LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2016 >> NX 200t Base, FWD >> Repair and Diagnosis >> Restraints >> Restraints Control Systems >> Pre-Collision System - Diagnostic Codes & Circuit Tests >> Pre-Collision System >> DTC C1A4B: Stop Light Relay Circuit [10/2014 - 09/2017] >> Description
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC C1A4B: Stop Light Relay Circuit [10/2014 - 09/2017]: Description

The brake actuator assembly (skid control ECU) sends a stop light operation signal to the stop light control ECU assembly. When the brake actuator assembly (skid control ECU) detects a malfunction in the stop light circuit, the driving support ECU assembly stores DTC C1A4B.

  Vehicle Condition
Pattern 1 Pattern 2
Diagnosis Condition +BS terminal voltage is 11 to 14 V
Stop Light illumination output (STPO) ON -
Stop Light illumination output (STPO) OFF -
Malfunction Status No signal input to STP2 terminal -
Signals input to STP and STP2 terminals do not match -
Malfunction Time 0.3 seconds or more 0.3 seconds or more
Number of Trips - -
DTC No. Detection Item DTC Detection Condition Trouble Area
C1A4B Stop Light Relay Circuit Either of the following conditions is met:
  • When the engine switch is on (IG), 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. (Pattern 1)
  • When the engine switch is on (IG), 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. (Pattern 2)
  • Brake actuator assembly (skid control ECU)
  • Stop light control ECU assembly
  • Rear combination light assembly LH
  • Rear combination light assembly RH
  • Rear light assembly LH
  • Rear light assembly RH
  • Center stop light assembly
  • Harness or connector