PRECAUTION
- HANDLING PRECAUTIONS FOR SRS AIRBAG SYSTEM (SEE «PRECAUTION»(ref-307039-S34846330152008123100000) ) NOTE: Some service operations affect the SRS airbag. Be sure to read the precautionary notice for the SRS airbag before servicing.
- PRECAUTIONS FOR REMOVAL, INSTALLATION AND REPLACEMENT OF ELECTRONIC MOTOR POWER STEERING COMPONENTS Be sure to align the front wheels straight ahead when removing and installing the steering gear assembly. When disconnecting the sliding yoke of the steering column and the pinion shaft of the steering gear assembly, be sure to put matchmarks before starting the operation. When any component related to the steering system has been removed and either reinstalled or replaced, perform the steering center point adjustment (zero point calibration) (see «TERMINALS OF ECU»(ref-307039-S35667293012008123100000) ). When disconnecting the connector related to the electronic motor power steering wheel, turn the power switch ON (IG) (the engine and the hybrid system are not stopped), center the steering wheel, turn the power switch OFF, and then disconnect the connector. When reconnecting the connector related to the electronic motor power steering system, ensure that the power switch is OFF. Center the steering wheel and then turn the power switch ON (IG) (the engine and the hybrid system are not stopped). NOTE: Do not turn the power switch ON (IG) (the engine and the hybrid system are not stopped) when the steering wheel is not centered. If the procedures above are not performed out properly, the steering center point (zero point) will deviate, which may lead to a difference in steering effort between right and left. If there is a difference in steering effort between right and left, perform the steering center point adjustment (zero point calibration) (see «TERMINALS OF ECU»(ref-307039-S35667293012008123100000) ). NOTE: FOR INITIALIZATION When disconnecting the cable from the negative (-) battery terminal, initialize the following systems after the cable is reconnected. SYSTEM REFERENCE System Name Reference Power Window Control System «INITIALIZATION»(ref-289861-S01642846932008070800000) NOTE: FOR HYBRID SYSTEM ACTIVATION When the warning light is illuminated or the battery has been disconnected and reconnected, pressing the power switch may not start the system on the first try. If so, press the power switch again. With the power switch's power mode changed to ON (IG), disconnect the battery. If the key is not in the key slot during reconnection, DTC B2799 may be output.
Scheme 44
- A rack and pinion type steering gear is used on all models.
- The PRIUS uses a vehicle-speed sensing type EPS (Electric Power Steering) on all models.
- FOR INITIALIZATION NOTE: When disconnecting the cable from the negative (-) battery terminal, initialize the following systems after the cable is reconnected. SYSTEM REFERENCE System Name See procedure Power Window Control System «INITIALIZATION»(ref-289861-S01642846932008070800000)
- FOR HYBRID SYSTEM ACTIVATION NOTE: When the warning light is illuminated or the battery has been disconnected and reconnected, pressing the power switch may not start the system on the first try. If so, press the power switch again. With the power switch's power mode changed to ON (IG), disconnect the battery. If the key is not in the key slot during reconnection, DTC B2799 may be output.
- HANDLING PRECAUTIONS When handling the electronic parts: Avoid any impact to electronic parts such as ECUs and relays. Replace the parts with new ones if dropped or subjected to a severe impact. Do not expose any electronic parts to high temperature and humidity. Do not touch the connector terminals in order to prevent deformation or malfunctions due to static electricity. When the power steering ECU has been replaced with a new one, perform the torque sensor zero point calibration (see «CALIBRATION»(ref-289882-S08061411722008070800000) ). When handling the steering column: Avoid any impact to the steering column, especially to the motor or torque sensor. Replace the parts with new ones if dropped or subjected to a severe impact. Do not pull on the wire harness when moving the steering column. When the steering column has been replaced, perform the torque sensor zero point calibration after initializing the torque sensor zero point calibration signal (see «CALIBRATION»(ref-289882-S08061411722008070800000) ). When disconnecting and reconnecting the connectors: When disconnecting a connector related to the electric power steering system, turn the power switch ON (IG), center the steering wheel, turn the power switch OFF, and then disconnect the connector. When reconnecting a connector related to the electric power steering system, ensure that the power switch is OFF. Center the steering wheel and then turn the power switch ON (IG). NOTE: Do not turn the power switch ON (IG) when the steering wheel is not centered. If the above operations are not carried out properly, the steering center point (zero point) will deviate, which may lead to a difference in right and left steering effort. If there is a difference in right and left steering effort, perform the torque sensor zero point calibration (see «CALIBRATION»(ref-289882-S08061411722008070800000) ).
- PRECAUTIONS FOR CAN COMMUNICATION CAN communication is used to receive information from the skid control ECU and to transmit warnings to the meter and the multi-display. When there are any problems in the CAN communication lines, DTCs indicating the communication line malfunctions are output. Perform troubleshooting for the communication line problems when the CAN communication DTCs are output. Be sure to start troubleshooting on the electronic power steering system when data communication is normal. A temporary fix or repair with bypass wiring, etc. is impossible because the length and path of each CAN communication line is specific.
Scheme 45
Scheme 46
Scheme 47
FREEZE FRAME DATA
Note. It is difficult to show the specified values (judgment values) clearly because freeze frame data values significantly change due to differences in measurement conditions, surroundings or vehicle conditions. Because of this reason, there may be a problem even when the values are within specifications. Turn the power switch ON (IG) and park the vehicle on level ground to check the freeze frame data using the Techstream.
