Large battery packs can use several monitoring devices linked together so their readings reach the main battery controller. A daisy-chain communication fault concerns that information path. It does not automatically mean the cells monitored by a missing device have failed.
The link has its own error checks
Texas Instruments documents communication error checking, including CRC, for its BQ79606A-Q1 monitor. Its supported ring arrangement can provide an alternative direction of communication after a link interruption. This is an example of a particular architecture, not a feature present in every car.
An assessment needs the actual pack design. Record which monitors are missing, whether the fault is continuous and whether any data remains available. A tool displaying zeros for unavailable information should not be read as evidence that every affected cell has zero voltage.
Keep the failure sequence
If communication changed after pack work or a software operation, retain the before-and-after reports. The order matters when distinguishing an existing fault from one that appeared during the intervention.
Send the vehicle identity and full battery scan when requesting help. Do not attempt to bridge an internal communication link from an online diagram. Isolation requirements and wiring arrangements are specific to the pack, and access requires a suitable high-voltage working procedure.
Arrange an assessment
For EV and hybrid diagnostics, send the vehicle details and fault report to AXION. We support enquiries from drivers and garages. Workshop, postal and remote options depend on the job and are confirmed before booking.
Technical reference
Read the supporting technical documentation. The referenced design or vehicle application defines its scope; it is not a universal repair procedure.
Related reading
Hall and shunt current sensors in EV battery diagnostics. Browse the automotive electronics repair library for other systems and symptoms.