Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSLEXUS2012CT 200H L4-1.8L (2ZR-FXE) HYBRIDREPAIR AND DIAGNOSISA L L DIAGNOSTIC TROUBLE CODES ( DTC )TESTING AND INSPECTIONC CODE CHARTSC1A4BPRE-COLLISION SYSTEM
2012 Lexus CT 200h L4-1.8L (2ZR-FXE) Hybrid
Pre-Collision System
2012 Lexus CT 200h L4-1.8L (2ZR-FXE) HybridSECTION Pre-Collision System
PRE-COLLISION: PRE-COLLISION SYSTEM: C1A4B: Stop Light Relay Circuit
C1A4B - Stop Light Relay Circuit
DESCRIPTION
The stop light switch assembly sends a brake pedal operation signal to the driving support ECU. Based on the signal, the driving support ECU cancels cruise control.
INSPECTION PROCEDURE
NOTICE:
When this DTC is output, malfunction in the lighting system is suspected. Check if the lighting system is functioning normally How To Proceed With Troubleshooting.
PROCEDURE
1. CHECK DTC OUTPUT (ELECTRONICALLY CONTROLLED BRAKE SYSTEM)
(a) Check DTC for electronically controlled brake system Reading and Clearing Diagnostic Trouble Codes.
OK:
Electronically controlled brake system DTC is not output.
NG -- GO TO ELECTRONICALLY CONTROLLED BRAKE SYSTEM How To Proceed With Troubleshooting
OK -- Continue to next step.
2. REPLACE BRAKE BOOSTER WITH MASTER CYLINDER
(a) Replace the brake booster with master cylinder (skid control ECU) Removal.
NEXT -- Continue to next step.
3. CHECK DTC OUTPUT (PRE-COLLISION SYSTEM)
(a) Using the Techstream, enter the following menus: Body Electrical / Pre-Collision 2 / Trouble Codes.
(b) Clear the DTCs Pre-Collision System.
(c) Check for DTCs.
OK:
DTC U0122 is not output.
NG -- GO TO CAN COMMUNICATION SYSTEM How to Proceed With Troubleshooting
OK -- REPLACE DRIVING SUPPORT ECU Removal
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.