PRE-CRASH SAFETY SYSTEM, Diagnostic DTC:C1A4B

DTC Code DTC Name
C1A4B Stop Light Relay Circuit

DESCRIPTION

The skid control ECU (brake booster with master cylinder assembly) sends a stop light operation request signal to the stop light relay (stop light switch assembly). If the skid control ECU (brake booster with master cylinder assembly) detects a malfunction in the stop light relay circuit, the driving support ECU assembly will store DTC C1A4B.

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

Diagnosis condition:


  • Power switch on (IG) and auxiliary battery voltage between 11 and 14 V

Malfunction condition:

Either of the following conditions is met:


  • When the stop light illumination output (STPO) signal is on, a signal has not been input to the STP terminal for 0.3 seconds or more continuously.

  • When the stop light illumination output (STPO) signal is off, signals input to the STP terminal and STP2 terminal of the skid control ECU (brake booster with master cylinder assembly) differ for 0.3 seconds or more continuously.

  • Lighting system

  • Skid control ECU (Brake booster with master cylinder assembly)

  • Stop light relay (Stop light switch assembly)

  • Wire harness or connector

WIRING DIAGRAM

B004QLRE07

CAUTION / NOTICE / HINT

Note


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

  • When this DTC is output, a malfunction in the lighting system is suspected. Check if the lighting system is functioning normally.

    Click here

  • The pre-crash safety system uses the CAN communication system. First, confirm that there are no malfunction in the CAN communication system. Refer to How to Proceed with Troubleshooting.

    Click here

PROCEDURE


  1. INSPECT HYBRID SYSTEM START


    1. Depress the brake pedal, push the power switch and check that the power switch turns on (READY).

      OK
      The power switch turns on (READY).
      Result
      Proceed to
      OK
      NG

    NG

    GO TO HYBRID CONTROL SYSTEM Click here

    OK

  2. CHECK STOP LIGHT OPERATION


    1. Check that the stop lights come on when the brake pedal is depressed and go off when the brake pedal is released.

      OK
      The stop lights illuminate when the brake pedal is depressed. The stop lights turn off when the brake pedal is released.
      Result
      Proceed to
      OK
      NG

    NG

    GO TO LIGHTING SYSTEM Click here

    OK

  3. INSPECT STOP LIGHT RELAY (STOP LIGHT SWITCH ASSEMBLY)


    1. Turn the power switch off.

    2. Inspect the stop light relay (stop light switch assembly).

      Click here

      Result
      Result Proceed to
      The stop light relay (stop light switch assembly) is normal A
      The stop light relay (stop light switch assembly) is abnormal B

    B

    REPLACE STOP LIGHT RELAY (STOP LIGHT SWITCH ASSEMBLY) Click here

    A

  4. CHECK FOR DTCs (ELECTRONICALLY CONTROLLED BRAKE SYSTEM)


    1. Check for DTCs.


      Chassis > ABS/VSC/TRC > Trouble Codes
      Result
      Result Proceed to
      DTCs are not output A
      DTCs are output B

    B

    GO TO ELECTRONICALLY CONTROLLED BRAKE SYSTEM Click here

    A

  5. CHECK HARNESS AND CONNECTOR (STPO TERMINAL VOLTAGE)


    1. Turn the power switch off.

    2. Disconnect the A41 skid control ECU (brake booster with master cylinder assembly) connector.

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

      Standard Voltage
      Tester Connection Condition Specified Condition
      A41-22 (STPO) - Body ground Always 11 to 14 V

    4. Connect the A41 skid control ECU (brake booster with master cylinder assembly) connector.

      Result
      Proceed to
      OK
      NG

    NG

    CHECK HARNESS AND CONNECTOR (STOP LIGHT RELAY - SKID CONTROL ECU) Click here

    OK

  6. PERFORM ACTIVE TEST USING TECHSTREAM (STOP LIGHT RELAY)


    1. According to the display on the Techstream, perform the Active Test Stop Light Relay.


      Chassis > ABS/VSC/TRC > Active Test
      Tester Display Measurement Item Control Range Diagnostic Note
      Stop Light Relay Stop light control relay (Stop light switch assembly) ON / OFF Test possible at vehicle speed of 0 km/h (0 mph)

