Mercedes-Benz B17D249
The "Adaptive interior lighting" control unit for the rear right roof has malfunctioned. There is an internal electrical fault. Cause Software in the control units E48/3-5. Remedy
Quick answer
DTC B17D249 indicates an internal electrical fault reported by the rear-right roof Adaptive interior lighting control unit (E48/5). Verified Mercedes-Benz service information identifies software in control units E48/3-5 as the cause and specifies a software update for E48/3-5 as the remedy.
This page separates verified manufacturer/regulator evidence from supporting material. Unsupported causes, repairs or safety conclusions are not guessed.
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1. What does B17D249 mean?
DTC B17D249 indicates an internal electrical fault reported by the rear-right roof Adaptive interior lighting control unit (E48/5). Verified Mercedes-Benz service information identifies software in control units E48/3-5 as the cause and specifies a software update for E48/3-5 as the remedy.
2. Technical explanation
The verified NHTSA-posted Mercedes-Benz manufacturer communication identifies B17D249 as: “The ‘Adaptive interior lighting’ control unit for the rear right roof has malfunctioned. There is an internal electrical fault.” The communication identifies software in control units E48/3-5 as the cause. Its specified remedy is to update the software of control units E48/3-5.
3. What system is affected?
Adaptive interior lighting system, specifically the rear-right roof lamp/control unit E48/5. The verified remedy also includes control units E48/3, E48/4, and E48/5.
4. How serious is this code?
Not yet established by verified evidence.
5. Symptoms you may notice
- A stored DTC B17D249 for the rear-right roof Adaptive interior lighting control unit.
- Additional customer-visible symptoms are not yet established by verified evidence.
6. Possible causes
- Verified cause: software in control units E48/3-5.
- Other causes are not yet established by verified evidence.
7. Can I still drive the vehicle?
Not yet established by verified evidence.
8. Can I charge the vehicle?
Not yet established by verified evidence.
9. What you can safely do
- Arrange diagnosis or software-update service with a Mercedes-Benz dealer or qualified service provider.
- Do not attempt high-voltage or module repair procedures based on this information.
10. Step-by-step troubleshooting
- Confirm the presence of DTC B17D249 with appropriate diagnostic equipment.
- Check for the applicable Mercedes-Benz software update procedure for control units E48/3-5. Further troubleshooting steps are not yet established by verified evidence.
11. When to contact service
Contact a Mercedes-Benz dealer or qualified service provider to address B17D249 using the applicable software-update remedy.
12. What the service center may check
- Verify DTC B17D249 is stored for E48/5, the Adaptive rear interior lamp, roof, right.
- Determine whether the software of control units E48/3-5 requires updating.
- Perform the verified remedy: update the software of control units E48/3-5.
13. Possible repair or resolution
- Update the software of control units E48/3-5.
14. Affected vehicles
- Mercedes-Benz EQS · 2022–2023 · US
15. Related TSBs / service bulletins
- NHTSA Manufacturer Communication 11018613, Mercedes-Benz document LI82.20-P-079313, published May 22, 2025. It identifies software in E48/3-5 as the cause and directs a software update for E48/3-5.
16. Recall information
- Not yet established by verified evidence.
17. Official manufacturer information
Verified official source: NHTSA Manufacturer Communication 11018613, LI82.20-P-079313: https://static.nhtsa.gov/odi/ffdd/tsbs/TSBS_RECEIVED_2025-2026.zip#nhtsa_id=11018613. Verified applicability: 2022-2023 Mercedes-Benz EQS in the United States.
19. Frequently asked questions
What does Mercedes-Benz code B17D249 mean?
It means the rear-right roof Adaptive interior lighting control unit, E48/5, has malfunctioned and reports an internal electrical fault.
What is the verified cause of B17D249?
The cited Mercedes-Benz communication identifies software in control units E48/3-5 as the cause.
What is the verified repair for B17D249?
Update the software of control units E48/3-5.
Which vehicles are verified as applicable?
Verified applicability is 2022-2023 Mercedes-Benz EQS vehicles in the United States.
Is B17D249 a recall?
Not yet established by verified evidence.