Code
U064A
Generic
U — Network/User
Lost Communication With Hybrid/EV Battery Pack Current Sensor A
Views:
UK: 15
EN: 20
RU: 15
AI status
Completed
Completed
100%
Causes
- Open or short in communication wiring (CAN or LIN) between sensor/module and vehicle network
- Faulty Battery Management System (BMS) or battery pack current sensor module
- Loss of power or ground to the sensor or BMS (blown fuse, relay, connector)
- Corroded, damaged, or loose connectors at the battery pack or harness
- Bus termination or wiring impedance problem (missing/failed termination resistors)
- Intermittent wiring/harness damage due to vibration, chafing or water ingress
Symptoms
- Malfunction Indicator Lamp (MIL) or dash warning for hybrid/EV system
- Reduced hybrid/EV performance or entry to limp mode
- Inability to charge or limited regenerative braking
- Incorrect or missing battery current/SOC readings on dash or data stream
- Related communication U-codes present (other modules report lost messages)
What to check
- Read vehicle network for U064A and any related U or B codes; capture freeze-frame and time stamps
- Check for other modules reporting bus off or communication faults
- Visually inspect connectors, pins and harness at the battery pack and along the wiring route for damage, corrosion or water
- Verify fuses and relays that supply the sensor/BMS power and grounds
- Use a scan tool to view live data and confirm if the current sensor A data stream is present or blank
- Measure power and ground at the sensor/BMS connector with a DMM
Signal parameters
- CAN bus common-mode idle ~2.5 V (CAN_H ≈2.5 V, CAN_L ≈2.5 V); dominant state: CAN_H ≈3.5 V, CAN_L ≈1.5 V
- Typical CAN differential idle ≈0 V, dominant differential ≈2.0 V
- Message expected periodically while pack is awake — frequency depends on vehicle (commonly 10–1000 ms intervals)
- Data payload: digital CAN message containing battery pack current, direction, and diagnostic flags (format varies by manufacturer)
- Termination resistance ~60 ohms between CAN_H and CAN_L (two 120 ohm resistors in parallel)
Diagnostic algorithm
- Connect a capable scan tool and record U064A plus any other network codes. Note when code first occurred and whether it is active or stored.
- Attempt to read live data for Battery Pack Current Sensor A. If no data, attempt to command or wake the BMS per vehicle procedures.
- Perform a visual inspection of the high-voltage battery pack connector area and routing for the communication harness. Look for corrosion, pushed-out pins, water intrusion, or harness damage.
- Verify fuses and relay function for BMS/sensor power circuits. Restore or replace any failed power components and re-test.
- Check grounds for low resistance to chassis and battery negative. Repair high-resistance grounds.
- With appropriate safety precautions for HV systems, back-probe the sensor/BMS communication connector and measure CAN_H and CAN_L voltages with an oscilloscope while the vehicle is awake. Look for valid idle levels and normal differential waveforms.
- If CAN physical layer is faulty (missing waveform, dominant stuck, excessive noise), isolate segments to locate short/open (disconnect battery pack connector and re-check).
- Measure continuity between sensor/module pins and the central gateway/ECU to confirm no open circuits. Repair wiring or connectors as needed.
- If wiring and power/grounds are good but no messages originate from the sensor, consider replacing the current sensor module or BMS per factory procedure or consult manufacturer service information for module replacement/testing.
- After repairs, clear codes, perform system initializations (if required), and road test to verify proper communication and restore normal hybrid/EV operation.
- If intermittent or unresolved, review technical service bulletins and consider software/firmware updates for network modules.
Likely causes
- Disconnected or corroded connector at the battery pack current sensor
- Failed current sensor module inside the battery pack
- Open/shorted CAN High or CAN Low wiring in the battery pack harness
- Blown fuse or poor ground for the BMS or sensor power supply
- Failed BMS/controller that publishes current sensor messages
- Missing CAN termination resistor or short to chassis affecting bus levels
Fault status
Status
Lost communication with Hybrid/EV Battery Pack Current Sensor A — expected CAN/LIN messages missing or invalid. May disable hybrid functions and trigger related warnings.
Repair difficulty: Medium
Diagnostic time: 1.0 - 3.5 hours
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