LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Mazda >> 2019 >> CX-9 Signature >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Communication Devices >> On-Board Diagnostic - Front Body Control Module (FBCM) >> DTC B1C84-14: Rear Window Defogger Relay Circuit Malfunction [Front Body Control Module (FBCM)] >> Diagnostic Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnostic Procedure

DTC B1C84:14 [FRONT BODY CONTROL MODULE (FBCM)] DIAGNOSTIC PROCEDURE

Step Inspection Action
1 VERIFY FRONT BODY CONTROL MODULE (FBCM) DTCs AGAIN Yes Go to the next step.
No Go to Step 7.
2 INSPECT REAR WINDOW DEFOGGER RELAY Yes Go to the next step.
No Replace the rear window defogger relay, then go to Step 6.
(See RELAY LOCATION .)
3 INSPECT FRONT BODY CONTROL MODULE (FBCM) CONNECTOR CONDITION
  • Disconnect the front body control module (FBCM) 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 6.
4 INSPECT REAR WINDOW DEFOGGER RELAY CONTROL CIRCUIT FOR SHORT TO GROUND
  • Verify that the rear window defogger relay is removed.
  • Verify that the front body control module (FBCM) connector is disconnected.
  • Inspect for continuity between front body control module (FBCM) terminal 1P (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 window defogger relay terminal E and front body control module (FBCM) terminal 1P.
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 6.
No Go to the next step.
5 INSPECT REAR WINDOW DEFOGGER RELAY CONTROL CIRCUIT FOR OPEN CIRCUIT
  • Verify that the rear window defogger relay is removed.
  • Verify that the front body control module (FBCM) connector is disconnected.
  • Inspect for continuity between rear window defogger relay terminal E (wiring harness-side) and front body control module (FBCM) terminal 1P (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 window defogger relay terminal E and front body control module (FBCM) terminal 1P.
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 the next step.
6 VERIFY THAT REPAIRS HAVE BEEN COMPLETED Yes Repeat the inspection from Step 1.
Go to the next step.
No Go to the next step.
7 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 [FRONT BODY CONTROL MODULE (FBCM)] .)
No DTC troubleshooting completed.