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DTC B109E-87: Communication Error With Start Stop Unit: Notes

WARNING: This page is about a different car, the 2018 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
DTC B109E:87 (REAR BODY CONTROL MODULE (RBCM)) DETECTION CONDITION AND POSSIBLE CAUSE

Description Communication Error With Start Stop Unit
Detection condition
  • Rear body control module (RBCM) detects a communication error with the start stop unit for 10 times continuously.
Fail-safe Not applicable
Possible cause
  • Start stop unit connector or terminal malfunction
  • Rear body control module (RBCM) connector or terminal malfunction
  • Short to ground in wiring harness between rear body control module (RBCM) terminal 3B and start stop unit terminal 1Q
  • Short to power supply in wiring harness between rear body control module (RBCM) terminal 3B and start stop unit terminal 1Q
  • Open circuit in wiring harness between rear body control module (RBCM) terminal 3B and start stop unit terminal 1Q
  • Start stop unit malfunction
  • Rear body control module (RBCM) malfunction
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