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 Plug-inFACTORY OEM SERVICE PROCEDURE
Problem Symptoms Table
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.
POWER STEERING SYSTEM
| Symptom | Suspected Area | See |
|---|---|---|
| Heavy steering | Front tires (improperly inflated, unevenly worn) | Refer to INSPECTION |
| Front wheel alignment (incorrect) | Refer to ADJUSTMENT | |
| Front suspension (lower ball joint) | Refer to INSPECTION | |
| Steering post assembly | Refer to INSPECTION | |
| Torque sensor (built into steering post assembly) | - | |
| Power steering motor | - | |
| Speed sensor circuit | Refer to DIAGNOSTIC TROUBLE CODE CHART | |
| Auxiliary battery and power source system | - | |
| Power steering ECU assembly power source voltage and relay | Refer to TERMINALS OF ECU | |
| Power steering ECU assembly | Refer to REMOVAL | |
| Steering effort differs between turning right and left, or steering effort is uneven. | Front tires (improperly inflated, unevenly worn) | Refer to INSPECTION |
| Front wheel alignment (incorrect) | Refer to ADJUSTMENT | |
| Front suspension (lower ball joint) | Refer to INSPECTION | |
| Steering gear assembly | Refer to INSPECTION | |
| Torque sensor (built into steering post assembly) | - | |
| Steering post assembly | Refer to INSPECTION | |
| Power steering motor | - | |
| Power steering ECU assembly | Refer to REMOVAL | |
| While driving, steering effort does not change in accordance with vehicle speed or the steering wheel does not return properly. | Front suspension (lower ball joint) | Refer to INSPECTION |
| Speed sensor circuit | Refer to DIAGNOSTIC TROUBLE CODE CHART | |
| Torque sensor (built into steering post assembly) | - | |
| Power steering motor | - | |
| Power steering ECU assembly | Refer to REMOVAL | |
| CAN communication system | Refer to HOW TO PROCEED WITH TROUBLESHOOTING | |
| A knocking (or clunking) sound occurs when turning the steering wheel back and forth while power steering is operating. | Front suspension (lower ball joint) | Refer to INSPECTION |
| Steering intermediate shaft | - | |
| Power steering ECU assembly | Refer to REMOVAL | |
| Noise occurs when turning the steering wheel during low-speed driving. | Steering gear assembly | Refer to INSPECTION |
| Steering post assembly | Refer to REMOVAL | |
| Friction occurs when turning the steering wheel during low-speed driving. | Power steering motor | - |
| Steering post assembly | Refer to INSPECTION | |
| A high-pitched sound (squeaking) occurs when turning the steering wheel slowly with the vehicle stopped. | Power steering motor | - |
| The steering wheel vibrates and noise occurs when turning the steering wheel from lock to lock with the vehicle stopped. | Steering gear assembly | Refer to INSPECTION |
| Steering post assembly | Refer to INSPECTION | |
| DTCs cannot be output (Terminals TC and CG of the DLC3 are connected) | TC and CG terminal circuit | Refer to TC and CG Terminal Circuit |
| IG power source circuit | Refer to DTC C1551/51: IG Power Supply Voltage Malfunction | |
| Combination meter | Refer to HOW TO PROCEED WITH TROUBLESHOOTING | |
| Sensor check cannot be done (Terminals TS and CG of the DLC3 are connected) | TS and CG terminal circuit | Refer to TS and CG Terminal Circuit |
| Power steering ECU assembly | Refer to REMOVAL | |
| EPS warning light remains on. | EPS warning light circuit | Refer to EPS Warning Light Circuit |
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.