Audi B16D4F4
left tail lamp 1 Turn signal light defective
Quick answer
Audi DTC B16D4F4 means “left tail lamp 1 Turn signal light defective.” For certain US Audi A8 and e-tron vehicles, Audi technical bulletins describe a warning message even though the turn signals remain functional; the documented technical background is a timing issue in tail-lamp software.
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 B16D4F4 mean?
Audi DTC B16D4F4 means “left tail lamp 1 Turn signal light defective.” For certain US Audi A8 and e-tron vehicles, Audi technical bulletins describe a warning message even though the turn signals remain functional; the documented technical background is a timing issue in tail-lamp software.
2. Technical explanation
Audi documentation identifies B16D4F4 as a DTC stored in the comfort control module J393 (address word 0046). In the documented bulletin condition, the instrument cluster may display a left or right rear turn-signal or tail-lamp warning while the lamps continue to operate normally. Audi attributes that documented condition to a timing issue in tail-lamp software. The supplied evidence does not establish that every occurrence of B16D4F4 has this software-related cause.
3. What system is affected?
Left tail lamp 1 turn-signal function; comfort control module J393 (address word 0046).
4. How serious is this code?
Unknown. The supplied verified evidence does not assign a severity level.
5. Symptoms you may notice
- A turn-signal or tail-lamp warning may be displayed in the instrument cluster.
- In Audi’s documented bulletin condition, the turn signals remain functional.
6. Possible causes
- For the documented bulletin condition, Audi identifies a timing issue in the tail-lamp software.
- Other causes for an individual vehicle are not yet established by verified evidence.
7. Can I still drive the vehicle?
Unknown. The supplied verified evidence does not provide a safe-to-drive determination.
8. Can I charge the vehicle?
Unknown. The supplied verified evidence does not provide a safe-to-charge determination.
9. What you can safely do
- Confirm whether the left rear turn signal operates normally.
- Arrange diagnosis by an Audi service provider if the warning or DTC is present.
- Do not assume that a functional lamp confirms the cause; Audi’s documented software condition applies only to the specified bulletin scenario.
10. Step-by-step troubleshooting
- Check whether B16D4F4 is stored in comfort control module J393, address word 0046.
- Compare the vehicle’s model year, market, and applicability with the relevant Audi bulletin.
- Have an Audi service provider evaluate whether the documented tail-lamp software timing condition applies.
11. When to contact service
Contact an Audi service provider for diagnosis and to determine whether applicable Audi service information applies to the vehicle.
12. What the service center may check
- Confirm the DTC in comfort control module J393, address word 0046.
- Verify the instrument-cluster warning and whether the turn signals remain functional.
- Verify exact vehicle applicability before applying bulletin guidance.
- Evaluate tail-lamp software relevance where the documented bulletin condition is present.
13. Possible repair or resolution
- For the documented software-timing condition, Audi bulletins describe updated/new tail-lamp software as the production solution. The supplied evidence does not establish a specific repair procedure or outcome for every vehicle with B16D4F4.
- Parts replacement is not established as necessary by the supplied evidence; one Audi bulletin notes that parts had been replaced under warranty without issues being identified.
14. Affected vehicles
- Audi A8 · 2020–2021 · US
- Audi e-tron · 2019–2020 · US
15. Related TSBs / service bulletins
- NHTSA Manufacturer Communication 10205972, published December 15, 2021: Audi communication covering a condition in which a turn-signal or tail-lamp warning may appear although lamps work normally; B16D4F4 is among the listed DTCs. https://static.nhtsa.gov/odi/tsbs/2021/MC-10205972-0001.pdf
- NHTSA Manufacturer Communication 10203693, published November 19, 2021: Audi communication describing functional rear turn signals with warning messages and a tail-lamp software timing issue; B16D4F4 is listed. https://static.nhtsa.gov/odi/tsbs/2021/MC-10203693-0001.pdf
- NHTSA Manufacturer Communication 10187587, published February 23, 2021: Audi communication describing the same warning/DTC scenario and stating that new tail-lamp software is the production solution. https://static.nhtsa.gov/odi/tsbs/2021/MC-10187587-0001.pdf
16. Recall information
- Not yet established by verified evidence.
17. Official manufacturer information
Official Audi manufacturer communications were published through NHTSA. Applicability supplied for this diagnostic is US-market Audi A8 model years 2020–2021 and Audi e-tron model years 2019–2020. Individual bulletin applicability must still be verified by exact vehicle configuration and model year.
19. Frequently asked questions
What does Audi code B16D4F4 mean?
It means “left tail lamp 1 Turn signal light defective.”
Can the warning appear while the turn signal still works?
Yes. Audi’s documented bulletin condition states that a rear turn-signal or tail-lamp warning may appear while the turn signals remain functional.
What cause does Audi identify in its bulletin?
Audi identifies a timing issue in tail-lamp software for the documented bulletin condition.
Is it safe to drive or charge with B16D4F4?
Not yet established by verified evidence.
Does B16D4F4 always mean the lamp assembly must be replaced?
No such conclusion is established by the supplied evidence. One Audi bulletin notes that parts had been replaced under warranty without issues being identified.