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Home >> Lexus >> 2017 >> GS 350 Base, AWD >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Cruise Control Systems >> Dynamic Radar Cruise Control System (Diagnostic Codes & Circuit Tests) >> Dynamic Radar Cruise Control System >> DTC C1A4B: Stop Light Relay Circuit [10/2015 - 09/2017] >> Description

DTC C1A4B: Stop Light Relay Circuit [10/2015 - 09/2017]: Description

The skid control ECU (brake actuator assembly) sends a stop light operation request signal to the No. 2 integration relay (stop light relay). If the skid control ECU (brake actuator assembly) detects a malfunction in the stop light relay 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 vehicle speed is approximately 50 km/h (30 mph) or more, the cruise control switch (ON/OFF) is on, the +BS 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 vehicle speed is approximately 50 km/h (30 mph) or more, the cruise control switch (ON/OFF) is on, the +BS 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
  • Skid control ECU (brake actuator assembly)
  • No. 2 integration relay (Stop light relay)
  • Harness or connector