PRE-CRASH SAFETY SYSTEM, Diagnostic DTC:U1104

DTC Code DTC Name
U1104 Lost Communication with Driving Support ECU

DESCRIPTION

The driving support ECU sends vehicle speed and vehicle condition information to the millimeter wave radar sensor. The millimeter wave radar sensor then sends information on the presence, distance, and relative speed of objects ahead to the driving support ECU. The driving support ECU sends this information to the ECM and performs cruise control.

DTC No. DTC Detection Condition Trouble Area
U1104 When the engine switch is on (IG), a communication error between the driving support ECU and the millimeter wave radar sensor is detected for approx. 1 second.

  • Communication circuit

  • Millimeter wave radar sensor

  • Driving support ECU

WIRING DIAGRAM

A019OHXE10

INSPECTION PROCEDURE

Note


  • When replacing the millimeter wave radar sensor with a new one, make sure to perform Adjust Millimeter Wave Radar Sensor Assembly Click here.

  • Confirm that the connector is securely connected, as a partially connected connector is suspected for the cause of this DTC.

PROCEDURE


  1. CHECK HARNESS AND CONNECTOR (DRIVING SUPPORT ECU - MILLIMETER WAVE RADAR SENSOR)


    1. A019NJNE04
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Millimeter Wave Radar Sensor)
      *2

      Front view of wire harness connector

      (to Driving Support ECU)

      Disconnect the driving support ECU and millimeter wave radar sensor connectors.

    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      C1-38 (LRRD) - B1-4 (LRRD) Always Below 1 Ω
      B1-4 (LRRD) - Body ground Always 10 kΩ or higher
      C1-38 (LRRD) - Body ground Always 10 kΩ or higher

    3. Reconnect the driving support ECU and millimeter wave radar sensor connectors.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (DRIVING SUPPORT ECU - MILLIMETER WAVE RADAR SENSOR)

    OK

  2. CHECK MILLIMETER WAVE RADAR SENSOR (IGB VOLTAGE)


    1. A019LQPE01
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Millimeter Wave Radar Sensor)

      Disconnect the millimeter wave radar sensor connector.

    2. Turn the engine switch on (IG).

    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      B1-5 (IGB) - Body ground Engine switch on (IG) 11 to 14 V

    4. Reconnect the millimeter wave radar sensor connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (IGB CIRCUIT)

    OK

  3. CHECK MILLIMETER WAVE RADAR SENSOR (SGND CIRCUIT)


    1. A019LQPE03
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Millimeter Wave Radar Sensor)

      Disconnect the millimeter wave radar sensor connector.

    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      B1-2 (SGND) - Body ground Always Below 1 Ω

    3. Reconnect the millimeter wave radar sensor connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (SGND CIRCUIT)

    OK

  4. CHECK MILLIMETER WAVE RADAR SENSOR (LRRD OUTPUT VOLTAGE)


    1. A019MFKE05
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Driving Support ECU)

      Disconnect the driving support ECU connector.

    2. Turn the engine switch on (IG).

    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      C1-38 (LRRD) - Body ground Engine switch on (IG) 4.5 to 5.5 V

    4. Reconnect the driving support ECU connector.


    NG

    REPLACE MILLIMETER WAVE RADAR SENSOR Click here

    OK

  5. REPLACE DRIVING SUPPORT ECU


    1. Replace the driving support ECU Click here.


    NEXT

  6. CHECK DTC OUTPUT


    1. Clear the DTCs Click here.

    2. Turn the cruise control main switch on.

    3. Drive the vehicle at the required speed (45 km/h (27 mph) or higher).

    4. Check if the same DTC is output Click here.

      Result
      Result Proceed to
      DTC U1104 is not output A
      DTC U1104 is output B

    B

    REPLACE MILLIMETER WAVE RADAR SENSOR Click here

    A

    END