Vehicle Engineering Glossary (A–Z)
A comprehensive reference for automotive, EV, hybrid, heavy‑duty, off‑highway, marine, rail, and aerospace engineers.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Formulas
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A
ABS (Anti‑Lock Braking System)
Safety system that prevents wheel lockup during hard braking by modulating brake pressure, improving steering control and stability.
A/C Compressor (Air Conditioning Compressor)
Engine‑ or motor‑driven pump that compresses refrigerant in the vehicle’s climate control system.
Accelerator Pedal Position Sensor (APPS)
Electronic sensor that converts driver pedal input into an electrical signal used by the engine or motor control unit.
Acceleration
Rate of change of velocity with respect to time; fundamental in performance, drivability, and vehicle dynamics analysis.
Accuracy (Measurement)
How close a measured value is to the true value; critical in calibration, emissions, and powertrain testing.
A/D Converter (Analog‑to‑Digital Converter)
Device that converts analog sensor signals (voltage, current) into digital data for ECUs and data acquisition systems.
Active Aerodynamics
Body components that adjust shape or position (e.g., spoilers, grille shutters) to optimize drag, cooling, or downforce.
Active Suspension
Suspension system using actuators, valves, and control algorithms to adapt damping and ride height in real time.
ADAS (Advanced Driver Assistance Systems)
Electronic systems such as lane‑keeping assist, adaptive cruise control, and automatic emergency braking that assist the driver and enhance safety.
Additive Manufacturing (3D Printing)
Layer‑by‑layer manufacturing process used for rapid prototyping and lightweighting components.
ADX
A&D’s portable customizable Portable Real-Time Simulation & Control System.
Aftertreatment System
Exhaust system components (DOC, DPF, SCR, TWC, EGR) used to reduce regulated emissions such as NOx, CO, HC, and particulates.
AGM Battery (Absorbent Glass Mat Battery)
Advanced lead‑acid battery design using glass fiber mats to absorb electrolyte, common in start‑stop and auxiliary power systems.
Air Filter (Engine Air Filter)
Component that removes dust and particulates from intake air to protect the engine and sensors.
Air–Fuel Ratio (AFR)
Mass ratio of air to fuel supplied to an engine; a key parameter for combustion, power, efficiency, and emissions.
Air Spring (Air Suspension)
Suspension component using compressed air in flexible bellows instead of metal coil or leaf springs.
Alternator
Electrical generator driven by the engine that produces electricity to charge the battery and power electrical loads.
Amplitude (Signal)
Peak value of a waveform (e.g., vibration, pressure, noise); used in NVH and structural analysis.
Anode (Battery)
Negative electrode in a battery during discharge; commonly graphite or lithium‑titanate in lithium‑ion cells.
ASAM (Association for Standardization of Automation and Measuring Systems)
Industry group defining standards for measurement, calibration, and diagnostics (e.g., ASAM MCD‑2, MDF, ODS).
Aspect Ratio (Tire)
Ratio of tire sidewall height to its section width, expressed as a percentage (e.g., 225/45 R17).
Axle
Shaft or assembly that supports vehicle weight and transmits driving or braking torque to the wheels.
B
Back EMF (Back Electromotive Force)
Voltage induced in an electric motor that opposes the applied voltage, affecting torque and speed characteristics.
Backpressure (Exhaust Backpressure)
Resistance to exhaust gas flow, often across catalysts, filters, and silencers; impacts engine performance and emissions.
Ball Joint
Spherical bearing allowing multi‑axis articulation between control arms and steering knuckles in the suspension.
Balancing Machine
Equipment used to measure and correct imbalance in rotating components like crankshafts, driveshafts, and rotors.
Battery Cell
Smallest electrochemical energy storage unit, combined into modules and packs in EVs and hybrid vehicles.
Battery Cooling Plate
Heat exchanger integrated into battery packs to maintain cell temperature within safe limits.
Battery Cycler
Programmable instrument used to charge and discharge batteries under controlled profiles; often integrated into test automation with A&D iTest and LabWorX.
