B14C2

Code

Generic B — Body

Energy Storage System Communication Fault (Bus B)

Brand: Generic

Type: B — Body

Views: UK: 10 EN: 15 RU: 14

AI status

Completed

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Page language: EN

Causes

Damaged or shorted CAN wiring (CAN_H or CAN_L) on Bus B
Loose, corroded, or improperly seated connector at the ESS or another module on Bus B
Failed or intermittent power supply or ground to the ESS control module
Missing or failed bus termination resistor(s)
Faulty ESS control module (BMS) or other module on Bus B
Software/configuration mismatch or module firmware fault

Symptoms

ESS/BMS not visible or responding in scan tool on Bus B
Battery/charge/discharge disabled or limited (reduced power or limp mode)
HV/EV system warning lamp or multiple system warning lights
Charging fault, inability to start charging, or charging aborted
Reduced regenerative braking or driveability limitations
Intermittent faults that may clear and reappear

What to check

Read all stored and pending DTCs on relevant control modules; note freeze frame data and occurrence pattern
Verify vehicle battery/low-voltage supply and relevant fuses and relays
Visually inspect ESS connectors, harnesses, and Bus B wiring for damage, corrosion, or water ingress
Check grounds for security and corrosion at ESS and chassis ground points
Measure CAN_H and CAN_L voltages at ESS connector and at several points along Bus B (idle and during bus activity)
Check termination resistance across CAN_H and CAN_L with key off (expect ~60 ohm if two 120Ω terminators in parallel or ~120Ω depending on architecture)

Signal parameters

Vehicle low-voltage supply to ESS: approximately 11–15 V (varies by vehicle)
CAN bus idle voltages: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (single-ended)
CAN dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V; differential ~2 V
Expected termination resistance between CAN_H and CAN_L: typically ~60 Ω (two 120 Ω terminators in parallel) or ~120 Ω for single terminator designs; consult wiring diagram
No short to battery positive or ground on CAN pair (measure high resistance to +B and ground)

Diagnostic algorithm

Connect a professional scan tool and retrieve all DTCs and freeze frame data from ESS and gateway modules; record occurrence conditions (ignition state, charging, driving).
Verify low-voltage battery and ESS module supply fuses/relays are present and intact; restore any blown fuses and re-test.
Visually inspect ESS connectors, bus connectors, and harness for damage, corrosion, or moisture. Reseating connectors may clear intermittent faults; inspect pins for corrosion or bent pins.
With ignition off, measure termination resistance between CAN_H and CAN_L at multiple points on Bus B. Compare with specification from wiring diagram.
With ignition on and modules awake, use multimeter to measure CAN_H and CAN_L single-ended voltages at ESS connector; then use an oscilloscope or CAN analyzer to check waveform quality for noise, missing messages, stuck dominant, or reflections.
If bus short or open suspected, perform continuity and short-to-power/ground checks on CAN pair between ESS and gateway. Repair any damaged wiring or connectors.
Isolate the fault by disconnecting suspect modules one at a time (follow vehicle-specific procedures and safety for HV systems) to see when the bus returns to normal — this identifies a faulty node.
If a single module is identified, verify its power/ground and attempt reprogramming or replacement per manufacturer procedure. Update module firmware if TSBs or calibrations exist.
After repairs, clear codes and verify communication is restored under all operating conditions (key cycles, charging, driving). Confirm no additional related codes appear.
Follow high-voltage safety procedures when working on ESS components. Only qualified technicians should perform HV system isolation and repairs.

Likely causes

Loose or corroded connector at the ESS control module
Open/short in CAN pair near ESS harness or connector
Failed ESS module or its internal transceiver
Blown fuse or poor ground affecting ESS module power

Fault status

⚠️ Status

Communication fault detected between vehicle network and the Energy Storage System on Bus B. Messages missing, corrupted, or intermittent—may disable charging or HV operation until resolved.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours