How a BYD fault code is built
BYD uses the standard diagnostic trouble code (DTC) format. A code like U0111 or P1A34 has five characters:
| Character | Meaning |
|---|---|
| 1st letter | P powertrain (motor, inverter, battery, engine on hybrids) · B body · C chassis (brakes, steering) · U network / communication |
| 2nd digit | 0 generic code (same meaning on every make) · 1 and up: manufacturer-specific, so you need BYD information to know the exact meaning |
| Last 3 characters | The system and the specific fault |
Many scan tools show two extra characters after the code, for example U0111-87. This is the failure type byte: it tells you how the fault happened (for example signal missing, circuit short to ground, value out of range).
Why generic code lists are not enough
BYD electric and hybrid cars use many manufacturer-specific codes for the battery management system (BMS), motor controller, on-board charger and DC-DC converter. Free online code lists usually only cover the generic P0 codes, so the description is often missing or wrong.
From code to cause in 6 steps
- Read all codes from all modules with a scan tool that supports BYD, and note them before clearing anything.
- Start with U (network) codes: a module that cannot talk can make other modules log false codes.
- Look the code up in the Diagnostic Service Manual for that model: the meaning, the set conditions and the possible causes.
- Follow the test steps in order, comparing your readings with the expected values.
- Use the wiring diagram to find connectors, pins and grounds to measure.
- Repair, clear the codes and confirm with a road test or the drive cycle described in the manual.
When there is no code
The diagnostic manual also has symptom-based procedures (for example "vehicle does not power on" or "charging stops") for faults that do not store a code.
BYD diagnostic manuals by model
Frequently asked questions
What does U0111 mean on a BYD?
U0111 is a generic network code: lost communication with the battery energy control module. On a BYD it points to the battery management system or its CAN wiring; follow the test steps in the diagnostic manual.
Can I clear BYD fault codes myself?
Yes, with a scan tool that supports BYD. Always note the codes and fix the cause first, otherwise they come back.
Are BYD fault codes the same for RHD and LHD cars?
Yes. Fault codes and diagnostic tests are the same; only the position of parts and wiring routes differ.