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 signal to the stop light switch assembly. When the skid control ECU (brake booster with master cylinder assembly) detects a malfunction in the stop light circuit, the driving support ECU assembly stores DTC C1A4B.

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

Either of the following conditions is met:


  • When the power switch is on (IG), the IG1 terminal voltage is between 11 and 14 V and the stop light illumination output signal (STPO) is output, the signal is not received at terminal STP2 for 0.3 seconds or more.

  • When the power switch is on (IG), the IG1 terminal voltage is between 11 and 14 V and the stop light illumination output signal (STPO) is not output, the signals received at terminals STP and STP2 are different for 0.3 seconds or more.

  • Lighting system

  • Electronically controlled brake system

  • Harness or connector

  • Stop light switch assembly

  • Driving support ECU assembly
Vehicle Condition
Pattern 1 Pattern 2
Diagnosis Condition IG1 terminal voltage is 11 to 14 V ○ ○
Stop Light illumination output(STPO) ON ○ -
Stop Light illumination output(STPO) OFF - ○
Malfunction Status No signal input to STP2 terminal ○ -
Signals input to STP and STP2 terminals do not match - ○
Malfunction Time 0.3 seconds or more 0.3 seconds or more
Number of Trips - -

WIRING DIAGRAM

A01MJ07E06

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

  • When replacing the driving support ECU assembly, always replace it with a new one. If a driving support ECU assembly which was installed to another vehicle is used, the information stored in the driving support ECU assembly will not match the information from the vehicle. As a result, a DTC may be stored.

PROCEDURE


  1. 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
      Condition Illumination Condition
      Brake pedal depressed On
      Brake pedal released Off
      Result
      Proceed to
      OK
      NG

    NG

    GO TO LIGHTING SYSTEM Click here

    OK

  2. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - POWER SOURCE CIRCUIT)


    1. A01MHHIC05
      *a

      Front view of wire harness connector

      (to Stop Light Switch Assembly)

      Disconnect the stop light switch assembly connector.

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

      Standard Voltage
      Tester Connection Switch Condition Specified Condition
      A17-6 (B) - Body ground Power switch on (IG) 11 to 14 V
      A17-7 (B) - Body ground Power switch off 11 to 14 V

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A17-2 (GND) - Body ground Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. INSPECT STOP LIGHT SWITCH ASSEMBLY


    1. Remove the stop light switch assembly.

      Click here

    2. Inspect the stop light switch assembly.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE STOP LIGHT SWITCH ASSEMBLY Click here

    OK

  4. CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - SKID CONTROL ECU (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY))


    1. Disconnect the A17 stop light switch assembly connector.

    2. Disconnect the A63 skid control ECU (brake booster with master cylinder assembly) connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      A17-1 (OUT) - A63-33 (STP) Always Below 1 Ω
      A17-4 (ACC) - A63-3 (STPO) Always Below 1 Ω
      A17-3 (L) - A63-6 (STP2) Always Below 1 Ω
      A17-1 (OUT) or A63-33 (STP) - Body ground Always 10 kΩ or higher
      A17-4 (ACC) or A63-3 (STPO) - Body ground Always 10 kΩ or higher
      A17-3 (L) or A63-6 (STP2) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  5. CHECK FOR DTCs (PRE-CRASH 2)


    1. Turn the power switch off and wait for at least 2 minutes.

    2. Clear the DTCs.

      Click here


      Body Electrical > Pre-Crash 2 > Clear DTCs

    3. Make sure that the DTC detection conditions are met.

      Tech Tips

      If the detection conditions are not met, the system cannot detect the malfunction.


      • Using the GTS, perform the Active Test "Stop Light Relay" with the power switch on (IG).

    4. Check for DTCs.

      Click here


      Body Electrical > Pre-Crash 2 > Trouble Codes
      Result
      Result Proceed to
      DTC C1A4B is not output A
      DTC C1A4B is output B

    B

    USE SIMULATION METHOD TO CHECK Click here

    A

  6. REPLACE DRIVING SUPPORT ECU ASSEMBLY


    1. Replace driving support ECU assembly.

      for LHD: Click here

      for RHD: Click here

      Note

      When replacing the driving support ECU assembly, always replace it with a new one. If a driving support ECU assembly which was installed to another vehicle is used, the information stored in the driving support ECU assembly will not match the information from the vehicle. As a result, a DTC may be stored.

      Result
      Proceed to
      NEXT

    NEXT

  7. CHECK FOR DTCs (PRE-CRASH 2)


    1. Turn the power switch off and wait for at least 2 minutes.

    2. Clear the DTCs.

      Click here


      Body Electrical > Pre-Crash 2 > Clear DTCs

    3. Make sure that the DTC detection conditions are met.

      Tech Tips

      If the detection conditions are not met, the system cannot detect the malfunction.


      • Using the GTS, perform the Active Test "Stop Light Relay" with the power switch on (IG).

    4. Check for DTCs.

      Click here


      Body Electrical > Pre-Crash 2 > Trouble Codes
      Result
      Result Proceed to
      DTC C1A4B is not output (for LHD) A
      DTC C1A4B is not output (for RHD) B
      DTC C1A4B is output C

    A

    REPLACE SKID CONTROL ECU (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY) Click here

    B

    REPLACE SKID CONTROL ECU (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY) Click here

    C

    USE SIMULATION METHOD TO CHECK Click here