PRE-COLLISION SYSTEM, Diagnostic DTC:C1A4B

DTC Code DTC Name
C1A4B Stop Light Relay Circuit

DESCRIPTION

The skid control ECU (brake actuator assembly) sends a stop light operation request signal to the stop light relay (semiconductor power integration ECU). If the skid control ECU (brake actuator assembly) detects a malfunction in the stop light relay (semiconductor power integration ECU) circuit, the driving support ECU assembly stores DTC C1A4B.

DTC No. Detection Item DTC Detection Condition Trouble Area
C1A4B Stop Light Relay Circuit

Both of the following conditions are met:


  1. All of the following conditions are met:


    • 3 seconds have elapsed since the engine switch was turned to on (IG).

    • The battery voltage is 10 V or more for 3 seconds or more.

  2. All of the following conditions are met for 1 second or more:


    • Communication between the driving support ECU assembly and skid control ECU (brake actuator assembly) is normal.

    • The driving support ECU assembly receives a stop light relay circuit malfunction signal from the skid control ECU (brake actuator assembly)

Tech Tips

The skid control ECU (brake actuator assembly) will detect a stop light relay circuit malfunction if any of the following conditions are met:


  • When the voltage at the IG1 terminal is between 11 V and 14 V and the stop light illumination output (STPO) signal is on, a signal has not been input to the STP2 terminal continuously for 0.3 seconds or more.

  • When the voltage at the IG1 terminal is between 11 V and 14 V and the stop light illumination output (STPO) signal is off, the input signals at the STP terminal and STP2 terminal differ continuously for 0.3 seconds or more.

  • Skid control ECU (Brake actuator assembly)

  • Stop light relay (Semiconductor power integration ECU)

  • Rear combination light assembly LH

  • Rear combination light assembly RH

  • Rear light assembly LH

  • Rear light assembly RH

  • Center stop light assembly

  • Harness or connector

WIRING DIAGRAM

B0075U9E02

CAUTION / NOTICE / HINT

Note

Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE


  1. INSPECT TERMINAL VOLTAGE (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) CONNECTOR)


    1. Turn the engine switch off.

    2. B0076QTC78
      *a

      Front view of wire harness connector

      (to Skid control ECU (brake actuator assembly))

      Disconnect the A94 skid control ECU (brake actuator assembly) connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A94-35 (STP) - Body ground Brake pedal depressed 11 to 14 V
      Brake pedal released Below 1.5 V
      A94-26 (STPO) - Body ground Always 11 to 14 V
      A94-5 (STP2) - Body ground Brake pedal depressed 11 to 14 V
      Brake pedal released Below 1.5 V

    4. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Result Proceed to
      The voltage is as specified for every terminal. A
      Only the voltage at terminal STP is not as specified. B
      Only the voltage at terminal STPO is not as specified. C
      Only the voltage at terminal STP2 is not as specified. D
      The voltage at both terminal STPO and terminal STP2 are not as specified. E

    B

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    C

    CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU)) Click here

    D

    INSPECT TERMINAL VOLTAGE (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) CONNECTOR) Click here

    E

    CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU)) Click here

    A

  2. PERFORM ACTIVE TEST USING GTS (STOP LIGHT RELAY)


    1. Turn the engine switch off.

    2. According to the display on the GTS, perform the Active Test Stop Light Relay.

      Click here


      Chassis > ABS/VSC/TRC > Active Test
      Tester Display Measurement Item Control Range Diagnostic Note
      Stop Light Relay Stop Light Relay ON / OFF

      Stop lights come on

      Vehicle condition: Vehicle stopped

      Chassis > ABS/VSC/TRC > Active Test
      Tester Display
      Stop Light Relay
      OK
      The stop lights turn on and off correctly in response to the operation of the Active Test.
      Result
      Proceed to
      OK
      NG