Battery Management System (BMS)
Control and monitoring system that protects cells, manages state of charge (SOC), state of health (SOH), balancing, and thermal limits.
Battery Module
Assembly of multiple cells with mechanical housing, interconnects, and sometimes electronics and cooling systems.
Battery Pack
Complete battery assembly including modules, cooling system, contactors, fuses, and BMS; primary energy source in EVs and plug‑in hybrids.
Beam Axle
Rigid axle connecting left and right wheels; used in many trucks, SUVs, and off‑highway vehicles.
Bearing
Mechanical element that reduces friction between moving parts, such as crankshaft main bearings and wheel hub bearings.
BEX‑1000ft
A&D Technology’s FTIR equipment for emissions measurement testing.
Blow‑By Gas
Combustion gases leaking past piston rings into the crankcase; must be managed by crankcase ventilation systems.
Boost Pressure
Intake air pressure above atmospheric provided by a turbocharger or supercharger to increase engine power.
Brake Caliper
Hydraulic component that squeezes brake pads against the rotor to generate braking torque.
Brake Disc (Rotor)
Rotating disc clamped by brake pads in disc brake systems.
Brake Pad
Friction material pressed against the rotor to slow or stop the vehicle.
Brake Fade
Loss of braking performance due to overheating of friction surfaces or brake fluid.
Brake‑Specific Fuel Consumption (BSFC)
Fuel consumption per unit power output, typically expressed in g/kWh; key indicator of engine efficiency in dynamometer testing.
Brushless DC Motor (BLDC)
High‑efficiency electric motor with electronic commutation, widely used in EV traction and accessories.
Busbar (Battery Busbar)
High‑current conductor connecting battery cells or modules within a pack.
C
CAD (Computer‑Aided Design)
Software tools (e.g., CATIA, SolidWorks) used to design and model vehicle components and assemblies.
CAN (Controller Area Network)
Robust vehicle bus standard for ECU communication; essential in powertrain, battery, and chassis integration.
CAN FD (CAN with Flexible Data‑Rate)
Enhanced CAN protocol with higher data throughput and larger payloads for modern ECUs.
Camber Angle
Tilt of a wheel relative to vertical when viewed from the front, affecting tire contact and handling.
Camshaft
Rotating shaft with lobes that open and close engine valves in synchronization with the crankshaft.
CANape / CANoe / CANalyzer
Common tools for ECU development, calibration, and network analysis that can be integrated with test systems.
Carburetor
Legacy fuel metering device that mixes air and fuel using pressure differentials; largely replaced by fuel injection.
CARB (California Air Resources Board)
Regulatory agency setting emissions and air‑quality standards; often more stringent than federal rules.
Caster Angle
Angle of steering axis in the side view; influences straight‑line stability and steering feel.
Catalytic Converter
Exhaust component using precious metal catalysts to convert CO, HC, and NOx into less harmful gases.
Cell Balancing (Battery)
Process of equalizing individual cell voltages to maximize pack capacity and longevity.
CFD (Computational Fluid Dynamics)
Numerical simulation method used to analyze airflow, cooling, combustion, and aerodynamics.
Chassis
Structural framework including frame or unibody, suspension, steering, and brakes that supports the vehicle body and powertrain.
Chassis Dynamometer
Test stand that supports a complete vehicle on rollers, enabling controlled testing of power, emissions, and energy consumption.
Charge Air Cooler (Intercooler)
Heat exchanger that cools compressed intake air from a turbocharger or supercharger.
Charge Rate (C‑Rate)
Battery charge/discharge current expressed relative to rated capacity (e.g., 1C = full charge in one hour).
Closed‑Loop Control
Control strategy that adjusts actuators based on feedback from sensors (e.g., lambda control, speed control on a dyno).
Coefficient of Drag (Cd)
Dimensionless parameter quantifying aerodynamic drag; lower values indicate more streamlined designs.
Combustion Analysis
High‑speed acquisition and analysis of in‑cylinder pressure and related signals used to optimize efficiency, knock margin, and emissions; often integrated into automated dyno systems with iTest.
