 times continuously with the ignition switched ON (engine off or on).

    • The brake switch (No.1 signal) is OFF for a continuous 3 s or more even though the brake switch (No.2 signal) changes.

Fail-safe

  • Determined by brake switch (No.2 signal) with the brake pedal depressed.

Possible cause

  • Brake switch connector or terminal malfunction

  • Brake switch (No.1 signal) malfunction

  • Brake switch (No.1 signal) power supply circuit malfunction

    • Short to ground in wiring harness between MAIN 200 A fuse and brake switch terminal A

    • STOP 10 A fuse malfunction

    • MAIN 200 A fuse malfunction

    • Open circuit in wiring harness between battery positive terminal and brake switch terminal A

  • Start stop unit connector or terminal malfunction

  • Short to ground in wiring harness between brake switch terminal D and start stop unit terminal 1C

  • Open circuit in wiring harness between brake switch terminal D and start stop unit terminal 1C

  • Start stop unit malfunction

Diagnostic Procedure

Step

Inspection

Action

1

INSPECT BRAKE SWITCH CONNECTOR CONDITION

  • Switch the ignition off.

  • Disconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • Disconnect the brake switch connector.

  • Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection.

  • Is the connector normal?

Yes

Go to the next step.

No

Repair or replace the connector, then go to Step 7.

2

INSPECT BRAKE SWITCH (No.1 SIGNAL)

Yes

Go to the next step.

No

Replace the brake switch, then go to Step 7.

(See BRAKE PEDAL REMOVAL/INSTALLATION.)

3

INSPECT BRAKE SWITCH (No.1 SIGNAL) POWER SUPPLY CIRCUIT FOR OPEN CIRCUIT OR SHORT TO GROUND

  • Verify that the brake switch connector is disconnected.

  • Connect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • Measure the voltage at the brake switch terminal A (wiring harness-side).

  • Is the voltage B+?

Yes

Go to the next step.

No

Inspect the STOP 10 A fuse and MAIN 200 A fuse.

  • Any fuse is blown:

    • Refer to the wiring diagram and verify whether or not there is a common connector between MAIN 200 A fuse and brake switch terminal A.

      • If there is a common connector:

      • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground.

      • Repair or replace the malfunctioning part.

        If there is no common connector:

      • Repair or replace the wiring harness which has a short to ground.

      • Replace the fuse.

  • Any fuse is damaged:

    • Replace the fuse.

  • All fuses are normal:

    • Refer to the wiring diagram and verify whether or not there is a common connector between battery positive terminal and brake switch terminal A.

      • If there is a common connector:

      • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.

      • Repair or replace the malfunctioning part.

        If there is no common connector:

      • Repair or replace the wiring harness which has an open circuit.

Go to Step 7.

4

INSPECT START STOP UNIT CONNECTOR CONDITION

  • Disconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • Disconnect the start stop unit connector.

  • Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection.

  • Is the connector normal?

Yes

Go to the next step.

No

Repair or replace the connector, then go to Step 7.

5

INSPECT BRAKE SWITCH (No.1 SIGNAL) CIRCUIT FOR SHORT TO GROUND

  • Verify that the brake switch and start stop unit connectors are disconnected.

  • Inspect for continuity between brake switch terminal D (wiring harness-side) and body ground.

  • Is there continuity?

Yes

Refer to the wiring diagram and verify whether or not there is a common connector between brake switch terminal D and start stop unit terminal 1C.

    If there is a common connector:

  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground.

  • Repair or replace the malfunctioning part.

    If there is no common connector:

  • Repair or replace the wiring harness which has a short to ground.

Go to Step 7.

No

Go to the next step.

6

INSPECT BRAKE SWITCH (No.1 SIGNAL) CIRCUIT FOR OPEN CIRCUIT

  • Verify that the brake switch and start stop unit connectors are disconnected.

  • Inspect for continuity between brake switch terminal D (wiring harness-side) and start stop unit terminal 1C (wiring harness-side).

  • Is there continuity?

Yes

Go to the next step.

No

Refer to the wiring diagram and verify whether or not there is a common connector between brake switch terminal D and start stop unit terminal 1C.

    If there is a common connector:

  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.

  • Repair or replace the malfunctioning part.

    If there is no common connector:

  • Repair or replace the wiring harness which has an open circuit.

Go to the next step.

7

VERIFY THAT REPAIRS HAVE BEEN COMPLETED

Yes

Repeat the inspection from Step 1.

Go to the next step.

No

Go to the next step.

8

VERIFY IF OTHER DTCs DISPLAYED

  • Are any other DTCs displayed?

Yes

Repair or replace the malfunctioning part according to the applicable DTC troubleshooting.

(See DTC TABLE [START STOP UNIT].)

No

DTC troubleshooting completed.

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