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Home >> Mazda >> 2017 >> CX-5 Grand Select, FWD >> Repair and Diagnosis >> Accessories & Equipment >> Communication Devices >> On-Board Diagnostic - Rear Body Control Module (RBCM) >> DTC B109E-87; Communication Error With Start Stop Unit >> Diagnostic Procedure

Diagnostic Procedure

DIAGNOSTIC PROCEDURE

Step Inspection Action
1 VERIFY REAR BODY CONTROL MODULE (RBCM) DTCs AGAIN Yes Go to the next step.
No Go to Step 9.
2 INSPECT START STOP UNIT CONNECTOR CONDITION
  • Switch the ignition off.
  • Disconnect the negative battery cable. (See NEGATIVE BATTERY TERMINAL 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 8.
3 INSPECT REAR BODY CONTROL MODULE (RBCM) CONNECTOR CONDITION
  • Disconnect the rear body control module (RBCM) 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 8.
4 INSPECT FOR SHORT TO GROUND IN WIRING HARNESS BETWEEN START STOP UNIT AND REAR BODY CONTROL MODULE(RBCM)
  • Verify that the rear body control module (RBCM) and start stop unit connectors are disconnected.
  • Inspect for continuity between start stop unit terminal 1Q (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 rear body control module (RBCM) terminal 3B and start stop unit terminal 1Q.
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 8.

No Go to the next step.
5 INSPECT FOR SHORT TO POWER SUPPLY IN WIRING HARNESS BETWEEN START STOP UNIT AND REAR BODY CONTROL MODULE (RBCM)
  • Verify that the rear body control module (RBCM) and start stop unit connectors are disconnected.
  • Reconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION .)
  • Switch the ignition ON (engine off or on).
  • Measure the voltage at the start stop unit terminal 1Q (wiring harness-side).
  • Is the voltage 0 V?
Yes Refer to the wiring diagram and verify whether or not there is a common connector between rear body control module (RBCM) terminal 3B and start stop unit terminal 1Q.
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 supply.
  • Repair or replace the malfunctioning part.

    If there is no common connector:

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

    Go to Step 8.

No Go to the next step.
6 INSPECT FOR OPEN CIRCUIT IN WIRING HARNESS BETWEEN START STOP UNIT AND REAR BODY CONTROL MODULE (RBCM)
  • Verify that the rear body control module (RBCM) and start stop unit connectors are disconnected.
  • Inspect for continuity between rear body control module (RBCM) terminal 3B (wiring harness-side) and start stop unit terminal 1Q (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 rear body control module (RBCM) terminal 3B and start stop unit terminal 1Q.
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 8.

7 PERFORM DTC INSPECTION AND VERIFY START STOP UNIT MALFUNCTION Yes Replace the start stop unit, then go to the next step. (See START STOP UNIT REMOVAL/INSTALLATION .)
No Go to Step 9.
8 VERIFY THAT REPAIRS HAVE BEEN COMPLETED Yes Repeat the inspection from Step 1.
No Go to the next step.
9 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 [REAR BODY CONTROL MODULE (RBCM)] .)
No DTC troubleshooting completed.