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Home >> Toyota >> 2021 >> 4Runner TRD Pro >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Cruise Control Systems >> Dynamic Radar Cruise Control System - Diagnostic Codes & Circuit Tests >> Dynamic Radar Cruise Control System >> DTC U0100: Lost Communication with ECM / PCM "A"; DTC U0104: Lost Communication with Cruise Control Module; DTC U0122: Lost Communication with Vehicle Dynamics Control Module; DTC U0125: Lost Communication with Yaw Rate Sensor Module; DTC U0126: Lost Communication with Steering Angle Sensor Module; DTC U0129: Lost Communication with Brake System Control Module [08/2019 - ] >> Description
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DTC U0100: Lost Communication with ECM / PCM "A"; DTC U0104: Lost Communication with Cruise Control Module; DTC U0122: Lost Communication with Vehicle Dynamics Control Module; DTC U0125: Lost Communication with Yaw Rate Sensor Module; DTC U0126: Lost Communication with Steering Angle Sensor Module; DTC U0129: Lost Communication with Brake System Control Module [08/2019 - ]: Description

The millimeter wave radar sensor assembly and ECM communicate with each sensor and ECU via CAN communication.

If any malfunction is detected in a CAN communication circuit, one or more CAN communication system DTCs are stored.

DTC No. Detection Item DTC Detection Condition Trouble Area
U0100 Lost Communication with ECM / PCM "A" Condition 1: 
  • While the vehicle speed is 36 km/h (22 mph) or more and the dynamic radar cruise control system is operating, a communication error between the ECM and the millimeter wave radar sensor assembly is detected for approximately 1 second or more.

Condition 2: 
  • While the vehicle speed is 36 km/h (22 mph) or more and the dynamic radar cruise control system is operating, the ECM continuously receives a communication cut-off signal from the skid control ECU (brake actuator assembly)*1 or skid control ECU (master cylinder solenoid)*2 for approximately 1 second or more.
 Condition 1: 
  • CAN communication system
  • ECM
  • Millimeter wave radar sensor assembly

Condition 2: 
  • CAN communication system
  • ECM
  • Skid control ECU (brake actuator assembly)*1
  • Skid control ECU (master cylinder solenoid)*2
U0104 Lost Communication with Cruise Control Module While the vehicle speed is 36 km/h (22 mph) or more and the dynamic radar cruise control system is operating, a communication error between the ECM and the millimeter wave radar sensor assembly is detected for approximately 1 second or more.
  • CAN communication system
  • ECM
  • Millimeter wave radar sensor assembly
U0122 Lost Communication with Vehicle Dynamics Control Module When the ignition switch is ON and the dynamic radar cruise control system is operating, a communication error between the skid control ECU (brake actuator assembly)*1 or skid control ECU (master cylinder solenoid)*2 and the ECM is detected for approximately 2.6 seconds or more.
  • CAN communication system
  • ECM
  • Skid control ECU (brake actuator assembly)*1
  • Skid control ECU (master cylinder solenoid)*2
U0125 Lost Communication with Yaw Rate Sensor Module While the vehicle speed is 36 km/h (22 mph) or more and the dynamic radar cruise control system is operating, a communication error between the yaw rate sensor and the millimeter wave radar sensor assembly is detected for approximately 1 second or more.
  • CAN communication system
  • Yaw rate sensor (airbag sensor assembly)
  • Millimeter wave radar sensor assembly
U0126 Lost Communication with Steering Angle Sensor Module While the vehicle speed is 36 km/h (22 mph) or more and the dynamic radar cruise control system is operating, a communication error between the steering sensor and the millimeter wave radar sensor assembly is detected for approximately 1 second or more.
  • CAN communication system
  • Steering sensor
  • Millimeter wave radar sensor assembly
U0129 Lost Communication with Brake System Control Module While the vehicle speed is 36 km/h (22 mph) or more and the dynamic radar cruise control system is operating, a communication error between the skid control ECU (brake actuator assembly)*1 or skid control ECU (master cylinder solenoid)*2 and the millimeter wave radar sensor assembly is detected for approximately 2.5 seconds or more.
  • CAN communication system
  • Skid Control ECU (Brake Actuator Assembly)*1
  • Skid Control ECU (Master Cylinder Solenoid)*2
  • Millimeter wave radar sensor assembly
  1. *1: for Vacuum Brake Booster
  2. *2: for Hydraulic Brake Booster
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