- Connect the Techstream (with CAN VIM) to the DLC3.
- Turn the power switch ON (IG).
- Turn the Techstream on.
- Check the freeze frame data. Enter the following menus: Chassis / EMPS / Utility / Freeze Frame Data.
EMPS
| Tester Display | Item Description / Range | Inspection Condition | Reference Value |
|---|---|---|---|
| Torque Sensor 1 Output | Torque sensor 1 output value / min.: 0 V, max.: 5 V | Steering wheel is not turned (without load) | 2.3 to 2.7 V |
| Turning steering wheel to right with vehicle stopped | 2.5 to 4.7 V | ||
| Turning steering wheel to left with vehicle stopped | 0.3 to 2.5 V | ||
| Torque Sensor 2 Output | Torque sensor 2 output value / min.: 0 V, max.: 5 V | Steering wheel is not turned (without load) | 2.3 to 2.7 V |
| Turning steering wheel to right with vehicle stopped | 2.5 to 4.7 V | ||
| Turning steering wheel to left with vehicle stopped | 0.3 to 2.5 V | ||
| Torque Sensor 3 Output | Torque value for assist control / min.: 0 V, max.: 5 V | Steering wheel is not turned (without load) | 2.3 to 2.7 V |
| Turning steering wheel to right with vehicle stopped | 2.5 to 4.7 V | ||
| Turning steering wheel to left with vehicle stopped | 0.3 to 2.5 V | ||
| Meter Vehicle Velocity | Vehicle speed from meter / min.: 0 km/h, max.: 255 km/h | Vehicle is stopped | 0 km/h |
| Vehicle is driven at a constant speed | No significant fluctuation | ||
| MOTOR ACTUAL CURRENT | Amount of current to motor / min.: -128 A, max.: 127 A | ||
| COMMAND VALUE CURRENT | Demanded amount of current to motor / min.: -128 A, max.: 127 A | ||
| THERMISTOR TEMP | ECU substrate temperature / min.: -50°C, max.: 205°C | Power switch is ON (IG) | |
| PIG POWER SUPPLY | Power source voltage to activate motor / min.: 0 V, max.: 25.5 V | Power steering is in operation | 10 to 16 V |
| IG POWER SUPPLY | ECU power source voltage / min.: 0 V, max.: 25.5 V | 10 to 16 V | |
| TRQ1 ZERO POINT VALUE | Zero point value of torque sensor 1 / min.: 0 V, max.: 5 V | Steering wheel is not turned (without load) | 2.3 to 2.7 V |
| TRQ2 ZERO POINT VALUE | Zero point value of torque sensor 2 / min.: 0 V, max.: 5 V | Steering wheel is not turned (without load) | 2.3 to 2.7 V |
| TRQ3 ZERO POINT VALUE | Zero point value of torque sensor for assist control / min.: 0 V, max.: 5 V | Steering wheel is not turned (without load) | 2.3 to 2.7 V |
| MTR TERMINAL VOLT(+) | Motor terminal M1 voltage / min.: 0 V, max.: 25.5 V | Turning steering wheel to right | 10 to 16 V |
| Turning steering wheel to left | Below 1 V | ||
| MTR TERMINAL VOLT(-) | Motor terminal M2 voltage / min.: 0 V, max.: 25.5 V | Turning steering wheel to right | Below 1 V |
| Turning steering wheel to left | 10 to 16 V | ||
| READY STATUS | HV system "READY or OFF" | HV system "READY" | READY |
| HV system not "READY" | OFF |
FREEZE FRAME DATA
FAIL-SAFE CHART
When a problem occurs in the electronic motor power steering system, the P/S warning is indicated on the multi-display, the master warning light on the combination meter comes on, and steering power assist is stopped, fixed at a particular point, or decreased simultaneously to protect the system.
Electronic power steering system
| DTC No. | Malfunction | Fail-safe |
|---|---|---|
| C1511 C1512 C1513 C1514 C1517 | Torque sensor malfunction | Power assist stops. |
| C1524 | Motor malfunction | Power assist stops. |
| C1531 C1532 | Power steering ECU malfunction | Power assist stops. |
| C1533 | Temperature sensor malfunction in power steering ECU | Amount of power assist is limited. |
| C1551 | IG power source voltage error | Power assist stops. |
| C1552 | PIG power source voltage error | Power assist stops. |
| C1554 | Power source relay malfunction | Power assist stops. |
| C1555 | Motor relay malfunction | Power assist stops. |
| U0073 | CAN bus malfunction | Amount of power assist is fixed for a speed of 43 mph (70 km/h). |
| U0121 | Skid control ECU communication error | Amount of power assist is fixed for a speed of 43 mph (70 km/h). |
| Extremely high temperature in ECU | Amount of power assist is limited until ECU temperature goes down. | |
| Power source voltage drop | Power assist is interrupted, but normal power assist is resumed when voltage returns. |
FAIL-SAFE CHART
HINT
Amount of power assist may be decreased to prevent the motor and ECUs from overheating if the steering wheel is continuously turned when the vehicle is either stopped or driven at a low speed, or if the steering wheel is kept at either full lock position for a long time. In that case, the amount of power assist returns to normal if the steering wheel is not turned for approximately 10 minutes with the engine idling.