2. OBJECTIVES After studying Chapter 12, the reader should be able to:. 1
OBJECTIVES After studying Chapter 12, the reader should be able to: 1. Identify a Toyota/Lexus hybrid electric vehicle Explain the operation of the various unique systems found in Toyota/Lexus hybrid-electric vehicles List the procedures necessary to disable the high-voltage circuits in Toyota/Lexus hybrid electric vehicles Describe how to safely perform routine service on a Toyota/Lexus hybrid electric vehicle.

3. TOYOTA PRIUS The Prius was first released in Japan in December of 1997 as a 1998 model year. The second-generation Toyota Prius was released in 2003 as a 2004 model.

4. The second-generation Prius was equipped with Hybrid Synergy Drive
The second-generation Prius was equipped with Hybrid Synergy Drive. Both generations of the Toyota Prius use a 1.5-liter inline four-cylinder engine that uses the Atkinson cycle to maximize fuel efficiency.

5. Overall view of the components and their location in a second- generation Toyota Prius.

6. Dash Display The dashboard on the Prius is mostly digital readouts and icons. There is no tachometer, just a temperature gauge and a fuel level gauge. Near the speedometer is a “READY” light.

7. Master Warning Light Note the triangle-shaped indicator with the exclamation mark in the middle. This is known as the master warning light.

8. Energy Monitor The energy monitor is one of the views available on the large multidisplay.

9. Consumption screen also shows the average fuel economy over each 5-minute period up to 30 minutes of history.

10. Smart Entry and Start Electronic Key (Optional Equipment) The second-generation Prius may be equipped with an optional smart entry and start electronic key that appears similar in function and design to the standard electronic key.

11. Smart key features include: Passive (remote) function to lock/unlock the doors and start the vehicle Wireless transmitter to lock/unlock the doors Electronic key for starting Hidden metal cut key to lock/unlock the doors from the driver door lock Be sure to keep the smart key at least 15 feet from the vehicle when performing repair procedures. This provides an added margin of safety as it will prevent inadvertent starting of the vehicle because the normal range is 10 feet.

12. When B is selected, the transmission allows the ICE to operate at a higher RPM, causing it to absorb more of the vehicle’s kinetic energy than it would at lower RPMs. Drivers looking for the best fuel mileage should not shift into B unless descending a long, steep grade.

13. Park on a second-generation Prius is a button rather than a position on the gear selector.

14. “By-Wire” Technology Numerous systems on the Prius have been designed to incorporate by-wire technology.

15. Brake-by-wire. The brake system on the Prius includes a stroke simulator that provides a normal pedal stroke during regenerative braking. There is also a power source backup unit (second-generation Prius) located next to the auxiliary battery that provides electrical power to the brake system if the 12-volt battery is damaged or disconnected.

16. Electronic throttle control
Electronic throttle control. The mechanical linkage between the ICE throttle body and the accelerator pedal has been eliminated in favor of electronic control.

17. Shift-by-wire. A special electronic sensor that responds to both lateral and vertical movement is used as the driver’s shift selector.

18. Shift control actuator
Shift control actuator. The only mechanical shifting that takes place in a Prius transmission is the operation of the parking lock mechanism.

19. Driving a Toyota Hybrid electric Vehicle Turning the key ( Prius) to the crank position will cause the ICE to start when the “READY” light illuminates or shortly thereafter. If the ICE is already warmed up, the “READY” light will illuminate and the ICE will not start. When the “READY” light is lit, the vehicle is ready to drive, whether the ICE is running or not.

20. While depressing the brake pedal, press the POWER button once and Prius will go straight to READY mode.

21. COLD-START EMISSION CONTROLS HC Adsorber and Catalyst ( Prius Only) When a catalytic converter is cold, it cannot oxidize HC and CO. The HC Adsorber and Catalyst (HCAC) system utilizes a special catalytic converter assembly that incorporates an HC adsorber to trap and store unburned hydrocarbons during cold starts. Once the catalytic converter is up to operating (light off) temperature, the HCAC bypass valve is opened and HC is purged and sent through the hot catalyst. The bypass valve is also closed during deceleration to purge any remaining HC from the adsorber.

23. Coolant Heat Storage System (2004 and Later Prius Only) The second-generation Prius did not use the HCAC system. A coolant heat storage system in which heated coolant is stored in a specially designed tank during normal vehicle operation and is then used to warm the engine intake ports prior to a cold start. Warming the intake ports and cylinder head before a cold start helps start the ICE more quickly and reduces HC and CO emissions.

24. FUEL SYSTEM COMPONENTS In order to receive certification as a AT-PZEV vehicle, very strict evaporative emission standards must be met.

25. Bladder Fuel Tank Both generations of the Prius utilize a bladder fuel tank, which stores the fuel in a resin bladder enclosed in a steel shell. The resin bladder can expand and contract with the fuel. Fuel level calculations are based on inputs from a fuel gauge sender and ambient temperature sensor (both located in the tank) plus data from two inclination sensors mounted in the combination meter ECU.