    NG

    INSPECT STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU) Click here

    OK

  3. CHECK FOR DTCS (PRE-COLLISION SYSTEM)


    1. Clear the DTCs.

      Click here


      Body Electrical > Pre-Collision 2 > Clear DTCs

    2. According to the display on the GTS, perform the Active Test Stop Light Relay.

      Click here


      Chassis > ABS/VSC/TRC > Active Test
      Tester Display Measurement Item Control Range Diagnostic Note
      Stop Light Relay Stop Light Relay ON / OFF

      Stop lights come on

      Vehicle condition: Vehicle stopped

      Chassis > ABS/VSC/TRC > Active Test
      Tester Display
      Stop Light Relay

    3. Check for DTCs.

      Click here


      Body Electrical > Pre-Collision 2 > Trouble Codes
      OK
      DTC C1A4B is not output
      Result
      Proceed to
      OK
      NG

    OK

    USE SIMULATION METHOD TO CHECK Click here

    NG

    REPLACE SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) for LHD: Click here for RHD: Click here

  4. INSPECT STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU)


    1. Turn the engine switch off.

    2. Inspect the stop light relay (semiconductor power integration ECU).

      Click here

      OK
      The stop light relay (semiconductor power integration ECU) is normal.
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) for LHD: Click here for RHD: Click here

    NG

    REPLACE STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU) Click here

  5. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU))


    1. Turn the engine switch off.

    2. Remove the stop light relay (semiconductor power integration ECU).

    3. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A94-26 (STPO) - 2D-3 (ACC) Always Below 1 Ω

    5. Connect the A94 skid control ECU (brake actuator assembly) connector.

    6. Install the stop light relay (semiconductor power integration ECU).

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU) Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  6. INSPECT TERMINAL VOLTAGE (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) CONNECTOR)


    1. Turn the engine switch off.

    2. B0076QTC79
      *a

      Front view of wire harness connector

      (to Skid control ECU (brake actuator assembly))

      Disconnect the A94 skid control ECU (brake actuator assembly) connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A94-5 (STP2) - Body ground Brake pedal released Below 1.5 V

    4. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    NG

    CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU)) Click here

    OK

  7. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - REAR COMBINATION LIGHT ASSEMBLY LH)


    1. Turn the engine switch off.

    2. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

    3. Disconnect the U41 rear combination light assembly LH connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A94-5 (STP2) - Body ground Brake pedal depressed 11 to 14 V

    5. Connect the U41 rear combination light assembly LH connector.

    6. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE REAR COMBINATION LIGHT ASSEMBLY LH Click here

    NG

  8. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - REAR COMBINATION LIGHT ASSEMBLY RH)


    1. Turn the engine switch off.

    2. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

    3. Disconnect the U5 rear combination light assembly RH connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A94-5 (STP2) - Body ground Brake pedal depressed 11 to 14 V

    5. Connect the U5 rear combination light assembly RH connector.

    6. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE REAR COMBINATION LIGHT ASSEMBLY RH Click here

    NG

  9. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - CENTER STOP LIGHT ASSEMBLY)


    1. Turn the engine switch off.

    2. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

    3. Disconnect the U8 center stop light assembly connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A94-5 (STP2) - Body ground Brake pedal depressed 11 to 14 V

    5. Connect the U8 center stop light assembly connector.

    6. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE CENTER STOP LIGHT ASSEMBLY Click here

    NG

  10. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - REAR LIGHT ASSEMBLY LH)


    1. Turn the engine switch off.

    2. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

    3. Disconnect the U42 rear light assembly LH connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A94-5 (STP2) - Body ground Brake pedal depressed 11 to 14 V

    5. Connect the U42 rear light assembly LH connector.

    6. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE REAR LIGHT ASSEMBLY LH Click here

    NG

  11. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - REAR LIGHT ASSEMBLY RH)


    1. Turn the engine switch off.

    2. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

    3. Disconnect the U6 rear light assembly RH connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A94-5 (STP2) - Body ground Brake pedal depressed 11 to 14 V

