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Home >> Mazda >> 2019 >> 6 Signature >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Communication Devices >> On-Board Diagnostics - Rear Body Control Module (RBCM) >> DTC B109E-87: Communication Error With Start Stop Unit >> Diagnostic Procedure

Diagnostic Procedure

DTC B109E:87 (REAR BODY CONTROL MODULE (RBCM)) 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
  • Switch the ignition off.
  • Disconnect the negative battery terminal. (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
  • 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 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.
  • Connect 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 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 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.
6 INSPECT FOR OPEN CIRCUIT IN WIRING HARNESS BETWEEN START STOP UNIT AND REAR BODY CONTROL MODULE (RBCM)
  • Switch the ignition off.
  • Disconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION .)
  • 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.
Go to the next step.
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.