27. Closed Fuel Tank System The closed fuel tank system is only used on the Highlander hybrid and Lexus RX400h models. A tank close valve (also called a vapor-containment valve) is used to seal the tank and control vapor flow during purge and refueling. An electric fuel door prevents the fuel cap from being removed until the tank pressure has been bled through the charcoal canister and the system is ready for refueling. During this process, the multi-information display reads “PLEASE WAIT NOW OPENING.” When the system has finished depressurizing, it unlocks the fuel door and the display shows “REFUEL READY.”

28. HIGH-VOLTAGE BATTERY PACK Each NiMH cell produces 1
HIGH-VOLTAGE BATTERY PACK Each NiMH cell produces 1.2 volts; therefore, one module equals 7.2 volts. For the first-generation Prius, 38 modules were installed in series producing volts.

29. Toyota HV Battery Specifications
Vehicle Models
Battery Construction
Raw Battery Weight
Battery Assembly Weight
Prius
1.2-volt cells in banks of 6 × 38 modules = volts
93 lbs (42 kg)
115 lbs (19 kg)
2004 and later Prius
1.2-volt cells in banks of 6 × 28 modules = volts
64 lbs (29 kg)
86 lbs (39 kg)
Highlander Hybrid Lexus RX400h
1.2-volt cells in banks of 8 × 30 modules = volts
100 lbs (45 kg)
152 lbs (69 kg)
Camry Hybrid
1.2 volt cells in banks of 6 × 34 modules = volts
n/a
Lexus GS450h
1.2 volt cells in banks of 6 × 40 modules = 288 volts

30. A first-generation Prius battery pack contains 38 modules, wiring, a system main relay (SMR), computer, a manual disconnect service plug, and a strong metal box to contain everything.

31. HV Battery Cooling The high-voltage battery pack is air cooled and utilizes a fan and ducting in the rear of the vehicle for circulating cabin air through the battery assembly. The cooling air can exit outside the vehicle or inside depending on the air pressure in the vehicle cabin.

32. HV Battery Diagnosis and Service The warranty of the battery pack varies by manufacturer but typically is covered for eight years or 100,000 miles. Environmental concerns regarding battery disposal were addressed prior to releasing hybrids in the United States by requiring a “cradle-to-grave” process. An 800 telephone number is located on the battery case or under the hood, and this number should be called when an end-of-life NiMH battery assembly needs to be recycled.

33. Replacing the HV Battery Pack When replacing a battery pack, the entire box is replaced as a unit. It weighs about 115 lbs (52 kg) and should be handled carefully as high voltage is contained inside. The high-voltage battery system must be disabled before attempting any system repairs. Be sure to wear the appropriate personal protective equipment (PPE) and follow the manufacturer-specified procedures.

34. THE TOYOTA HYBRID SYSTEM The Toyota Hybrid System (THS), as used in both generations of the Prius, consists of one planetary gearset and two electric machines. The planetary gearset is known as a power-split device, because it splits power from the ICE and uses it for moving the vehicle and for generating electrical power.

35. One electric machine is attached to the planetary sun gear and is called motor-generator 1 (abbreviated MG1). The second electric machine is attached to the planetary ring gear and is labeled motor-generator 2 (abbreviated MG2). The ICE is also connected to the planetary gearset through the planet carrier.

36. During operation, each motor-generator fulfills two primary functions: MG1 is used to start the internal combustion engine and generate electricity for charging the high-voltage batteries, as well as driving MG2. MG2 is used to propel the vehicle and generate electricity during slowing and braking (regenerative braking). MG2 is connected directly to the drive wheels at all times.

37. Four-wheel-drive versions of the Highlander Hybrid and Lexus RX400h use a third electric machine known as MGR. MGR is connected to the rear wheels and is used to propel the vehicle forward and backward as well as for regenerative braking.

38. Inverter Assembly Control of the motor-generators in the Toyota Hybrid System is accomplished using the inverter assembly located in the ICE compartment.

39. 1. Inverter. Converts high-voltage DC into three-phase AC to power MG1, MG2, and MGR. 2. DC-DC converter. Converts high-voltage DC to 12-VDC to power the vehicle auxiliary systems. 3. Boost converter. 4. A/C compressor inverter. 5. Cooling system.

40. LEXUS RX400h/TOYOTA HIGHLANDER HYBRID The Lexus RX400h is a strong hybrid, which means that it is capable of operating in electric-only or gas-engine-only mode, as well as a mode that combines the power of the gas engine and electric motor.

41. The hybrid system uses a 288-volt DC nickel metal hydride (Ni-MH) battery pack that is located under the rear seat.

42. The battery power is directed through a boost converter that raises the voltage to 650 volts DC. An inverter changes this to 650 volts AC for use by a front-mounted 123-kW electric motor that turns as high as 12,400 RPM.

43. The RX 400h four-wheel drive (4WD) system uses a separate 50-kW electric motor (MGR) at the rear that provides up to 96 lb-ft of additional drive torque. MGR is integrated into the rear-drive unit with a differential in an independent rear suspension configuration. The system electronically varies front and rear torque distribution depending on traction conditions.

