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Home >> Toyota >> 2017 >> Prius C Two >> 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 [11/2015 - ] >> Description
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DTC C1A4B: Stop Light Relay Circuit [11/2015 - ]: 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 pre-collision city sensor stores DTC C1A4B.

DTC No. DTC Detection Condition Trouble Area
C1A4B
  • All of the following conditions are met:
    • 3 seconds have elapsed since the power switch was turned on (IG).
    • The auxiliary battery voltage is 10 V or more for 3 seconds or more.
    • Communication between the pre-collision city sensor and skid control ECU (brake booster with master cylinder assembly) is normal.
    • The pre-collision city sensor receives a stop light relay circuit malfunction signal from the skid control ECU (brake booster with master cylinder assembly) for 1 second or more.
  • Lighting system
  • Electronically controlled brake system
  • Skid control ECU (Brake booster with master cylinder assembly)
  • Stop light relay (Stop light switch assembly)
  • Wire harness or connector