Compliance (Suspension)
Elastic deformation of suspension components under load that affects ride, handling, and alignment.
Connecting Rod (Con Rod)
Component linking piston to crankshaft, converting reciprocating motion into rotation.
Control Arm (A‑Arm)
Suspension link connecting the chassis to the steering knuckle or axle, guiding wheel motion.
Control Room Automation
Centralized control of multiple test stands, safety systems, and data flows using platforms such as A&D iTest and LabWorX.
Crankcase
Lower portion of the engine block housing the crankshaft and oil.
Crankshaft
Main rotating shaft driven by pistons that delivers torque to the transmission or drivetrain.
Crewed Test Cell Operation
Traditional test methodology where operators run tests from a control room; increasingly automated via test scripts and platforms like iTest and LabWorX.
D
DA (Data Acquisition)
See Data Acquisition.
Data Acquisition (DAQ)
System for measuring and recording physical variables such as pressure, temperature, torque, speed, voltage, and current. A&D’s, Phoenix platforms provide high‑speed, synchronized DAQ for test stands.
Data Logger
Device or software system used to record signals over time that can provide centralized data management and archiving across test cells.
DC Fast Charger
High‑power charging station that supplies DC energy directly to EV batteries, enabling rapid charging.
Deflection
Displacement of a component under load; important in suspension and structural analysis.
Diesel Exhaust Fluid (DEF)
Aqueous urea solution used inSelective Catalytic Reduction (SCR) systems to reduce NOx emissions from diesel engines.
Diesel Particulate Filter (DPF)
Porous filter in the exhaust system that traps soot particles and periodically regenerates via oxidation.
Differential
Gear assembly that splits engine torque between left and right wheels while allowing speed differences during cornering.
Disc Brake
Braking system using calipers and pads to clamp onto a rotating disc (rotor).
Displacement (Engine)
Total swept volume of all cylinders, commonly given in liters or cubic centimeters (cc).
DOHC (Dual Overhead Camshaft)
Valve train configuration with separate camshafts for intake and exhaust valves.
Drag Coefficient
See Coefficient of Drag.
Drive Cycle
- Emissions certification
- Benchmarking across platforms
- Battery and EV range analysis
- Calibration and controls development
- Aftertreatment evaluation (SCR, DPF regen, NOx conversion, etc.)
Driveline / Drivetrain
Components transmitting power from the engine or motor to the wheels (transmission, driveshafts, differential, axles).
DTC (Diagnostic Trouble Code)
Fault code stored by ECUs when a malfunction is detected; accessed via OBD tools.
Dynamometer (Dyno)
Test machine that measures torque and speed to determine power and efficiency of engines, motors, transmissions, or full vehicles. A&D specializes in dyno automation and integration with iTest and LabWorX.
E
ECM (Engine Control Module)
Electronic unit managing fuel, air, spark, and emissions for internal combustion engines.
ECU (Electronic Control Unit)
Generic term for any embedded controller in the vehicle (engine, transmission, BMS, ABS, ADAS).
EGR (Exhaust Gas Recirculation)
System that routes a portion of exhaust gas back into the intake to reduce NOx emissions.
Electric Drive Unit (EDU)
Integrated assembly combining electric motor, inverter, and sometimes transmission gearing.
Electric Motor
Machine that converts electrical energy into mechanical power; types include induction, permanent magnet synchronous, andBrushless Direct Current (BLDC).
Electrical Harness (Wiring Harness)
Bundled set of wires, connectors, and protective coverings supplying power and signals throughout the vehicle.
Electrolyte (Battery)
Ion‑conducting medium in a cell enabling charge transfer between anode and cathode.
Electron Gun
A&D designs and manufactures electron gun assemblies and high‑voltage power supplies that serve as the heart of modern Scanning Electron Microscopes (SEMs). These SEM systems are essential for inspecting, measuring, and characterizing the wafers that drive today’s semiconductor devices.
