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.
2021 Toyota Prius LE AWD-eFACTORY OEM SERVICE PROCEDURE
Occupant Classification System
OCCUPANT CLASSIFICATION SYSTEM DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION [11/2015 - 12/2018]
| DTC Code | Description |
|---|---|
| B1771 | Passenger Side Buckle Switch Circuit Malfunction |
| B1780 | Front Occupant Classification Sensor LH Circuit Malfunction |
| B1782 | Rear Occupant Classification Sensor LH Circuit Malfunction |
| B1785 | Front Occupant Classification Sensor LH Collision Detection |
| B1787 | Rear Occupant Classification Sensor LH Collision Detection |
| B1795 | Occupant Classification ECU Malfunction |
| B1798 | Yaw Rate Sensor Module Malfunction |
| B1799 | Vehicle Stability Control ECU Malfunction |
| U0125 | Lost Communication with Multi-axis Acceleration Sensor Module |
| U0129 | Lost Communication with Brake System Control Module |
OCCUPANT CLASSIFICATION SYSTEM DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION [12/2018 -]
| DTC Code | Description |
|---|---|
| B1771 | Passenger Side Buckle Switch Circuit Malfunction |
| B1780 | Front Occupant Classification Sensor LH Circuit Malfunction |
| B1782 | Rear Occupant Classification Sensor LH Circuit Malfunction |
| B1785 | Front Occupant Classification Sensor LH Collision Detection |
| B1787 | Rear Occupant Classification Sensor LH Collision Detection |
| B1795 | Occupant Classification ECU Malfunction |
| B1798 | Yaw Rate Sensor Module Malfunction |
| B1799 | Vehicle Stability Control ECU Malfunction |
| U0125 | Lost Communication with Multi-axis Acceleration Sensor Module |
| U0129 | Lost Communication with Brake System Control Module |
Factory Service Tools
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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.
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