44. Vehicle Dynamic Integrated Management (VDIM) VDIM also interfaces with the Electronic Throttle Control (ETC) system and the Electronic Power Steering (EPS) system to optimize steering assist for each situation.

45. The EPS uses a brushless-type DC motor and gear reduction system built into the steering gear housing to provide steering assist.

46. Driving the RX 400h All of the comfort and luxury found inside the RX 330 is present in the RX 400h, with a few changes, including: In place of a traditional tachometer, the RX 400h has a power meter that displays the level of power generated by the hybrid power train. The driver can also monitor the gas-electric power distribution on the multi-information display or on the optional navigation system's 7-inch touch-panel display screen.

47. TOYOTA CAMRY HYBRID The Toyota Camry Hybrid features a 2
TOYOTA CAMRY HYBRID The Toyota Camry Hybrid features a 2.4-liter inline four-cylinder ICE using the Atkinson cycle. The Camry Hybrid is a front-wheel-drive THS II configuration. The package includes a 105-kW electric motor and a high-voltage battery pack that delivers a peak of 45 hp.

48. The high-voltage battery pack produces 244 volts and consists of 34 nickel metal hydride modules, each of which contains six 1.2-volt cells. The battery pack is located behind the rear passenger seat backs.

49. The 12-volt auxiliary battery is located on the passenger side of the trunk area. The inverter assembly incorporates a boost converter that raises the 244 volts DC from the battery pack to 650 volts DC for higher motor efficiency.

50. LEXUS GS450h The Lexus GS450h is a rear-wheel-drive sedan using a V-6 ICE and a Hybrid Synergy Drive transmission. The transmission incorporates a power-split planetary gear unit along with a two-stage motor speed reduction planetary. The second planetary can switch between two ranges and will vary the speed of MG2 according to vehicle speed and torque requirements.

51. MAINTENANCE AND SERVICE PROCEDURES Care should be taken when driving a Toyota/Lexus hybrid in and around the shop because they can be driven using electric power only. Known as stealth or quiet mode, this means that the vehicle can be moving yet no sound will be heard. The ICE can start anytime the READY indicator is illuminated. Be sure that the READY light is out before performing any vehicle service.

52. Disabling the High-Voltage System The following steps must be performed prior to servicing the high-voltage system on a Toyota hybrid electric vehicle: 1. Turn the ignition system OFF. 2. Disconnect the negative battery cable from the auxiliary battery. 3. While wearing high-voltage linesman’s gloves with leather outer gloves, remove the orange service plug. 4. Take steps to make sure that the service plug cannot be installed by another service technician while you are servicing the vehicle. This can be done by securing the service plug on your person or in a special lock box. 5. After removing the service plug, wait five minutes before touching any part of the high-voltage system. Verify that the system is de-energized by measuring system voltage with a digital multimeter (DMM).

55. The 2004 and later Prius has a service plug that requires two steps to properly reinstall it in the battery pack connector. The handle (lever) on the plug must be rotated to the right as the plug is being installed.

56. Testing for Proper Insulation The Toyota Hybrid System monitors the voltage on the body and will disconnect the high-voltage source if a fault is indicated.

57. A special tester, such as the Fluke model 1587, is required to test if any of the high- voltage circuits are making contact with the body or ground of the vehicle.

58. Scan Tool. While some aftermarket scan tools can access hybrid PIDs and DTCs and perform some bi-directional tests, there is nothing that outperforms the factory scan tool for the specific vehicle. Toyota’s Diagnostic Tester will access all available vehicle information and perform all diagnostic testing on the Toyota Hybrid System.

59. Rubber gloves were used to remove the large orange service plug.

60. Routine Service The CVT requires periodic transmission fluid replacement. Be sure to use the factory- recommended fluid. Also, check the fluid level of the inverter coolant as it provides cooling for the ATF as well. The first-generation Prius used Toyota’s Long Life Coolant, which was red in color.

61. SUMMARY 1. The first-generation Prius was introduced in 2001 in the United States and the second generation was released in 2003 as a 2004 model The Prius engine uses the Atkinson cycle and displaces 1.5 liters. 3. The THS inverter is cooled by the same heat exchanger as the transaxle. 4. The Prius is ready to be driven when the READY light is on steady (steady ready). 5. The high-voltage battery packs on Toyota hybrids are air cooled using vents on the outside or alongside the rear seat The Lexus RX400h has an optional rear motor, giving the vehicle four-wheel-drive capability. 7. Care should be taken when driving a Toyota hybrid in parking lots or at slow speeds in or around the shop because it operates on battery power alone under these conditions and others may not hear the vehicle approach.

62. REVIEW QUESTIONS 1. What is unique about starting a Prius. 2
REVIEW QUESTIONS 1. What is unique about starting a Prius? 2. What are the functions of the inverter in a Toyota HEV? 3. What is the procedure for disconnecting the high-voltage circuits on a Toyota HEV? 4. What are the precautions when working on Toyota hybrid vehicles?