2012 Toyota Prius ThreeFACTORY OEM SERVICE PROCEDURE

Fail-Safe Chart

WARNING: This page is about a different variant/trim than selected.
  1. FAIL-SAFE FUNCTION 
    1. When communication fails in any of the CAN bus wires (communication wires), a fail-safe function(s) will operate. The fail-safe function that is specified for each system operates to prevent those systems from malfunctioning.
    2. The following table shows the effects on each system when communication is impossible. (For further details, see the service information for each system.)
      Function
      (Function Description)      		 Control Master System Related Fail-safe Operation DTC
      (Driver Detectable)
      Power switch
      (Power source control)      		 Power management control ECU
      • Transmission control ECU assembly
      • Brake booster with master cylinder (Skid control ECU)
      • Main body ECU
      • Combination meter assembly
      • Power switch does not change to on (READY) even when power switch is pressed with the brake pedal depressed
      • Power switch off is prohibited
      • A/C does not start using transmitter key or smart phone (mobile phone terminal)
      		 U0129
      U0293
      (Warning and indicator lights come on)
      Collision judgment
      (Judges a collision based on airbag signal (CTD-HV))      		 Power management control ECU Center airbag sensor assembly Only motor operation is used (Engine is not used) U0100
      U0151
      (Warning and indicator lights come on)
      HV system power processing
      (Stores power source DTCs and turns off the power source when the HV system is malfunctioning)      		 Power management control ECU - Normal driving U1107
      (Warning and indicator lights come on)
      Plug-in charging
      (Sends battery information)      		 Plugin charge control ECU assembly Power management control ECU Only motor operation is used (Engine is not used) U0100
      U019B
      (Warning and indicator lights come on)
      Shift position indicator display Transmission control ECU assembly
      • Brake booster with master cylinder (Skid control ECU)
      • Main body ECU
      • Combination meter assembly
      		 Shift position indicator is not displayed U0146
      (Warning and indicator lights come on)
      Regenerative braking control Power management control ECU Brake booster with master cylinder (Skid control ECU) Regenerative braking will stop
      (ABS/VSC control gradually stops)      		 U0073
      U0123
      U0124
      U0126
      U0129
      U0293
      (Warning and indicator lights come on)
      VSC control
      (Controls driving force while VSC operating)      		 Brake booster with master cylinder (Skid control ECU)
      • Power management control ECU
      • Yaw rate and acceleration sensor
      • Steering angle sensor
      		 ABS/VSC control is inoperative
      (ABS/VSC control gradually stops)      		 U0073
      U0123
      U0124
      U0126
      U0293
      (Warning and indicator lights come on)
      ABS control
      (Controls driving force while ABS operating)      		 Brake booster with master cylinder (Skid control ECU) Yaw rate and acceleration sensor ABS control is inoperative
      (ABS control gradually stops)      		 U0073
      U0123
      U0124
      U0126
      U0293
      (Warning and indicator lights come on)
      TRAC control
      (Engine power control by VSC/TRAC)      		 Brake booster with master cylinder (Skid control ECU)
      • Power management control ECU
      • Yaw rate and acceleration sensor
      • Steering angle sensor
      		 ABS/VSC control is inoperative
      (ABS/VSC control gradually stops)      		 U0073
      U0123
      U0124
      U0126
      U0293
      (Warning and indicator lights come on)
      Automatic brake control
      (-Vehicle-to-vehicle distance control brake -Pre-collision brake assist system)      		 Brake booster with master cylinder (Skid control ECU) Driving support ECU Automatic brake control stops U0073
      U0123
      U0124
      U0126
      U0293
      (Warning and indicator lights come on)
      Electric power steering control
      (Speed of vehicle induction type torque control)      		 Power steering ECU assembly
      • Power management control ECU
      • Brake booster with master cylinder (Skid control ECU)
      		 Depression of EPS assist
      (Deterioration of steering assist)      		 U0129
      U0293
      (Warning light comes on)
      Steering/steering angle sensor initialization and zero point learning Power steering ECU assembly
      • Brake booster with master cylinder (Skid control ECU)
      • Steering angle sensor
      • Yaw rate and acceleration sensor
      		 Steering initialization and zero point learning are not performed U0129
      (Warning light comes on)
      Steering assist compensation control
      (Provides steering assist with compensation amount based on vehicle speed)      		 Power steering ECU assembly Brake booster with master cylinder (Skid control ECU) Control is performed based on a default vehicle speed of approximately 100km/h (62 mph) U0129
      (Warning light comes on)
      Air conditioning control
      (Air conditioning control is in cabin)      		 Air conditioning amplifier assembly
      • Power management control ECU
      • ECM
      • Combination meter assembly
      • Main body ECU
      		 Air conditioning function and PTC heater function stop U0100
      U0131
      U0140
      U0142
      U0155
      U0164
      U0293
      (Air conditioning is inoperative)
      A/C start using transmitter key or smart phone (mobile phone terminal)
      • Air conditioning amplifier assembly
      • Main Body ECU
      • Power management control ECU
      • Air conditioning amplifier assembly
      • Main Body ECU
      		 A/C does not start using transmitter key or smart phone (mobile phone terminal) U0140
      U0164
      (None)
      Diagnostic system
      (Receives DTCs from ECUs via CAN communication and blinks the warning lights to indicate the DTCs in the combination meter (or shows a message on the multi-information display))      		 Combination meter assembly
      • Center airbag sensor assembly
      • Brake booster with master cylinder (Skid control ECU)
      • ECM
      • Power steering ECU assembly
      • Driving support ECU
      • Seat belt control ECU
      • Corresponding warning light remains off
      • Mode changes from diagnostic mode to normal mode
      • Airbag warning light illuminates
      • Brake warning light (yellow): The latest signal state is maintained until the power switch is turned off
