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Home >> Mazda >> 2017 >> CX-5 Grand Select, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 74 (On-Board Diagnostic - Rear Body Control Module (RBCM)) >> DTC B109E-87: Communication Error With Start Stop Unit >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2016 Mazda CX-5. However, it is still accessible from the selected car via links, so may be relevant.
Step Inspection Action
1 VERIFY REAR BODY CONTROL MODULE (RBCM) DTCs AGAIN 
Yes Go to the next step.
No Go to Step 8.
2 INSPECT START STOP UNIT CONNECTOR CONDITION 
Yes Go to the next step.
No Repair or replace the connector, then go to Step 7.
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 7.
4 INSPECT START STOP UNIT CIRCUIT FOR SHORT TO GROUND 
  • Verify that the rear body control module (RBCM) connector and start stop unit connector are disconnected.
  • Inspect for continuity between start stop unit terminal 1Q (vehicle wiring harness side) and body ground.
  • Is there continuity?
Yes Repair or replace the wiring harness which is shorted to ground, then go to Step 7.
No Go to the next step.
5 INSPECT START STOP UNIT CIRCUIT FOR OPEN CIRCUIT 
  • Verify that the rear body control module (RBCM) connector and start stop unit connector are disconnected.
  • Inspect the wiring harness for an open circuit between rear body control module (RBCM) terminal 3B (vehicle wiring harness side) and start stop unit terminal 1Q (vehicle wiring harness side).
  • Is there continuity?
Yes Go to the next step.
No Repair or replace the wiring harness which has an open circuit, then go to Step 7.
6 INSPECT START STOP UNIT 
Yes Go to the next step.
No Replace the start stop unit, then go to the next step.
(See START STOP UNIT REMOVAL/INSTALLATION .)
7 VERIFY THAT REPAIRS HAVE BEEN COMPLETED 
Yes Repeat the inspection from Step 1.
No Go to the next step.
8 VERIFY IF OTHER DTCs DISPLAYED 
  • Are any other DTCs displayed?
Yes Repair the malfunctioning part according to the applicable DTC troubleshooting.
(See DTC TABLE [REAR BODY CONTROL MODULE (RBCM)] .)
No DTC troubleshooting completed.