      Chassis > ABS/VSC/TRC > Active Test
      Active Test Display
      Stop Light Relay
      Data List Display
      Stop Light Relay Output

    2. According to the display on the Techstream, perform the Data List Stop Light Relay Output.


      Chassis > ABS/VSC/TRC > Data List
      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      Stop Light Relay Output

      Stop light control relay (Stop light switch assembly)

      (STPO terminal output)

      		 ON or OFF

      ON: Output

      OFF: Not output

      		 -

    3. Check that the Data List item Stop Light Relay Output changes between ON and OFF and the stop lights turn on and off according to the operation of the Active Test.

      Result
      Result Proceed to
      The Data List item Stop Light Relay Output does not change between ON and OFF and the stop lights do not turn ON and OFF according to the operation of the Active Test. A
      The Data List item Stop Light Relay Output changes between ON and OFF but the stop lights do not turn ON and OFF according to the operation of the Active Test. B

    B

    CHECK HARNESS AND CONNECTOR (STOP LIGHT RELAY - SKID CONTROL ECU) Click here

    A

  7. INSPECT SKID CONTROL ECU (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY)


    1. According to the display on the Techstream, perform the Active Test Stop Light Relay.


      Chassis > ABS/VSC/TRC > Active Test
      Tester Display Measurement Item Control Range Diagnostic Note
      Stop Light Relay Stop light control relay (Stop light switch assembly) ON / OFF Test possible at vehicle speed of 0 km/h (0 mph)

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

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

      Tech Tips

      Do not disconnect the stop light relay (stop light switch assembly) connector.

      Standard Voltage
      Tester Connection Condition Specified Condition
      A47-4 (ACC) - Body ground

      Power switch on (IG)

      (Active test OFF)

      		 11 to 14 V
      A47-4 (ACC) - Body ground

      Power switch on (IG)

      (Active test ON)

      		 Below 1.5 V
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE STOP LIGHT RELAY (STOP LIGHT SWITCH ASSEMBLY) Click here

    NG

    REPLACE SKID CONTROL ECU (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY) for LHD: Click here for RHD: Click here

  8. CHECK HARNESS AND CONNECTOR (STOP LIGHT RELAY - SKID CONTROL ECU)


    1. Turn the power switch off.

    2. Disconnect the A47 stop light relay (stop light switch assembly) connector.

    3. Disconnect the A41 skid control ECU (brake booster with master cylinder assembly) connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A47-1 (OUT) - A41-12 (STP) Always Below 1 Ω

    5. Connect the A41 skid control ECU (brake booster with master cylinder assembly) connector.

    6. Connect the A47 stop light relay (stop light switch assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE SKID CONTROL ECU (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY) for LHD: Click here for RHD: Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

  9. CHECK HARNESS AND CONNECTOR (STOP LIGHT RELAY - SKID CONTROL ECU)


    1. Turn the power switch off.

    2. Disconnect the A47 stop light relay (stop light switch assembly) connector.

    3. Disconnect the A41 skid control ECU (brake booster with master cylinder assembly) connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A47-4 (ACC) - A41-22 (STPO) Always Below 1 Ω
      A47-4 (ACC) or A41-22 (STPO) - Body ground Always 10 kΩ or higher

    5. Connect the A41 skid control ECU (brake booster with master cylinder assembly) connector.

    6. Connect the A47 stop light relay (stop light switch assembly) connector.

      Result
      Proceed to
      OK
      NG

    OK

    REPLACE STOP LIGHT RELAY (STOP LIGHT SWITCH ASSEMBLY) Click here

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR