Zero error code 29
HVIL Open Fault
What it means
HVIL Open Fault
High Voltage Interlock Loop open - loose connection in power pack harness.
Critical — Serious issue, immediate attention required.
This is a critical fault. Do not ride until it has been resolved.
What to do
- 1Check all high-voltage connections. Dealer service recommended.
Code 29 on the other dash
The number alone is not enough. A Gen3 dash reads code 29 as HVIL Open Fault; a Gen2 dash reads the same number as BMS Isolation Danger. 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
Cypher III dash: SR/F and SR/S (2020+), DSR/X (2023+), S/F, and the S, SR, DS and DSR from 2024, when those four moved to the FST platform.
Related codes
Other Gen3 Battery/BMS codes:
What the log file records for the same subsystem:
Questions
What does error code 29 mean on a Zero Gen3 dash?
HVIL Open Fault. High Voltage Interlock Loop open - loose connection in power pack harness. It is classed as critical: serious issue, immediate attention required.
What should I do about it?
Check all high-voltage connections. Dealer service recommended.
Does code 29 mean the same thing on a Gen2 Zero?
No. On a Gen2 dash, code 29 is "BMS Isolation Danger" — 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.