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Home >> Mazda >> 2017 >> CX-9 Touring, AWD >> Repair and Diagnosis (Single Page) >> Brakes >> Anti-Lock Brakes >> On-Board Diagnostic - Dynamic Stability Control (DSC) >> DTC C0023-62; C0040-64; Brake Switch MALFUCNTION >> Diagnostic Procedure

Diagnostic Procedure

Without Smart Brake Support (SBS)/With Smart City Brake Support (SCBS)

DIAGNOSTIC PROCEDURE

Step Inspection Action
1 INSPECT BRAKE LIGHT RELAY VOLTAGE
  • Remove the brake light relay. (See RELAY LOCATION .)
  • Measure the voltage between brake light relay terminal B (wiring harness-side) and body ground.
  • Is the voltage within followings?
  • Brake pedal depressed: B+
  • Brake pedal released: 1.0 V or less
 Yes Go to step 4.
No
  • If it is B+ under any condition, then go to the next step.
  • If it is 1.0 V or less under any condition, then go to Step 3.
2 INSPECT BRAKE SWITCH Yes Refer to the wiring diagram and verify whether or not there is a common connector between brake switch terminal D and brake light relay terminal B.
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 power circuit.
  • Repair or replace the malfunctioning part.

    If there is no common connector:

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

Go to step 7.
No Replace the brake switch, then go to step 7.
(See BRAKE PEDAL REMOVAL/INSTALLATION .)
3 INSPECT BRAKE SWITCH Yes Refer to the wiring diagram and verify whether or not there is a common connector between brake switch terminal D and brake light relay terminal B.
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 or short to ground circuit.
  • Repair or replace the malfunctioning part.

    If there is no common connector:

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

Go to step 7.
No Replace the brake switch, then go to step 7.
(See BRAKE PEDAL REMOVAL/INSTALLATION .)
4 INSPECT BRAKE LIGHT RELAY Yes Go to the next step.
No Replace the brake light relay, then go to step 7.
5 INSPECT WIRING HARNESS BETWEEN BRAKE LIGHT RELAY AND DSC HU/CM FOR OPEN OR SHORT CIRCUIT
  • Disconnect the DSC HU/CM connector.
  • Measure the voltage between DSC HU/CM terminal O (wiring harness-side) and body ground.
  • Is the voltage within followings?
    • Brake pedal depressed: B+
      • Brake pedal released: 1.0 V or less
 Yes Go to the next step.
No
  • If it is B+ under any condition, refer to the wiring diagram and verify whether or not there is a common connector between brake light relay terminal D and DSC HU/CM terminal O.

    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 power circuit.
  • Repair or replace the malfunctioning part.

    If there is no common connector:

  • Repair or replace the wiring harness which has a short to power circuit.
  • If it is 1.0 V or less under any condition, refer to the wiring diagram and verify whether or not there is a common connector between brake light relay terminal D and DSC HU/CM terminal O.

    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 or short to ground circuit.
  • Repair or replace the malfunctioning part.

    If there is no common connector:

  • Repair or replace the wiring harness which has an open or short to ground circuit.
  • Go to step 7.
6 VERIFY REAR BODY CONTROL MODULE (BCM) DTC Yes Go to the applicable DTC inspection.
(See DTC TABLE [REAR BODY CONTROL MODULE (RBCM)] .)
DTC troubleshooting completed, then go to the next step.
No Go to the next step.
7 VERIFY DTC TROUBLESHOOTING COMPLETED Yes If the malfunction recurs, replace the DSC HU/CM, then go to the next step.
(See DSC HU/CM REMOVAL/INSTALLATION .)
No Go to the next step.
8 VERIFY NO DTC IS PRESENT
  • Are any DTCs present?
 Yes Go to the applicable DTC inspection.
(See DTC TABLE [DSC HU/CM] .)
No DTC troubleshooting completed.

With Smart Brake Support (SBS)

Step Inspection Action
1 INSPECT BRAKE LIGHT UNIT VOLTAGE
  • Disconnect the brake light unit connector.
  • Measure the voltage between brake light unit terminal I (wiring harness-side) and body ground.
  • Is the voltage within followings?
  • Brake pedal depressed: B+
  • Brake pedal released: 1.0 V or less
 Yes Go to step 4.
No
  • If it is B+ under any condition, then go to the next step.
  • If it is 1.0 V or less under any condition, then go to Step 3.
2 INSPECT BRAKE SWITCH Yes Refer to the wiring diagram and verify whether or not there is a common connector between brake switch terminal D and brake light unit terminal I.
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 power circuit.
  • Repair or replace the malfunctioning part.

    If there is no common connector:

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

Go to step 6.
No Replace the brake switch, then go to step 6.
(See BRAKE PEDAL REMOVAL/INSTALLATION .)
3 INSPECT BRAKE SWITCH Yes Refer to the wiring diagram and verify whether or not there is a common connector between brake switch terminal D and brake light unit terminal I.
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 or short to ground circuit.
  • Repair or replace the malfunctioning part.

    If there is no common connector:

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

Go to step 6.
No Replace the brake switch, then go to step 6.
(See BRAKE PEDAL REMOVAL/INSTALLATION .)
4 INSPECT WIRING HARNESS BETWEEN BRAKE LIGHT UNIT AND DSC HU/CM FOR OPEN OR SHORT CIRCUIT
  • Disconnect the DSC HU/CM connector.
  • Measure the voltage between DSC HU/CM terminal O (wiring harness-side) and body ground.
  • Is the voltage within followings?
    • Brake pedal depressed: B+
      • Brake pedal released: 1.0 V or less
 Yes Go to the next step.
No
  • If it is B+ under any condition, refer to the wiring diagram and verify whether or not there is a common connector between brake light unit terminal H and DSC HU/CM terminal O.

    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 power circuit.
    • Repair or replace the malfunctioning part.

      If there is no common connector:

    • Repair or replace the wiring harness which has a short to power circuit.
  • If it is 1.0 V or less under any condition, refer to the wiring diagram and verify whether or not there is a common connector between brake light unit terminal H and DSC HU/CM terminal O.

    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 or short to ground circuit.
  • Repair or replace the malfunctioning part.

    If there is no common connector:

  • Repair or replace the wiring harness which has an open or short to ground circuit.
  • Go to step 6.
5 INSPECT BRAKE LIGHT UNIT Yes Go to the next step.
No Replace the brake light unit, then go to the next step.
(See BRAKE LIGHT UNIT REMOVAL/INSTALLATION .)
6 VERIFY DTC TROUBLESHOOTING COMPLETED Yes If the malfunction recurs, replace the DSC HU/CM, then go to the next step.
(See DSC HU/CM REMOVAL/INSTALLATION .)
No Go to the next step.
7 VERIFY NO DTC IS PRESENT
  • Are any DTCs present?
 Yes Go to the applicable DTC inspection.
(See DTC TABLE [DSC HU/CM] .)
No DTC troubleshooting completed.
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