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Home >> Lexus >> 2017 >> RX 450h Base >> Repair and Diagnosis (Single Page) >> Restraints >> Restraints Control Systems >> Pre-Collision System (Diagnostic Codes & Circuit Tests) >> Pre-Collision System >> DTC U1104: Lost Communication with Driving Support ECU [08/2018 - 08/2019] >> Procedure

DTC U1104: Lost Communication with Driving Support ECU [08/2018 - 08/2019]: Procedure

  1. CHECK FOR DTCs (PRE-COLLISION SYSTEM) 
    1. Check for DTCs.

      Refer to DTC CHECK / CLEAR [10/2015 - 08/2019]

      Body Electrical > Pre-Collision 2 > Trouble Codes 

      Result

      Result Proceed to
      DTC U1104 and other DTCs are output A
      Only DTC U1104 is output B

    Result: 

    A 

    GO TO DIAGNOSTIC TROUBLE CODE CHART. Refer to  DIAGNOSTIC TROUBLE CODE CHART [08/2018 - 08/2019] 

    Result: 

    B 

    See step  2

  2. CHECK FOR DTCs (FORWARD RECOGNITION CAMERA SYSTEM) 
    1. Check for DTCs.

      Refer to DTC CHECK / CLEAR [10/2015 - 08/2019]

      Chassis > Front Recognition Camera > Trouble Codes 

      Result

      Result Proceed to
      Forward recognition camera system DTCs are not output A
      Forward recognition camera system DTCs are output B

    Result: 

    B 

    GO TO FORWARD RECOGNITION CAMERA SYSTEM. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [10/2015 - 08/2019] 

    Result: 

    A 

    See step  3

  3. CHECK FOR DTCs (ELECTRONICALLY CONTROLLED BRAKE SYSTEM) 
    1. Check for DTCs.

      Refer to DTC CHECK / CLEAR [08/2018 - 08/2019]

      Chassis > ABS/VSC/TRAC > Trouble Codes 

      Result

      Result Proceed to
      Electronically controlled brake system DTC are not output A
      Electronically controlled brake system DTC are output B

    Result: 

    B 

    GO TO ELECTRONICALLY CONTROLLED BRAKE SYSTEM. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [08/2018 - 08/2019] 

    Result: 

    A 

    See step  4

  4. TEST MODE INSPECTION (ELECTRONICALLY CONTROLLED BRAKE SYSTEM) 

    HINT: 

    When entering test mode, the skid control ECU assembly communicates with the driving support ECU assembly to judge whether the vehicle is equipped with the pre-collision system. Therefore, do not exit test mode within 5 seconds of entering test mode.

    1. Procedure to Enter Test Mode (Signal Check)
      1. Turn the power switch off.
      2. Check that the steering wheel is centered.
      3. Check that the shift lever is in P.
      4. Check that the parking brake is released.
      5. Connect the Techstream to the DLC3.
      6. Turn the power switch on (IG).
      7. Turn the Techstream on.
      8. Switch the skid control ECU assembly to Test Mode (signal check) using the Techstream. Enter the following menus: Chassis / ABS/VSC/TRAC / Utility / Signal Check.

        Chassis > ABS/VSC/TRAC > Utility 

        Tester Display
        Signal Check

        HINT: 

        Do not exit test mode within 5 seconds of entering test mode. If test mode is exited within 5 seconds of entering test mode, DTC U1104 may be stored. If DTC U1104 is output after exiting test mode, enter test mode again, wait at least 5 seconds, then recheck for DTCs.

      9. Check that the ABS warning, brake warning / yellow (minor malfunction) and slip indicator lights come on for several seconds and then blink in the Test Mode pattern.

        HINT: 

        If the ABS warning, brake warning / yellow (minor malfunction) and slip indicator lights do not blink, inspect the ABS warning, brake warning / yellow (minor malfunction) and slip indicator light circuits.

