Toyota Tacoma (2015-2018) Service Manual: Stop Light Relay Circuit (C1A4B)

Toyota Tacoma (2015-2018) Service Manual / Pre-collision / Pre-collision System / Stop Light Relay Circuit (C1A4B)

DESCRIPTION

The skid control ECU (master cylinder solenoid)*1 or skid control ECU (brake actuator assembly)*2 sends a stop light operation request signal to the stop light relay (stop light switch assembly). If the skid control ECU (master cylinder solenoid)*1 or skid control ECU (brake actuator assembly)*2 detects a malfunction in the stop light relay circuit, the millimeter wave radar sensor assembly stores DTC C1A4B.

*1: for Hydraulic Brake Booster
*2: for Vacuum Brake Booster

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 (master cylinder solenoid)1 or skid control ECU (brake actuator assembly)2 for 1 second or more.	Vehicle stability control system Millimeter wave radar sensor assembly

*1: for Hydraulic Brake Booster
*2: for Vacuum Brake Booster

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

GO TO VEHICLE STABILITY CONTROL SYSTEM

2.	CHECK FOR DTCs (PRE-COLLISION SYSTEM)

(a) Clear the DTCs.

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

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

HINT:

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

Click here

Result	Proceed to
DTC C1A4B is not output	A
DTC C1A4B is output	B

USE SIMULATION METHOD TO CHECK

REPLACE MILLIMETER WAVE RADAR SENSOR ASSEMBLY

Skid Control Buzzer Circuit (C1A4A)

DESCRIPTION The millimeter wave radar sensor assembly is connected to the forward recognition camera via CAN communication. The millimeter wave radar sensor assembly operates the pre-collision ala ...

Steering Angle Sensor (C1A47)

DESCRIPTION The millimeter wave radar sensor assembly receives steering angle information from the steering angle sensor (spiral cable with sensor sub-assembly). If the millimeter wave radar sens ...

Other materials:

Brake Switch "A" Circuit Open (P057113)
DESCRIPTION DTC No. DTC Detection Condition Trouble Area MIL Note P057113 Vehicle Condition: Cruise control operating Malfunction Status: Stop light switch assembly circuit malfunction ...

Inspection
INSPECTION PROCEDURE 1. INSPECT TRANSMISSION WIRE (a) Measure the resistance according to the value(s) in the table below. Text in Illustration *a Component without harness connected (Transmission Wire) Standard Resistance: ...

Theft deterrent system
Engine immobilizer system The vehicle’s keys have built-in transponder chips that prevent the engine from starting if the key has not been previously registered in the vehicle’s on-board computer. Never leave the keys inside the vehicle when you leave the vehicle. The indicator light fl ...