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.
DTC C1B0D Solenoid Valve Sub Relay Circuit
DTC detecting condition:
- When the vehicle's state is READY ON: When IG1 terminal voltage is 9.5 V or more and the solenoid valve sub relay is commanded ON, the relay contact is in OFF state (BS terminal voltage is less than 3.5 V), and this condition continues for 0.2 seconds or more.
- When the vehicle's state is READY OFF: When the solenoid valve sub relay is commanded ON, the relay contact is in OFF state (BS terminal voltage is less than 3.5 V), and this condition continues for 0.2 seconds or more.
Trouble symptom:
Brake warning light illuminates.
Wiring diagram:
Electronic controlled brake system Ref. to WIRING SYSTEM (CROSSTREK MODEL (HEV))>ELECTRIC CONTROL BRAKE SYSTEM .
If DTC C1C20 or C1C21 is detected together with DTC C1B0D, perform diagnosis of C1C20 or C1C21 first.
- CHECK CONNECTOR
.
Check the connecting condition of the EBB control module connector.
Is there looseness, deformation, or corrosion at the connectors?
Yes: Repair or replace the connector.
No: Go to 2.
- CHECK EBB CONTROL MODULE
.
- Turn the ignition switch to OFF.
- Disconnect the EBB control module connector.
- Measure the voltage between EBB control module connector and chassis ground.
Connector & terminal
(AD82) No. 10 (+) - Chassis ground (-):
Is the voltage 11 - 14 V?
Yes: Go to 3.
No: Repair or replace the harness.
- CHECK DTC
.
- Connect the EBB control module connector.
- Using the Subaru Select Monitor, perform the clear memory of [Electric Brake Booster]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
- Turn the ignition switch to OFF.
- With READY ON, perform a driving test.
- Read the DTC of [Electric Brake Booster] using the Subaru Select Monitor. Ref. to ELECTRIC BRAKE BOOSTER (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
Is DTC C1B0D displayed?
Yes: Replace the brake booster assembly (with the master cylinder). Ref. to BRAKE>BRAKE BOOSTER .
No: Currently, it is normal. There may have been a temporary poor contact in the harness and connector or a temporary noise interference.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.