U064A: Lost Communication With Hybrid/EV Battery Pack Current Sensor A

What it means

A control module has stopped receiving expected network messages from hybrid/EV battery pack current sensor A. The effect on battery current monitoring and control depends on the vehicle's system design.

At a glance

• Usually lights the warning light of the system that lost communication
• The engine or gearbox may go into limp mode

How it works

Hybrid/EV battery pack current sensor A measures current flowing into or out of the high-voltage battery pack and reports it over the vehicle network. U064A sets when a control module stops receiving expected messages from sensor A, which can impair battery-current monitoring and lead to limited hybrid or electric operation.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

Symptoms

• Warning light or message related to the affected system
• Battery current data may be unavailable

How to diagnose it

1. Scan all modules and save freeze-frame data, noting any high-voltage battery, current-sensor, isolation, or communication codes.
2. Check live data for battery pack current sensor A and related battery data to confirm whether sensor A’s messages are missing.
3. Inspect only accessible low-voltage connectors and network wiring associated with sensor A for damage or corrosion; do not disturb high-voltage components.
4. Have the sensor module’s low-voltage power and ground checked against the manufacturer’s specification.
5. Test the network wiring serving sensor A for opens or shorts using the vehicle wiring information.
6. If wiring and supplies pass, verify network communication and sensor-module operation using the manufacturer’s procedure.

Common fixes

• Reconnect or clean an accessible low-voltage connector for current sensor A.
• Repair damaged low-voltage network wiring to sensor A.
• Restore the sensor module’s low-voltage power or ground supply.
• Replace the current sensor A module if its wiring and supplies are sound and it remains unresponsive.

Can I keep driving?

Treat a hybrid-system, battery, or reduced-power warning as a reason to stop safely and follow the vehicle’s instructions; loss of current monitoring can limit or interrupt propulsion. Do not access high-voltage components, and arrange prompt diagnosis.