Zero error code 29
BMS Isolation Danger
What it means
BMS Isolation Danger
Serious ground fault. BMS opened contactor for protection.
Critical — Serious issue, immediate attention required.
This is a critical fault. Do not ride until it has been resolved.
What to do
- 1Do NOT ride. Dealer service required.
Code 29 on the other dash
The number alone is not enough. A Gen2 dash reads code 29 as BMS Isolation Danger; a Gen3 dash reads the same number as HVIL Open Fault. And the model name does not settle it: the S, SR, DS and DSR kept their names when they moved from the Sevcon dash to Cypher III in 2024, so it is the year that tells you which table applies.
Which bikes use this table
Sevcon-era dash: S, SR, DS (2014-2023), DSR (2016-2023), FX (2014-2025), FXS (2016-2021), FXE (2022-2025). The SDS and XMX owner manuals print the same 0-63 table.
Related codes
Other Gen2 Battery/BMS codes:
What the log file records for the same subsystem:
Questions
What does error code 29 mean on a Zero Gen2 dash?
BMS Isolation Danger. Serious ground fault. BMS opened contactor for protection. It is classed as critical: serious issue, immediate attention required.
What should I do about it?
Do NOT ride. Dealer service required.
Does code 29 mean the same thing on a Gen3 Zero?
No. On a Gen3 dash, code 29 is "HVIL Open Fault" — a different fault entirely. The two tables share numbers but not meanings, so read the one that matches your dash, not your model name: the S, SR, DS and DSR kept their names when they moved to Cypher III in 2024.
See when this actually happened on your bike
A dash code tells you the fault; the log tells you the pack temperature, the state of charge and the ten minutes leading up to it.
Sources:
The code and its name are transcribed from Zero's own owner manuals; the severity, category and troubleshooting notes are ours. For official diagnostics, consult an authorized Zero Motorcycles dealer.