      • Slip indicator light: The latest signal state is maintained until the power switch is turned off
      • ABS warning light illuminates
      		 U0100
      U0129
      U0131
      U0151
      (None)
      HUD display function
      (Displays intersection guide information of the navigation system on the meter or HUD device)      		 Combination meter assembly Navigation ECU sub-assembly (Navigation receiver assembly)*2 - U0073
      (None)
      Entry function/Power door lock control
      • Certification ECU (Smart key ECU assembly)
      • Main Body ECU
      • Main body ECU
      • ECM
      • Combination meter assembly
      • Power management control ECU
      • Certification ECU (Smart key ECU assembly)
      • Air conditioning amplifier assembly
      • DCM (Telematics transceiver)
      		 Unlock permitted U0100
      U0101
      U0142
      U0151
      U0155
      U0164
      U0198
      U0293
      U0327
      U1133
      (Wireless door lock cannot operate)
      Remote climate control
      (Activates air conditioning system using battery power based on user command)      		 Main Body ECU
      • Power management control ECU
      • Air conditioning amplifier assembly
      • Certification ECU (Smart key ECU assembly)
      • DCM (Telematics transceiver)
      		 Remote climate control does not operate U0101
      U0164
      U0198
      U0293
      U0327
      U1133
      (None)
      Vehicle-to-vehicle distance control Driving support ECU
      • Power management control ECU
      • Brake booster with master cylinder (Skid control ECU)
      • Main body ECU
      • Combination meter assembly
      • Steering angle sensor
      • Yaw rate and acceleration sensor
      		 Vehicle-to-vehicle distance control does not operate U0122
      U0123
      U0126
      U0293
      U1104
      (Warning and indicator lights come on)
      Pre-collision system Driving support ECU
      • Main body ECU
      • Power management control ECU
      • Brake booster with master cylinder (Skid control ECU)
      • Steering angle sensor
      • Yaw rate and acceleration sensor
      • Combination meter assembly
      		 Pre-collision control is inoperative U0122
      U0123
      U0126
      U0293
      U1100
      (Warning and indicator lights come on)
      Seat belt control ECU
      • Brake booster with master cylinder (Skid control ECU)
      • Driving support ECU
      • Center airbag sensor assembly
      • Main body ECU
      		 Pre-collision control is inoperative U0122
      U0140
      U0151
      U1104
      (Warning and indicator lights come on)
      IT cooperative system
      (Performs remote climate control function)      		 DCM (Telematics transceiver)
      • Air conditioning amplifier assembly
      • Power management control ECU
      • Main body ECU
      		 Remote climate control does not operate U0140
      U0164
      U0293
      (None)
      IT cooperative system
      (Performs and checks charging)      		 DCM (Telematics transceiver)
      • Combination meter assembly
      • Plugin charge control ECU assembly
      		 Timer charging and charging check do not operate U1135
      (None)
      IT cooperative system
      (Supports Eco driving)      		 DCM (Telematics transceiver)
      • Brake booster with master cylinder (Skid control ECU)
      • Power management control ECU
      • Combination meter assembly
      • Plugin charge control ECU assembly
      		 Invalid data is sent to the center (Eco information will not be sent) U0129
      U0155
      U0293
      U1135
      (None)
      IT cooperative system
      (Informs driving information)      		 DCM (Telematics transceiver)
      • Power management control ECU
      • Combination meter assembly
      		 Invalid data is sent to the center U0155
      U0293
      (None)
      Navigation Eco display
      (Displays fuel consumption per minute and regeneration amount in chart and displays history of average fuel economy)
      • Navigation ECU sub-assembly (Navigation receiver assembly)*1
      • Radio and display receiver assembly*2
      • Power management control ECU
      • ECM
      • Brake booster with master cylinder (Skid control ECU)
      • Combination meter assembly
      		 On the navigation Eco screen:
      • Update of the per-minute fuel consumption display (per minute fuel consumption calculation) on the navigation Eco screen (per-minute fuel consumption screen) is stopped
      • Update of the current average fuel economy display on the navigation Eco screen (block fuel consumption screen) is stopped
      • If drivable mileage is displayed on the navigation Eco screen (block fuel consumption screen), the numeric part of the drivable mileage disappears because drivable mileage data cannot be received
      		 U0100
      U0155
      U0293
      (None)
      Energy monitor display
      (Creates energy flow screen which indicates regeneration status and drive force transmission status)
      • Navigation ECU sub-assembly (Navigation receiver assembly)*1
      • Radio and display receiver assembly*2
      		 Power management control ECU Energy flow is not displayed U0100
      U0293
      (None)
      Destination identification
      (Identifies destination based on destination and destination package information, and selects the time zone and language used for the display)
      • Navigation ECU sub-assembly (Navigation receiver assembly)*1
      • Radio and display receiver assembly*2
      		 Main body ECU Destination is identified based on information received before communication is interrupted U0140
      (None)
      Vehicle customization function
      (Identifies destination based on destination and destination package information, and selects the time zone and language used for the display)
      • Navigation ECU sub-assembly (Navigation receiver assembly)*1
      • Radio and display receiver assembly*2
      • Certification ECU (Smart key ECU assembly)
      • Air conditioning amplifier assembly
      • Main body ECU
      		 When an application that uses remote communication is activated (customization/ remote diagnosis), the process will be performed regardless of main body ECU remote communication permit/ prohibit state U0073
      (None)
      Rear view monitor control
      (Displays rear view monitor (without guide lines))
      • Navigation ECU sub-assembly (Navigation receiver assembly)*1
      • Radio and display receiver assembly*2
      		 Main body ECU Screen does not change to camera display U0100
      (None)

      HINT: 

      • *1: for Navigation receiver type
      • *2: for Radio and display type
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