SFI SYSTEM, Diagnostic DTC:U0129, U1103

DTC Code DTC Name
U0129 Lost Communication with Brake System Control Module
U1103 Lost Communication with Stop and Start Control Module

DESCRIPTION

The Controller Area Network (CAN) is a serial data communication system for real time applications. This is a vehicle multiplex communication system which has a high communication speed (500 kbps) and a high level of ability to detect malfunctions. By pairing the CANH and CANL bus wires, the communication on the CAN is performed using the voltage differential between the wires.

DTC No. Detection Item DTC Detection Condition Trouble Area MIL Memory
U0129 Lost Communication with Brake System Control Module

  • All of the following conditions are met for 2.22 seconds or more (1 trip detection logic):


    1. Ignition switch ON

    2. Battery voltage is 10.5 V or more

    3. No communication between ECM and skid control ECU

  • Wire harness (CANL and CANH circuit)

  • ECM

  • Skid control ECU (Brake actuator assembly)

  • CAN communication system

 Comes on (for CVT) / Does not come on (for Manual Transaxle) DTC stored (for CVT) / - (for Manual Transaxle)
U1103 Lost Communication with Stop and Start Control Module

  • Both of the following conditions are met for 1.25 seconds (1 trip detection logic):


    1. Ignition switch ON

    2. No communication between ECM and stop and start ECU

  • Wire harness (CANL and CANH circuits)

  • ECM

  • Engine stop and start ECU

 Does not come on DTC stored (w/ Stop and Start System) / - (w/o Stop and Start System)

CAUTION / NOTICE / HINT

Tech Tips

Read freeze frame data using the GTS. Freeze frame data records the engine conditions when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE


  1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC U0129 OR U1103)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

    5. Read DTCs

      Result
      Result Proceed to
      DTC U0129 or U1103 and other DTCs are not output A
      DTC U0129 or U1103 is output *1 B
      DTC U0129 or U1103 is output *2 C

      • *1: w/ Toyota Safety Sense

      • *2: w/o Toyota Safety Sense

      Tech Tips

      If any DTCs other than U0129 or U1103 are output, troubleshoot those DTCs first.


    A

    CHECK FOR INTERMITTENT PROBLEMS Click here

    B

    GO TO CAN COMMUNICATION SYSTEM Click here

    C

    GO TO CAN COMMUNICATION SYSTEM Click here