Fault Simulation Testing for New Energy Vehicles: Technical Methods, Standards, and Applications

Fault simulation testing is a critical validation process for new energy vehicles (NEVs), systematically injecting electrical, communication, and sensor faults into battery systems, drive units, and electronic controls to verify fail-safe behavior and diagnostic performance. Conducted by accredited third-party laboratories and OEM engineering teams, this testing supports compliance with functional safety standards such as ISO 26262 and electric vehicle safety standards including ISO 6469, GB/T 18384, and GB 38031. This article explains the technical principles, sample types, test items, methodologies, and practical applications of fault simulation testing for electric and hybrid vehicles.

Technical Overview

Fault simulation testing, also known as fault injection testing, is a structured validation technique used to evaluate the safety, robustness, and diagnostic capability of new energy vehicle systems. Instead of waiting for faults to occur naturally during road operation, engineers deliberately introduce controlled faults—such as short circuits, open circuits, insulation degradation, sensor signal anomalies, and communication interruptions—into vehicle subsystems under laboratory conditions. The purpose is to observe whether the system detects the fault, responds within the required fault tolerant time interval (FTTI), transitions to a defined safe state, and prevents hazardous events such as thermal runaway, unintended torque, or loss of propulsion.

This testing methodology is fundamental to functional safety engineering. Under ISO 26262 (Road Vehicles – Functional Safety), fault injection is a required verification activity for systems with high Automotive Safety Integrity Levels (ASIL). It is also central to the safety validation of high-voltage systems specified in ISO 6469, GB/T 18384, UN ECE Regulation No. 100, and battery safety requirements under GB 38031 and IEC 62660. In addition, communication fault testing supports robustness requirements described in ISO 11898 (CAN), AUTOSAR E2E protection concepts, and cybersecurity validation under ISO/SAE 21434.

A complete fault simulation program typically combines three levels of testing: component-level fault injection on a test bench, hardware-in-the-loop (HIL) simulation integrating real electronic control units with simulated plant models, and vehicle-level or system-level fault testing in controlled laboratory environments with high-voltage safety interlocks, fire suppression, and full data acquisition.

Testing Samples

High-Voltage Battery Systems

Battery packs, battery modules, battery management systems (BMS), and related sensing and protection circuits constitute a primary category of test samples. Fault simulation verifies that the BMS correctly detects cell voltage anomalies, temperature sensor failures, insulation faults, and contactor malfunctions, and that the pack enters a safe state without triggering thermal events.

Electric Drive Systems

Drive motors, motor controllers (inverters), and integrated e-axles are tested for phase short circuits, gate driver failures, rotor position sensor faults, and over-temperature conditions. The objective is to confirm torque derating, shutdown strategies, and protection against unintended acceleration or loss of drive.

Power Electronics and Charging Components

On-board chargers (OBC), DC-DC converters, high-voltage distribution units (PDU), charging interfaces, and charging control units are subjected to input voltage transients, output short circuits, ground faults, and charging communication faults to verify protection coordination and safe charge termination.

Electronic Control Units and Domain Controllers

Vehicle control units (VCU), battery management controllers, body controllers, and zone/domain controllers are evaluated for communication loss, corrupted messages, power supply interruptions, and internal watchdog failures to validate diagnostic coverage and fail-operational or fail-safe behavior.

Sensors, Wiring Harnesses, and Actuators

Current sensors, voltage sensors, temperature sensors, high-voltage interlock loops (HVIL), contactors, pre-charge circuits, relays, connectors, and wiring harnesses are tested for signal drift, stuck-at faults, intermittent contact, and open or short conditions that may occur over the vehicle lifetime.

Thermal Management Components

Coolant pumps, electric heaters, heat pump systems, fans, and thermal sensors are evaluated for pump stall, heater over-temperature, coolant loss, and cooling control failures that could lead to battery or power electronics overheating.

Testing Items

Typical fault simulation test items cover electrical, signal, communication, thermal, and mechanical failure modes:

• Short circuit faults: phase-to-phase short, phase-to-ground short, positive-to-negative terminal short, and output short circuit conditions.
• Open circuit faults: broken conductors, disconnected connectors, open sensor lines, and open contactor coils.
• Insulation faults: reduced insulation resistance between high-voltage circuits and the chassis, and intermittent insulation breakdown per ISO 6469-1 and GB/T 18384.
• Ground faults and earth leakage simulation on high-voltage bus lines.
• Overvoltage, undervoltage, and voltage transient disturbances on power supply and high-voltage rails.
• Overcurrent and overload conditions, including locked rotor and stall scenarios.
• Contactor faults: contact welding, failure to open, failure to close, and pre-charge circuit malfunction.
• Sensor signal faults: out-of-range values, stuck-at signals, signal drift, ripple, and implausible value combinations.
• Communication faults: CAN/LIN bus-off, message loss, delayed or duplicated frames, incorrect checksums, alive counter errors, and spoofed messages.
• High-voltage interlock loop (HVIL) interruption and short circuit conditions.
• Thermal faults: temperature sensor failure, over-temperature events, cooling system failure, and heater runaway.
• Intermittent and vibration-induced faults, including contact bounce and loose terminal behavior.
• Combined and cascaded fault scenarios representing realistic multi-point failures.

