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Throttle Body: Prius

WARNING: Read service precautions before proceeding with service procedure. See SERVICE PRECAUTIONS .
  1. Electronic Throttle Control System (ETCS) is used for controlling idle speed. ETCS consists of throttle body, accelerator pedal position sensor, Throttle Position (TP) sensor, throttle control motor, Hybrid Vehicle Control Electronic Control Unit (HV ECU) and Engine Control Module (ECM).
  2. To inspect ETCS operation, ensure ignition is off. Disconnect electrical connector at throttle control motor on throttle body. See Fig 1.
    Fig 1: Locating Electronic Throttle Control System Components On Throttle Body & Accelerator Pedal Position Sensor (Prius)
    G00028691Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  3. To test TP sensor operation, connect Toyota hand-held tester to data link connector No. 3 at driver's side of instrument panel. See Figure. Turn ignition on. Hand-held tester is used to read throttle valve opening which is displayed as a percentage.
  4. Rotate throttle linkage to full throttle while reading throttle valve opening on hand-held tester which is accessed by THROTTLE POS under CURRENT DATA. Throttle valve opening should be at 60 percent or more. If throttle valve opening is at least 60 percent, go to next step. If throttle valve opening is not at least 60 percent, problem may exist in TP sensor, wiring circuit or ECM. Go to step  10 for testing of TP sensor. If necessary to check wiring between ECM and TP sensor, see WIRING DIAGRAMS article. ECM is located behind glove box. For illustration of ECM location, see THEORY & OPERATION article.
  5. Turn ignition off. Reinstall electrical connector at throttle control motor. It is necessary to put transit in inspection mode so engine will run continuously. To put transit in inspection mode, perform the following steps within 60 seconds:
    • Ensure ignition is off and then turn ignition on.
    • Ensure transaxle is in Park and then fully depress accelerator pedal 2 times.
    • Place transaxle in Neutral and then fully depress accelerator pedal 2 times.
    • Place transaxle back in Park and then fully depress accelerator pedal 2 times.
  6. Check that master warning light on instrument cluster at center of instrument panel is flashing to indicate inspection mode operation. See Figure. Master warning light may also be referred to as hybrid system error warning light. Turn ignition switch to START position to start engine. Engine will now start and run continuously.
  7. Warm engine to normal operating temperature. To check charging rate of High Voltage (HV) battery, apply brake and place shift lever in Drive and check that engine shuts off. If engine shuts off, go to next step. If engine does not shut off, charging rate of HV battery may be low. Place shift lever in Park and allow engine to run for a while to charge the HV battery. After engine has ran for a while, place shift lever in Drive and check that engine shuts off. If engine now shuts off, go to next step. If engine does not shut off, it may be necessary to place shift lever in Park and allow engine to run for a while to charge the HV battery.
  8. With engine idling, turn A/C switch to ON and OFF positions while noting engine idle speed. Idle speed should be 950-1050 RPM with A/C switch in OFF position and 1150-1250 RPM with A/C switch in ON position. If idle speed is not as specified, go to next step. If idle speed is as specified, shut engine off. Remove hand-held tester.
  9. To test throttle control motor, disconnect electrical connector for throttle control motor. See Fig 1. Using ohmmeter, check resistance between terminals No. 1 and 2 on electrical connector for throttle control motor. See Fig 2. Resistance should be .3-100.0 ohms at 68°F (20°C). If resistance is within specification, reinstall electrical connector. Go to next step. If resistance is not within specification, replace throttle body with throttle control motor as an assembly. See THROTTLE BODY under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.
  10. To test TP sensor, disconnect electrical connector at TP sensor. See Fig 1. Using ohmmeter, check resistance between terminals E2 and VC on TP sensor. See Fig 3. Resistance should be 1200-3200 ohms at 68°F (20°C). If resistance is within specification, reinstall electrical connector. Go to next step. If resistance is not within specification, replace TP sensor. See THROTTLE BODY under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.
  11. It may be necessary to check accelerator pedal position sensor. See ACCELERATOR PEDAL POSITION SENSOR  under ENGINE SENSORS & SWITCHES. If TP sensor, throttle control motor and accelerator pedal position sensor are okay, but ETCS does not operate properly, it may be necessary to check wiring between ECM and TP sensor, ECM and throttle control motor, ECM and HV ECU. See WIRING DIAGRAMS article. ECM is located behind glove box. HV ECU is located below carpet on floor panel, just below passenger's side of instrument panel. For illustration of ECM location, see THEORY & OPERATION article.
    Fig 2: Identifying Terminals & Testing Throttle Control Motor (Prius)
    G00020847Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    Fig 3: Identifying Terminals & Testing Throttle Position Sensor (Prius)
    G00016725Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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