    5. Connect the U6 rear light assembly RH connector.

    6. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE REAR LIGHT ASSEMBLY RH Click here

    NG

  12. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU))


    1. Turn the engine switch off.

    2. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

    3. Remove the stop light relay (semiconductor power integration ECU).

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      2D-10 (STP) - A94-35 (STP) Always Below 1 Ω
      2F-9 (OUT) - A94-5 (STP2) Always Below 1 Ω
      2F-9 (OUT) or A94-5 (STP2) - Body ground Always 10 kΩ or higher

    5. Install the stop light relay (semiconductor power integration ECU).

    6. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU) Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  13. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU))


    1. Turn the engine switch off.

    2. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

    3. Remove the stop light relay (semiconductor power integration ECU).

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A94-5 (STP2) or 2F-9 (OUT) - Body ground Brake pedal released Below 1.5 V

    5. Install the stop light relay (semiconductor power integration ECU).

    6. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU) Click here

    NG

  14. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - REAR COMBINATION LIGHT ASSEMBLY LH)


    1. Turn the engine switch off.

    2. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

    3. Disconnect the U41 rear combination light assembly LH connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A94-5 (STP2) - Body ground Brake pedal released Below 1.5 V

    5. Connect the U41 rear combination light assembly LH connector.

    6. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE REAR COMBINATION LIGHT ASSEMBLY LH Click here

    NG

  15. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - REAR COMBINATION LIGHT ASSEMBLY RH)


    1. Turn the engine switch off.

    2. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

    3. Disconnect the U5 rear combination light assembly RH connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A94-5 (STP2) - Body ground Brake pedal released Below 1.5 V

    5. Connect the U5 rear combination light assembly RH connector.

    6. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE REAR COMBINATION LIGHT ASSEMBLY RH Click here

    NG

  16. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - CENTER STOP LIGHT ASSEMBLY)


    1. Turn the engine switch off.

    2. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

    3. Disconnect the U8 center stop light assembly connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A94-5 (STP2) - Body ground Brake pedal released Below 1.5 V

    5. Connect the U8 center stop light assembly connector.

    6. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE CENTER STOP LIGHT ASSEMBLY Click here

    NG

  17. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - REAR LIGHT ASSEMBLY LH)


    1. Turn the engine switch off.

    2. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

    3. Disconnect the U42 rear light assembly LH connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A94-5 (STP2) - Body ground Brake pedal released Below 1.5 V

    5. Connect the U42 rear light assembly LH connector.

    6. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE REAR LIGHT ASSEMBLY LH Click here

    NG

  18. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - REAR LIGHT ASSEMBLY RH)


    1. Turn the engine switch off.

    2. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

    3. Disconnect the U6 rear light assembly RH connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A94-5 (STP2) - Body ground Brake pedal released Below 1.5 V

    5. Connect the U6 rear light assembly RH connector.

    6. Connect the A94 skid control ECU (brake actuator assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE REAR LIGHT ASSEMBLY RH Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  19. CHECK WIRE HARNESS AND CONNECTOR (SKID CONTROL ECU (BRAKE ACTUATOR ASSEMBLY) - STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU))


    1. Turn the engine switch off.

    2. Remove the stop light relay (semiconductor power integration ECU).

    3. Disconnect the A94 skid control ECU (brake actuator assembly) connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A94-26 (STPO) or 2D-3 (ACC) - Body ground Always 10 kΩ or higher

    5. Connect the A94 skid control ECU (brake actuator assembly) connector.

    6. Install the stop light relay (semiconductor power integration ECU).

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  20. INSPECT STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU)


    1. Turn the engine switch off.

    2. Inspect the stop light relay (semiconductor power integration ECU).

      Click here

      OK
      The stop light relay (semiconductor power integration ECU) is normal.
      Result
      Proceed to
      OK
      NG

    OK

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    NG

    REPLACE STOP LIGHT RELAY (SEMICONDUCTOR POWER INTEGRATION ECU) Click here