U064B

Code

Generic U — Network/User

Lost Communication With Hybrid/EV Battery Pack Current Sensor B

Brand: Generic

Type: U — Network/User

Views: UK: 20 EN: 40 RU: 23

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Page language: EN

Causes

Open, shorted, or high-resistance wiring between sensor B and the BMS/ECU
Corroded, damaged, or poorly seated connector at sensor B or BMS
Blown fuse or failed power/ground for the sensor
Faulty Battery Pack Current Sensor B
Loss of or intermittent CAN/LIN bus communication (termination, wiring, or module failure)
BMS/ECU software fault or internal module failure

Symptoms

Hybrid/EV system warning lamp and/or battery warning lamp illuminated
Reduced hybrid/electric drive performance or limp-home mode
Inaccurate or missing battery current/SOC readouts on dash or scan tool
Inability to charge/discharge battery normally
Stored DTCs related to BMS and communications

What to check

Pull stored codes and freeze-frame data with a capable scan tool; note any additional BMS or CAN-related codes
Visually inspect connectors, pins and harness for damage, corrosion, or contamination at sensor B and BMS connector
Verify main battery pack isolation is safe and follow all high-voltage safety procedures before probing near HV components
Check related fuses and relays for continuity and correct supply voltage
Use a scan tool to confirm presence/absence of sensor B data frames on the network
Perform a wiggle test on harness while monitoring the network for intermittent communication

Signal parameters

CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (differential 0 V when recessive; dominant differential typically ≈ 2 V–3.5 V)
Common CAN bit rates: 250 kbps or 500 kbps (vehicle-specific)
Sensor supply: typically 5 V reference or switched 12 V supply (check OEM diagram)
Sensor output: either periodic CAN messages from the sensor or an analog voltage proportional to pack current (0–5 V) depending on design
Expected message frequency: periodic BMS/current messages every few 10s–100s of ms (OEM-specific)

Diagnostic algorithm

Retrieve DTCs and related codes. Record freeze-frame and note other modules reporting communication errors.
Confirm vehicle is in a safe state for inspection. Follow all manufacturer high-voltage safety procedures before accessing the battery pack or HV wiring.
Visually inspect connectors, wiring, and harness routing to Sensor B and the BMS for damage, corrosion, or loose pins.
Check fuses/relays that supply sensor power. Replace any blown fuses and verify power is present when system is on.
With low-voltage safety measures in place, back-probe the sensor connector and verify supply voltage and ground continuity to the sensor.
Use a scan tool to determine whether Sensor B messages are present on the CAN bus. If messages are absent, attach an oscilloscope or CAN sniffer and monitor CAN_H/CAN_L for traffic and valid differential signals.
If the sensor uses an analog output, measure the output voltage while commanding known loads or with vehicle powered to verify the signal changes with battery current.
Perform a wiggle/test under load: probe communication while moving harness and connectors to check for intermittent faults.
If wiring and connectivity are good but no messages/signals appear, disconnect and test/replace Sensor B per OEM procedure or swap with Sensor A (if identical) to determine if the sensor is faulty.
If swapping indicates module-side fault, inspect BMS/ECU connectors and wiring back to the module. Check CAN termination resistors and other modules on the same bus for faults.
Clear codes and re-test. If DTC returns, consult manufacturer service information for module reprogramming or module replacement procedures.
Document all steps and replace faulty components. After repair, confirm proper communication and vehicle functionality with extended road test and scan tool verification.

Likely causes

Connector corrosion at the battery sensor or BMS
Chafed harness or pinched wire in the battery pack area
Failed sensor electronics (internal failure)
CAN bus fault (missing termination, short to battery/ground)
Blown fuse or bad relay supplying sensor power
Recent service or collision damage to battery wiring

Fault status

⚠️ Status

Lost communication with Hybrid/EV Battery Pack Current Sensor B — BMS not receiving current data from Sensor B over the vehicle network; functionality may be limited.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours