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BYD U20B400

BIC5 CAN communication timeout

DriveUnknown. Verified evidence does not establish whether the vehicle is safe to drive with U20B400.
ChargeUnknown. Verified evidence does not establish whether the vehicle is safe to charge with U20B400.
ServiceService need is unknown in the verified record. Because this is an HV battery/network communication code and no safe operating status is established, professional diagnosis is appropriate.
Confidence95%

Quick answer

BYD DTC U20B400 means “BIC5 CAN communication timeout.” Verified evidence identifies it as an HV battery/network diagnostic code, but does not establish the specific fault cause, vehicle behavior, or repair.

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 U20B400 mean?

BYD DTC U20B400 means “BIC5 CAN communication timeout.” Verified evidence identifies it as an HV battery/network diagnostic code, but does not establish the specific fault cause, vehicle behavior, or repair.

2. Technical explanation

A CAN communication timeout means the diagnostic system recorded a loss or timeout of expected communication involving BIC5 on the vehicle network. The supplied evidence does not define BIC5 further, identify the failed component, or provide diagnostic thresholds or test procedures.

3. What system is affected?

HV battery/network.

4. How serious is this code?

Unknown. The verified diagnostic record lists severity as unknown.

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?

Unknown. Verified evidence does not establish whether the vehicle is safe to drive with U20B400.

8. Can I charge the vehicle?

Unknown. Verified evidence does not establish whether the vehicle is safe to charge with U20B400.

9. What you can safely do

  • Do not attempt high-voltage battery or network repairs based on this code alone.
  • Arrange professional diagnosis if the code is present or returns.
  • Not yet established by verified evidence whether any additional owner actions are appropriate.

10. Step-by-step troubleshooting

  1. A qualified service provider should diagnose U20B400 using vehicle-specific procedures. The supplied verified evidence does not provide further troubleshooting steps.

11. When to contact service

Service need is unknown in the verified record. Because this is an HV battery/network communication code and no safe operating status is established, professional diagnosis is appropriate.

12. What the service center may check

  • Confirm the presence and status of U20B400 with compatible diagnostic equipment.
  • Use BYD model-specific diagnostic information to investigate the BIC5 CAN communication timeout.
  • Further service checks are not yet established by verified evidence.

13. Possible repair or resolution

  • Not yet established by verified evidence.

14. Affected vehicles

15. Related TSBs / service bulletins

  • Not yet established by verified evidence.

16. Recall information

  • Not yet established by verified evidence.

17. Official manufacturer information

Verified technical-manual-index evidence identifies U20B400 as “BIC5 CAN communication timeout” for specified BYD applications. The supplied sources are: OBDTotal technical manual index for BYD ATTO 3 / Yuan Plus (SC2E), and 17VIN technical manual index entries for BYD DOLPHIN and BYD HAN.

19. Frequently asked questions

What does BYD code U20B400 mean?

It means “BIC5 CAN communication timeout.”

Which BYD 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 U20B400?

Not yet established by verified evidence. The diagnostic record marks both driving and charging status as unknown.

What repair fixes U20B400?

Not yet established by verified evidence. The supplied sources identify the code meaning but do not provide a verified repair resolution.

20. Sources & verification

Verified
BYD U20B400: BIC5 CAN communication timeout | EV Diagnostics