Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Check Body Integrated Unit Power Supply And Ground Circuit
For the DC power supply circuit, refer to "WIRING DIAGRAMS".
- Impreza model: Ref. to WIRING SYSTEM (IMPREZA MODEL)>POWER SUPPLY CIRCUIT .
- Except for Crosstrek hybrid model: Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>POWER SUPPLY CIRCUIT .
- Crosstrek hybrid model: Ref. to WIRING SYSTEM (CROSSTREK MODEL (HEV))>POWER SUPPLY CIRCUIT .
- Except for Crosstrek hybrid model
- Crosstrek hybrid model
- CHECK DTC
.
- Turn the ignition switch to ON.
- Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to COMMON (DIAG)>DIAGNOSTIC TROUBLE CODE (DTC) .
Is DTC of the power supply system displayed?
Yes: Perform the diagnosis according to the DTC.
No: Go to 2.
- CHECK FUSE
.
- Turn the ignition switch to OFF.
- Check the fuse.
Is the check result OK?
Yes: Go to 3.
No: Replace the defective fuse.
- CHECK HARNESS BETWEEN BODY INTEGRATED UNIT AND BATTERY
.
- Disconnect the body integrated unit connector.
- Turn the ignition switch to ON.
- Measure the voltage between body integrated unit and chassis ground.
Connector & terminal
(B280) No. 1 (+) - Chassis ground (-):
(B287) No. 4 (+) - Chassis ground (-):
Is the voltage 9 - 16 V?
Yes: Go to 4.
No: Repair the open circuit of harness between body integrated unit and battery.
- CHECK BODY INTEGRATED UNIT IGN POWER SUPPLY CIRCUIT
.
- Turn the ignition switch to ON.
- Measure the voltage between F/B fuse No. 5 and chassis ground.
Connector & terminal
F/B fuse No. 5 (+) - Chassis ground (-):
Is the voltage 10 V or more?
Yes: Go to 5.
No: Repair the open circuit of the harness between body integrated unit and ignition switch.
- CHECK BODY INTEGRATED UNIT AND ACC VOLTAGE SUPPLY CIRCUIT
.
- Turn the ignition switch to ACC.
- Measure the voltage between F/B fuse No. 9 and chassis ground.
Connector & terminal
F/B fuse No. 9 (+) - Chassis ground (-):
Is the voltage 10 V or more?
Yes: Go to 6.
No: Repair the open circuit of the harness between body integrated unit and ignition switch.
- CHECK HARNESS BETWEEN BODY INTEGRATED UNIT AND CHASSIS GROUND
.
- Turn the ignition switch to OFF.
- Measure the harness resistance between the body integrated unit and chassis ground.
Connector & terminal
(i84) No. 4 - Chassis ground:
(B287) No. 1 - Chassis ground:
Is the resistance less than 1 Ω?
Yes: Go to 7.
No: Repair the open circuit of harness between the body integrated unit and chassis ground.
- CHECK FOR POOR CONTACT
.
Is there poor contact of connector?
Yes: Repair the poor contact.
No: End.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.