Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Lost Communication with ECM / PCM "A" (U0100,U0126,U0129)

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Drivetrain / Mf1a (transfer / 4wd / Awd) / Dynamic Torque Control Awd System / Lost Communication with ECM / PCM "A" (U0100,U0126,U0129)

DESCRIPTION

The 4WD ECU assembly receives signals from the ECM, skid control ECU (brake actuator assembly) and steering sensor via CAN communication.

When DTCs indicating a CAN communication system malfunction are output, repair the CAN communication system before repairing each corresponding sensor.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

U0100

Lost Communication with ECM / PCM "A"
  • When both of the following continue for 2 seconds or more:
    • The IG1 terminal voltage is 10 V or more.
    • At a vehicle speed of 60 km/h (38 mph) or more, communication with the ECM cannot be performed.
  • CAN communication system
  • 4WD ECU assembly
  • ECM

U0126

Lost Communication with Steering Angle Sensor Module
  • When both of the following continue for 1 second or more:
    • The IG1 terminal voltage is 10 V or more.
    • Communication with the steering sensor cannot be performed.
  • When all of the following occur 10 times consecutively:
    • The IG1 terminal voltage is 10 V or more.
    • A communication malfunction with the steering sensor occurs once within 5 seconds, 10 times or more within 60 seconds.
  • CAN communication system
  • 4WD ECU assembly
  • Steering sensor

U0129

Lost Communication with Brake System Control Module
  • When the following continues for 3 seconds or more:
    • The IG1 terminal voltage is 10 V or more.
    • Communication with the skid control ECU (brake actuator assembly) cannot be performed.
  • CAN communication system
  • 4WD ECU assembly
  • Skid control ECU (Brake actuator assembly)

PROCEDURE

1.

CHECK FOR DTC

(a) Check for DTCs.

Click here

Chassis > Four Wheel Drive > Trouble Codes

(b) Write down any output DTCs.

NEXT

GO TO CAN COMMUNICATION SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING)

    Control Module Communication Bus Off (U0073)
    DESCRIPTION The 4WD ECU assembly stores this DTC when a communication malfunction is detected. DTC No. Detection Item DTC Detection Condition Trouble Area U0073 Control Module Communica ...

    AWD Warning Light Remains ON
    DESCRIPTION The 4WD ECU assembly is connected to the combination meter assembly via CAN communication. If the 4WD ECU assembly stores any DTCs which are related to the dynamic torque control AWD syste ...

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