Testing Methods

Fault simulation testing is executed using a layered methodology that progresses from simulation environments to physical fault insertion on real hardware:

• Hardware-in-the-loop (HIL) fault injection: Real controllers are connected to a real-time simulator running plant models of the battery, motor, and vehicle. Faults such as sensor failures and communication errors are injected through the simulation environment, enabling safe, repeatable testing of dangerous scenarios.
• Electrical fault injection with fault insertion units (FIU): Break-out boxes and relay-based fault matrices are inserted into wiring harnesses, allowing engineers to switch in short circuits, open circuits, and resistive faults with precise timing while monitoring system response with oscilloscopes and data loggers.
• Insulation and ground fault simulation: Programmable resistor banks are connected between high-voltage conductors and the chassis to simulate graduated insulation degradation, verifying insulation monitoring thresholds and warning strategies required by ISO 6469 and GB/T 18384.
• Communication fault injection: Bus analyzers and network disturbance tools corrupt, delay, block, or replay CAN, CAN-FD, and LIN messages to evaluate E2E protection mechanisms, timeout monitoring, and degradation concepts.
• Environmental combined testing: Fault injection is combined with temperature, humidity, and vibration profiles in environmental chambers to reproduce faults that emerge only under environmental stress, aligned with IEC 60068 test procedures.
• Vehicle-level fault testing: On complete vehicles or vehicle buck rigs, faults are introduced at connectors, sensors, and control units while the vehicle operates on chassis dynamometers or lifts, with high-voltage safety protocols, remote shutdown capability, and fire protection in place.

Throughout testing, engineers record diagnostic trouble codes (DTCs), fault detection times, torque or power limitation responses, warning lamp activation, high-voltage shutdown behavior, and recovery after fault removal. Pass criteria are typically defined as: detection of the injected fault within the fault tolerant time interval, achievement of the defined safe state, no fire, explosion, thermal runaway, or electric shock hazard, and correct recovery behavior when the fault is cleared.

Applications

Fault simulation testing serves multiple engineering and compliance objectives across the vehicle development lifecycle:

• Functional safety validation: Demonstrating compliance with ISO 26262 safety requirements, including diagnostic coverage targets for ASIL B, C, and D systems and verification of safety mechanisms identified in the Functional Safety Concept.
• Regulatory and market access testing: Supporting type approval and conformity evidence for high-voltage safety under UN ECE R100, FMVSS 305, GB/T 18384, and battery safety under GB 38031, commonly conducted by accredited third-party laboratories.
• Diagnostic and OBD development: Validating that all injected faults set the correct DTCs, freeze frames, and warning strategies, improving workshop diagnostics and reducing warranty costs.
• Battery safety assessment: Confirming that BMS protection functions—insulation monitoring, overcharge protection, over-discharge protection, and temperature protection—operate correctly under fault conditions before dangerous states are reached.
• Charging system safety: Verifying safe shutdown of AC and DC charging sessions under control pilot faults, communication interruption, grounding faults, and grid voltage anomalies.
• Cybersecurity robustness testing: Evaluating controller behavior under anomalous or manipulated messages as part of ISO/SAE 21434 validation activities.
• Reliability growth and design improvement: Identifying weak points in protection circuits, software degradation strategies, and fail-safe logic early in development to reduce field failures and recalls.

FAQ

What is fault simulation testing for new energy vehicles?

It is a laboratory validation method in which electrical, signal, communication, or thermal faults are deliberately injected into vehicle systems—such as battery packs, inverters, or control units—to verify that the system detects the fault, responds correctly, and reaches a safe state without hazards such as fire, electric shock, or loss of vehicle control.

Which standards govern this type of testing?

Key references include ISO 26262 for functional safety, ISO 6469 and GB/T 18384 for electrically propelled vehicle safety, GB 38031 and IEC 62660 for battery safety, UN ECE R100 and FMVSS 305 for market-specific requirements, ISO 11898 for CAN communication robustness, ISO/SAE 21434 for cybersecurity, and IEC 60068 for environmental conditioning.

Is fault simulation testing destructive?

Most fault injection tests are non-destructive because faults are applied under controlled conditions with protective limits and are removed once the system response is recorded. However, certain worst-case tests—such as insulation breakdown or short circuit tests on battery components—may be destructive and are conducted in dedicated safety enclosures with remote monitoring and fire suppression.

What is the difference between HIL testing and physical fault injection?

HIL testing injects faults into simulated sensor and communication signals while the real controller interacts with a virtual vehicle, making it safe, fast, and repeatable for software validation. Physical fault injection applies real electrical faults—such as short circuits or open circuits—to actual hardware and harnesses, confirming the behavior of the complete electrical path including connectors, contactors, and wiring.

How long does a typical fault simulation program take?

Duration depends on scope. A single component fault matrix may be completed within a few weeks, while a full functional safety validation campaign covering battery, drive, charging, and multiple controllers typically spans several months, including test specification, execution, and reporting by accredited third-party laboratories or in-house test teams.

Why is fault simulation testing especially important for new energy vehicles?

NEVs introduce high-voltage architectures, large-capacity batteries, and complex power electronics whose failure modes can lead directly to severe hazards such as thermal runaway or electric shock. Fault simulation is the only practical way to systematically prove that safety mechanisms work across thousands of potential fault combinations before vehicles reach the road.