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.
DTC B242C-04: Headlight Control Module (Sub) System Internal Failure; DTC B242D-04: Headlight Control Module (Main) System Internal Failure [11/2023 - ]: Procedure
- CLEAR DTC
- Clear the DTCs.
Body Electrical > Headlight Control > Clear DTCs
Body Electrical > Headlight Control (Sub) > Clear DTCs
Result
Proceed to NEXT
Result:
NEXT
See step 2
- Clear the DTCs.
- CHECK FOR DTC
- Turn the ignition switch to ON.
- Wait at least 15 minutes.
- Check for DTCs.
Body Electrical > Headlight Control > Trouble Codes
Body Electrical > Headlight Control (Sub) > Trouble Codes
OK
DTC B242C-04 and B242D-04 are not output.
Result
Result Proceed to OK A NG (DTC B242C-04 is output) B NG (DTC B242D-04 is output) C
Result:
A
USE SIMULATION METHOD TO CHECK. Refer to HOW TO PROCEED WITH TROUBLESHOOTING [12/2019 - ]
Result:
B
REPLACE HEADLIGHT ECU SUB-ASSEMBLY RH. Refer to REMOVAL [11/2023 - ]
Result:
C
REPLACE HEADLIGHT ECU SUB-ASSEMBLY LH. Refer to REMOVAL [11/2023 - ]
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.