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.
2018 Lexus GS FFACTORY OEM SERVICE PROCEDURE
Lighting System
LIGHTING SYSTEM DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION
| DTC Code | Description |
|---|---|
| B1244 | Light Sensor Circuit Malfunction |
| B242C | Right Headlight ECU Malfunction |
| B242D | Left Headlight ECU Malfunction |
| B242E | Open in IG Circuit |
| B2439 | Headlamp LH Circuit |
| B243A | Headlamp RH Circuit |
| B243B | LED Wiring for High Beam LH Circuit |
| B243C | LED Wiring for High Beam RH Circuit |
| B243D | Left Low Beam Fan Malfunction |
| B243E | Right Low Beam Fan Malfunction |
| B2456 | Left Headlight ECU Variation Error |
| U0073 | Control Module Communication Bus OFF |
| U0100 | Lost Communication with ECM / PCM "A" |
| U0129 | Lost Communication with Brake System Control Module |
| U0142 | Lost Communication with Body Control Module "B" |
| U0155 | Lost Communication with Instrument Panel Cluster (IPC) Control Module |
| U0242 | Lost Communication With Headlamp Control Module "B" |
| U1000 | CAN Communication Failure (Message Registry) |
Factory Service Tools
Use the Manual With the Right Hardware
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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.
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