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Home >> Lexus >> 2019 >> ES 350 Luxury >> Repair and Diagnosis >> External Pages >> Different car >> Section 108 (Electronically Controlled Brake System (Hybrid) - Diagnostic Codes (2 Of 5)) >> ELECTRONICALLY CONTROLLED BRAKE SYSTEM (for HV Model) >> DTC C1380: Stop Light Control Relay Malfunction [07/2019 - 08/2020] >> Procedure

DTC C1380: Stop Light Control Relay Malfunction [07/2019 - 08/2020]: Procedure

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2024 Lexus ES 300h, 2023 Lexus ES 300h, 2022 Lexus ES 300h, 2021 Lexus ES 300h, and 2020 Lexus ES 300h. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK HARNESS AND CONNECTOR (STP, STPO AND STP2 TERMINAL) 
    1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
      GTY821280Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      OK

      The connector is securely connected.

    2. Disconnect the A45 skid control ECU (brake booster with master cylinder assembly) connector.
    3. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A45-12 (STP) - Body ground Stop light switch assembly on (Brake pedal depressed) 11 to 14 V
      A45-12 (STP) - Body ground Stop light switch assembly off (Brake pedal released) 1.5 V or less
      A45-22 (STPO) - Body ground Always 11 to 14 V
      A45-37 (STP2) - Body ground Stop light switch assembly on (Brake pedal depressed) 11 to 14 V
      A45-37 (STP2) - Body ground Stop light switch assembly off (Brake pedal released) 1.5 V or less

      Result

      Result Proceed to
      All terminal voltages are normal. A
      Only STP2 terminal voltage abnormal. B
      Only STPO terminal voltage abnormal. C
      Only STP terminal voltage abnormal. D
      STPO terminal and STP terminal voltage abnormal. E

    Result: 

    B 

    See step  5

    Result: 

    C 

    See step  9

    Result: 

    D 

    See step  10

    Result: 

    E 

    See step  17

    Result: 

    A 

    See step  2

  2. PERFORM ACTIVE TEST USING TECHSTREAM (STOP LIGHT RELAY) 
    1. Reconnect the A45 skid control ECU (brake booster with master cylinder assembly) connector.
    2. Select the Active Test on the Techstream.

      Refer to DATA LIST / ACTIVE TEST [06/2018 - ]

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display Measurement Item Control Range Diagnostic Note
      Stop Light Relay Stop light control relay (Stop light switch assembly) Relay ON/OFF -

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display
      Stop Light Relay
    3. According to the display on the Techstream, perform the Active Test and check the operation of the stop lights.

      OK

      Stop lights turn on/off in accordance with the Active Test.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  4

    Result: 

    OK 

    See step  3

  3. RECONFIRM DTC 
    1. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [06/2018 - ]

      Chassis > ABS/VSC/TRAC > Clear DTCs 

    2. Select the Active Test on the Techstream.

      Refer to DATA LIST / ACTIVE TEST [06/2018 - ]

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display Measurement Item Control Range Diagnostic Note
      Stop Light Relay Stop light control relay (Stop light switch assembly) Relay ON/OFF -

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display
      Stop Light Relay
    3. According to the display on the Techstream, perform the Active Test.
    4. Check if the same DTC is output.

      Refer to DTC CHECK / CLEAR [06/2018 - ]

      Chassis > ABS/VSC/TRAC > Trouble Codes 

      Result

      Result Proceed to
      DTC C1380 is output. A
      DTC C1380 is not output. B

    Result: 

    A 

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY. Refer to  REMOVAL [06/2018 - 08/2021] 

    Result: 

    B 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [06/2018 - ] 

  4. INSPECT BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY 
    1. Select the Active Test on the Techstream.

      Refer to DATA LIST / ACTIVE TEST [06/2018 - ]

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display Measurement Item Control Range Diagnostic Note
      Stop Light Relay Stop light control relay (Stop light switch assembly) Relay ON/OFF -

      Chassis > ABS/VSC/TRAC > Active Test 

      Tester Display
      Stop Light Relay
    2. Measure the voltage according to the value(s) in the table below.
      GTY783883Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Stop Light Switch Assembly)

      Standard Voltage

      Tester Connection Condition Specified Condition
      A43-4 (ACC) - Body ground Active Test is on 1.5 V or less

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  REMOVAL [06/2018 - ] 

    Result: 

    NG 

    REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY. Refer to  REMOVAL [06/2018 - 08/2021] 

  5. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - HYBRID VEHICLE CONTROL ECU) 
    1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
      GTY821278Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      OK

      The connector is securely connected.

    2. Disconnect the A32 hybrid vehicle control ECU connector.
    3. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A45-37 (STP2) - Body ground Stop light switch assembly on (Brake pedal depressed) 11 to 14 V
      A45-37 (STP2) - Body ground Stop light switch assembly off (Brake pedal released) 1.5 V or less

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE HYBRID VEHICLE CONTROL ECU. Refer to  REMOVAL [06/2018 - 08/2021] 

    Result: 

    NG 

    See step  6

  6. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - SMART KEY ECU ASSEMBLY) 
    1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
      GTY821278Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      OK

      The connector is securely connected.

