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.
2012 Toyota Prius TwoFACTORY OEM SERVICE PROCEDURE
Problem Symptoms Table
WARNING: This page is about a different variant/trim than selected.
HINT:
- Use the table below to help determine the cause of problem symptoms. If multiple suspected areas are listed, the potential causes of the symptoms are listed in order of probability in the "Suspected Area" column of the table. Check each symptom by checking the suspected areas in the order they are listed. Replace parts as necessary.
- Inspect the fuses and relays related to this system before inspecting the suspected areas below.
PRE-COLLISION SYSTEM
| Symptom | Suspected Area | See |
|---|---|---|
| "CHECK PCS SYSTEM" is displayed | Combination meter | Refer to REMOVAL |
| Seat belt control ECU | Refer to REMOVAL | |
| Driving support ECU | Refer to REMOVAL | |
| "PCS NOT CURRENTLY AVAILABLE" is displayed | System determines wave radar sensor cannot detect obstacles due to bad weather. If weather recovers, normal control returns. (Bad weather history can be checked using Data List.) | Refer to SYSTEM DESCRIPTION |
| Overheating protection fail-safe of seat belt control ECU operates. If ECU temperature drops, normal control returns. | - | |
| Millimeter wave radar sensor | Refer to REMOVAL | |
| Seat belt control ECU | Refer to REMOVAL | |
| Driving support ECU | Refer to REMOVAL | |
| Although there is possibility of collision, pre-collision control (all front collision controls) do not operate ("PCS NOT CURRENTLY AVAILABLE" is not displayed) | Vehicle condition/environment does not match pre-collision control operation conditions (Confirm control operation conditions) | Refer to SYSTEM DESCRIPTION |
| Check installation condition of millimeter wave radar sensor | Refer to INSTALLATION | |
| Perform millimeter wave radar sensor adjustment | Refer to ADJUSTMENT | |
| Millimeter wave radar sensor | Refer to REMOVAL | |
| Seat belt control ECU | Refer to REMOVAL | |
| Driving support ECU | Refer to REMOVAL | |
| Although there is no possibility of collision, pre-collision control (all front collision controls) operates | Vehicle condition/environment does not match pre-collision control operation conditions (Confirm control operation conditions) | Refer to SYSTEM DESCRIPTION |
| Check installation condition of millimeter wave radar sensor | Refer to INSTALLATION | |
| Perform millimeter wave radar sensor adjustment | Refer to ADJUSTMENT | |
| Millimeter wave radar sensor | Refer to REMOVAL | |
| Seat belt control ECU | Refer to REMOVAL | |
| Driving support ECU | Refer to REMOVAL | |
| Neither normal system code nor DTC is output | Power source circuit | Refer to Power Source Circuit |
| Seat belt control ECU | Refer to REMOVAL | |
| Driving support ECU | Refer to REMOVAL | |
| System does not operate normally even when normal system code is output and DTCs are not output | Power source circuit | Refer to Power Source Circuit |
| Seat belt control ECU | Refer to REMOVAL | |
| Driving support ECU | Refer to REMOVAL | |
| Only pre-collision seat belt does not operate | Buckle switch error (malfunction in which DTC is not output) | - |
| Seat belt control ECU | Refer to REMOVAL | |
| Only pre-collision brake does not operate | Pre-collision system cancel switch | Refer to INSPECTION |
| Pre-collision system cancel switch circuit | Refer to Pre-Collision Brake Cancel Switch Circuit | |
| Driving support ECU | Refer to REMOVAL |
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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