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Home >> Toyota >> 2021 >> 4Runner TRD Pro >> Repair and Diagnosis (Single Page) >> Restraints >> Restraints Control Systems >> Pre-Collision System - Diagnostic Codes & Circuit Tests >> Pre-Collision System >> DTC C1A4B: Stop Light Relay Circuit [08/2019 - ] >> Description
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DTC C1A4B: Stop Light Relay Circuit [08/2019 - ]: 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. *1: for Hydraulic Brake Booster
  2. *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. *1: for Hydraulic Brake Booster
  2. *2: for Vacuum Brake Booster