U064A

Code

Generic U — Network/User

Lost Communication With Hybrid/EV Battery Pack Current Sensor A

Brand: Generic

Type: U — Network/User

Views: UK: 18 EN: 32 RU: 19

AI status

Completed

ready

Completed 100%

Page language: EN

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