BYD P1AC400
Serious battery imbalance
Quick answer
P1AC400 is a BYD HV-battery diagnostic trouble code meaning “Serious battery imbalance.”
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 P1AC400 mean?
P1AC400 is a BYD HV-battery diagnostic trouble code meaning “Serious battery imbalance.”
2. Technical explanation
Verified technical-manual index evidence identifies P1AC400 as “Serious battery imbalance” in the HV battery system. The supplied evidence does not establish the imbalance mechanism, threshold, affected battery component, or a repair procedure.
3. What system is affected?
High-voltage (HV) battery.
4. How serious is this code?
Not yet established by verified evidence.
5. Symptoms you may notice
Not yet established by verified evidence.
6. Possible causes
- 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 assessment by a qualified BYD service provider; the supplied evidence identifies an HV-battery DTC but does not provide owner-level diagnostic or repair steps.
- Do not attempt high-voltage battery diagnosis, disassembly, or repair.
10. Step-by-step troubleshooting
- Have a qualified service provider retrieve and assess P1AC400 using appropriate BYD diagnostic information. Further troubleshooting steps are not established by the supplied verified evidence.
11. When to contact service
Service requirement is not explicitly established by the supplied evidence. Because this code concerns the HV battery, use a qualified BYD service provider for diagnosis rather than attempting HV-battery work yourself.
12. What the service center may check
- Confirm the presence and status of P1AC400. Additional service checks are not established by verified evidence.
13. Possible repair or resolution
- Not yet established by verified evidence.
14. Affected vehicles
- BYD ATTO 3 · 2022–2026 · GLOBAL
- BYD DOLPHIN · 2021–2026 · GLOBAL
- BYD HAN · 2023 · GLOBAL
15. Related TSBs / service bulletins
- No TSB or service bulletin is established by the supplied verified evidence.
16. Recall information
- No recall is established by the supplied verified evidence.
17. Official manufacturer information
Verified sources are technical-manual indexes for BYD ATTO 3, DOLPHIN, and HAN applications. They identify P1AC400 as “Serious battery imbalance.” The supplied sources do not provide manufacturer repair instructions, thresholds, driving guidance, or charging guidance.
- 17VIN technical manual index: BYD DOLPHIN diagnostic evidence · technical_manual
- 17VIN technical manual index: BYD HAN diagnostic evidence · technical_manual
- OBDTotal technical manual index: BYD ATTO 3 diagnostic evidence · technical_manual
19. Frequently asked questions
What does BYD code P1AC400 mean?
It means “Serious battery imbalance.”
Which system is associated with P1AC400?
The high-voltage battery system.
Which vehicles are supported by the supplied evidence?
BYD ATTO 3 model years 2022–2026 globally, BYD DOLPHIN model years 2021–2026 globally, and BYD HAN model year 2023 globally.
Can I drive or charge with P1AC400?
Not yet established by verified evidence.