    2. Disconnect the N9 certification ECU (smart key ECU assembly) connector.
    3. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A45-37 (STP2) - Body ground Stop light switch assembly on (Brake pedal depressed) 11 to 14 V
      A45-37 (STP2) - Body ground Stop light switch assembly off (Brake pedal released) 1.5 V or less

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE SMART KEY ECU ASSEMBLY. Refer to  REMOVAL [06/2018 - 08/2021] 

    Result: 

    NG 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - STOP LIGHT SWITCH ASSEMBLY) 
    1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
      GTY821278Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      OK

      The connector is securely connected.

    2. Disconnect the A43 stop light switch assembly connector.
    3. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A45-37 (STP2) - Body ground Always 1.5 V or less

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  8

  8. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - STOP LIGHT SWITCH ASSEMBLY) 
    1. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A45-37 (STP2) - A43-3 (L) Always Below 1 Ω
      A45-37 (STP2) or A43-3 (L) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  REMOVAL [06/2018 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  9. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - STOP LIGHT SWITCH ASSEMBLY) 
    1. Make sure that there is no looseness at the locking part and the connecting part of the connector.

      OK

      The connector is securely connected.

    2. Disconnect the A43 stop light switch assembly connector.
    3. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

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

      Standard Resistance

      Tester Connection Condition Specified Condition
      A45-22 (STPO) - A43-4 (ACC) Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  REMOVAL [06/2018 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  10. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - REAR COMBINATION LIGHT ASSEMBLY LH) 
    1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
      GTY778871Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      OK

      The connector is securely connected.

    2. Disconnect the R9 rear combination light assembly LH connector.
    3. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A45-12 (STP) - Body ground Stop light switch assembly on (Brake pedal depressed) 11 to 14 V
      A45-12 (STP) - Body ground Stop light switch assembly off (Brake pedal released) 1.5 V or less

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE REAR COMBINATION LIGHT ASSEMBLY LH. Refer to  REMOVAL [06/2018 - 08/2021] 

    Result: 

    NG 

    See step  11

  11. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - REAR COMBINATION LIGHT ASSEMBLY RH) 
    1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
      GTY778871Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      OK

      The connector is securely connected.

    2. Disconnect the R8 rear combination light assembly RH connector.
    3. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A45-12 (STP) - Body ground Stop light switch assembly on (Brake pedal depressed) 11 to 14 V
      A45-12 (STP) - Body ground Stop light switch assembly off (Brake pedal released) 1.5 V or less

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE REAR COMBINATION LIGHT ASSEMBLY RH. Refer to  REMOVAL [06/2018 - 08/2021] 

    Result: 

    NG 

    See step  12

  12. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - REAR LIGHT ASSEMBLY LH) 
    1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
      GTY778871Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      OK

      The connector is securely connected.

    2. Disconnect the R11 rear light assembly LH connector.
    3. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A45-12 (STP) - Body ground Stop light switch assembly on (Brake pedal depressed) 11 to 14 V
      A45-12 (STP) - Body ground Stop light switch assembly off (Brake pedal released) 1.5 V or less

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE REAR LIGHT ASSEMBLY LH. Refer to  REMOVAL [06/2018 - ] 

    Result: 

    NG 

    See step  13

  13. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - REAR LIGHT ASSEMBLY RH) 
    1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
      GTY778871Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      OK

      The connector is securely connected.

    2. Disconnect the R10 rear light assembly RH connector.
    3. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A45-12 (STP) - Body ground Stop light switch assembly on (Brake pedal depressed) 11 to 14 V
      A45-12 (STP) - Body ground Stop light switch assembly off (Brake pedal released) 1.5 V or less

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE REAR LIGHT ASSEMBLY RH. Refer to  REMOVAL [06/2018 - ] 

    Result: 

    NG 

    See step  14

  14. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - CENTER STOP LIGHT SET) 
    1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
      GTY778871Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      OK

      The connector is securely connected.

    2. Disconnect the N52 center stop light set connector.
    3. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A45-12 (STP) - Body ground Stop light switch assembly on (Brake pedal depressed) 11 to 14 V
      A45-12 (STP) - Body ground Stop light switch assembly off (Brake pedal released) 1.5 V or less

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE CENTER STOP LIGHT SET. Refer to  REMOVAL [06/2018 - ] 

    Result: 

    NG 

    See step  15

  15. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - STOP LIGHT SWITCH ASSEMBLY) 
    1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
      GTY778871Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

      OK

      The connector is securely connected.

    2. Disconnect the A43 stop light switch assembly connector.
    3. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A45-12 (STP) - Body ground Always 1.5 V or less

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  16

  16. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - STOP LIGHT SWITCH ASSEMBLY) 
    1. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A43-1 (OUT) - A45-12 (STP) Always Below 1 Ω
      A43-1 (OUT) or A45-12 (STP) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  REMOVAL [06/2018 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  17. CHECK STOP LIGHT SWITCH ASSEMBLY POWER SOURCE CIRCUIT 
    1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
      GTY807262Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Stop Light Switch Assembly)

      OK

      The connector is securely connected.

    2. Disconnect the A43 stop light switch assembly connector.
    3. Check both the connector case and the terminals for deformation and corrosion.

      OK

      No deformation or corrosion.

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

      Standard Voltage

      Tester Connection Condition Specified Condition
      A43-7 (B) - Body ground Always 11 to 14 V
    5. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A43-2 (GND) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  18

  18. CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - STOP LIGHT SWITCH ASSEMBLY) 
    1. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A45-22 (STPO) or A43-4 (ACC) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  REMOVAL [06/2018 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

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