    2. End of Test Mode (Signal Check)
      1. Turn the power switch off and disconnect the Techstream.

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  5

  5. CHECK FOR DTCs (PRE-COLLISION SYSTEM) 
    1. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [10/2015 - 08/2019]

      Body Electrical > Pre-Collision 2 > Clear DTCs 

    2. Perform the following procedure.

      HINT: 

      If the following procedure is not performed, the previously output DTC cannot be detected.

      1. Turn the power switch on (IG) and wait 1.5 seconds or more.
    3. Check for DTCs.

      Refer to DTC CHECK / CLEAR [10/2015 - 08/2019]

      Body Electrical > Pre-Collision 2 > Trouble Codes 

      Result

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

    Result: 

    A 

    END 

    Result: 

    B 

    See step  6

  6. REPLACE MILLIMETER WAVE RADAR SENSOR ASSEMBLY 
    1. Replace the millimeter wave radar sensor assembly.

      Refer to REMOVAL [10/2015 - 08/2019]

    2. Adjust the millimeter wave radar sensor assembly.

      Refer to ADJUSTMENT [03/2018 - 08/2019]

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  7

  7. CHECK FOR DTCs (PRE-COLLISION SYSTEM) 
    1. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [10/2015 - 08/2019]

      Body Electrical > Pre-Collision 2 > Clear DTCs 

    2. Perform the following procedure.

      HINT: 

      If the following procedure is not performed, the previously output DTC cannot be detected.

      1. Turn the power switch on (IG) and wait 1.5 seconds or more.
    3. Check for DTCs.

      Refer to DTC CHECK / CLEAR [10/2015 - 08/2019]

      Body Electrical > Pre-Collision 2 > Trouble Codes 

      Result

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

    Result: 

    A 

    END (MILLIMETER WAVE RADAR SENSOR ASSEMBLY WAS DEFECTIVE) 

    Result: 

    B 

    See step  8

  8. REPLACE DRIVING SUPPORT ECU ASSEMBLY 
    1. Replace the driving support ECU assembly.

      Refer to REMOVAL [08/2016 - 08/2019]

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  9

  9. CHECK FOR DTCs (PRE-COLLISION SYSTEM) 
    1. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [10/2015 - 08/2019]

      Body Electrical > Pre-Collision 2 > Clear DTCs 

    2. Perform the following procedure.

      HINT: 

      If the following procedure is not performed, the previously output DTC cannot be detected.

      1. Turn the power switch on (IG) and wait 1.5 seconds or more.
    3. Check for DTCs.

      Refer to DTC CHECK / CLEAR [10/2015 - 08/2019]

      Body Electrical > Pre-Collision 2 > Trouble Codes 

      Result

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

    Result: 

    A 

    END (DRIVING SUPPORT ECU ASSEMBLY WAS DEFECTIVE) 

    Result: 

    B 

    See step  10

  10. REPLACE FORWARD RECOGNITION CAMERA 
    1. Replace the forward recognition camera.

      Refer to REMOVAL [10/2015 - 08/2019]

    2. Perform Forward Recognition Camera Learning.

      Refer to ADJUSTMENT [10/2015 - 08/2019]

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  11

  11. CHECK FOR DTCs (PRE-COLLISION SYSTEM) 
    1. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [10/2015 - 08/2019]

      Body Electrical > Pre-Collision 2 > Clear DTCs 

    2. Perform the following procedure.

      HINT: 

      If the following procedure is not performed, the previously output DTC cannot be detected.

      1. Turn the power switch on (IG) and wait 1.5 seconds or more.
    3. Check for DTCs.

      Refer to DTC CHECK / CLEAR [10/2015 - 08/2019]

      Body Electrical > Pre-Collision 2 > Trouble Codes 

      Result

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

    Result: 

    A 

    END (FORWARD RECOGNITION CAMERA WAS DEFECTIVE) 

    Result: 

    B 

    See step  12

  12. REPLACE SKID CONTROL ECU ASSEMBLY 
    1. Replace the skid control ECU assembly.

      Refer to REMOVAL [03/2018 - 08/2019]

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    END (SKID CONTROL ECU ASSEMBLY WAS DEFECTIVE) 

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