Toyota Tundra Service Manual: Stop Light Relay Circuit (C1A4B)

Toyota Tundra Service Manual / Vehicle Interior / Pre-collision / Pre-collision System / Stop Light Relay Circuit (C1A4B)

DESCRIPTION

The skid control ECU (brake actuator assembly) sends a stop light operation request signal to the stop light relay (stop light switch assembly). If the skid control ECU (brake actuator assembly) detects a malfunction in the stop light relay circuit, the millimeter wave radar sensor assembly stores DTC C1A4B.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

C1A4B

Stop Light Relay Circuit

While the ignition switch is ON, the millimeter wave radar sensor assembly receives a stop light relay circuit malfunction signal from the skid control ECU (brake actuator assembly) for 1 second or more.
  • Vehicle stability control system
  • Millimeter wave radar sensor assembly

CAUTION / NOTICE / HINT

NOTICE:

  • When replacing the millimeter wave radar sensor assembly, always replace it with a new one. If a millimeter wave radar sensor assembly which was installed to another vehicle is used, the information stored in the millimeter wave radar sensor assembly will not match the information from the vehicle. As a result, a DTC may be stored.
  • If the millimeter wave radar sensor assembly has been replaced, be sure to perform millimeter wave radar sensor assembly adjustment.

    Click here

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

    Click here

PROCEDURE

1.

CHECK FOR DTCs (VEHICLE STABILITY CONTROL SYSTEM)

HINT:

Pre-collision system DTC C1A4B may be stored due to a malfunction in the vehicle stability control system. Therefore, it is necessary to check for and troubleshoot vehicle stability control system DTCs first.

(a) Check for DTCs.

Click here

Result

Proceed to

Vehicle stability control system DTCs are not output

A

Vehicle stability control system DTCs are output

B
B

GO TO VEHICLE STABILITY CONTROL SYSTEM

A

2.

CHECK FOR DTCs (PRE-COLLISION SYSTEM)

(a) Clear the DTCs.

Click here

(b) Make sure that the DTC detection conditions are met.

HINT:

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

(c) Check for DTCs.

Click here

Result

Proceed to

DTC C1A4B is not output

A

DTC C1A4B is output

B
A

USE SIMULATION METHOD TO CHECK

B

REPLACE MILLIMETER WAVE RADAR SENSOR ASSEMBLY

    Skid Control Buzzer Circuit (C1A4A)

    Front Radar Sensor (C1A10)

    See More:

    Toyota Tundra Service Manual > Forward Recognition Camera System: Steering Angle Sensor (C1A47)
    DESCRIPTION The forward recognition camera receives steering angle information from the spiral with sensor cable sub-assembly. If the forward recognition camera detects a spiral with sensor cable sub-assembly malfunction, DTC C1A47 is stored. DTC No. Detection Item DTC Detection Condition Trouble Ar ...

    Toyota Tundra Owners Manual

    Toyota Tundra Service Manual

    © 2026 Copyright www.ttundra.com
    0.0343