EMC (Electromagnetic Compatibility)
Ability of electronic systems to operate properly in their electromagnetic environment without causing or suffering interference.
Emission Control System
Combination of hardware and control strategies that manage exhaust pollutants; includes EGR, catalysts, DPF, SCR, and control algorithms.
Emissions Bench
Instrumentation suite for measuring tailpipe gases (CO, CO₂, NOx, HC, O₂, PM) during engine and vehicle testing.
End‑of‑Line (EOL) Testing
Final functional testing in production to validate components or vehicles before shipment.
Energy Density (Battery)
Amount of energy stored per unit mass (Wh/kg) or volume (Wh/L); key EV performance metric.
Engine Block
Main structure of an engine housing cylinders, coolant jackets, and crankcase.
Engine Control Unit (ECU)
Specialized ECU that manages engine operation, sometimes integrated with transmission control for powertrain optimization.
Engine Mapping
Process of systematically varying and measuring engine parameters across speed and load to create control maps (spark, fuel, boost, etc.).
Engine Test Cell
Dedicated room with dynamometer, emissions equipment, and safety systems for engine testing.
EPA (Environmental Protection Agency)
U.S. federal agency that sets emissions and fuel economy regulations for vehicles and engines.
Exhaust Manifold
Component collecting exhaust gases from cylinders and directing them to the catalyst and exhaust system.
F
FCEV (Fuel Cell Electric Vehicle)
Vehicle powered by a hydrogen fuel cell stack generating electricity for drive motors.
FEA (Finite Element Analysis)
Numerical simulation technique for analyzing structural stress, strain, and deformation.
Fender
Body panel covering the wheel to contain road debris and spray.
Friction Brake
Conventional brake system where kinetic energy is dissipated as heat in pads and rotors or drums.
Friction Coefficient
Ratio describing the resistance to sliding motion between two surfaces; critical in tire, brake, and bearing design.
FMEA (Failure Modes and Effects Analysis)
Structured process to identify potential failure modes, assess risk, and prioritize mitigations.
FMEP (Friction Mean Effective Pressure)
Thermodynamic measure of internal engine friction losses.
Fuel Injector
Precision valve that sprays atomized fuel into the combustion chamber or intake port.
Fuel Pump
Device that delivers fuel from the tank to the engine under controlled pressure.
Fuel Rail
High‑pressure fuel distribution manifold supplying injectors in modern engines.
Full Hybrid
Hybrid vehicle capable of running on engine only, motor only, or a combination of both.
G
Gasoline Direct Injection (GDI)
Fuel injection technology where gasoline is injected directly into the combustion chamber at high pressure.
Gauge Factor (Strain Gauge)
Ratio of relative resistance change to strain, used in load cells and strain measurement.
Gear Ratio
Ratio between input and output shafts in a gear set, determining torque multiplication and speed reduction.
Gearbox (Transmission)
Assembly of gears and clutches that adjusts torque and vehicle speed relative to engine or motor speed.
Gen‑Set (Generator Set)
Engine‑driven generator used in hybrid powertrains, backup power, and off‑highway equipment.
GKN Joint / CV Joint
Constant velocity joint allowing power transmission through variable angles in drive shafts.
Ground Clearance
Vertical distance between the lowest vehicle component and the ground.
Ground Vehicle Simulation (GVS)
Real‑time modeling of vehicle powertrain and dynamics for HIL testing of ECUs using platforms like Helios HILS.
H
Hall‑Effect Sensor
Sensor using the Hall effect to measure magnetic fields, commonly used for speed and position sensing.
Harness (Wiring Harness)
See Electrical Harness.
Hardware‑in‑the‑Loop (HIL)
Real‑time simulation framework connecting physical ECUs to virtual plants (engine, motor, battery, vehicle). A&D’s HILS platforms support powertrain, battery, motor, ADAS, and thermal component simulation.
HCCI (Homogeneous Charge Compression Ignition)
Advanced combustion strategy where a premixed charge auto‑ignites under compression, targeting high efficiency and low NOx.
Head Gasket
Seal between cylinder head and engine block maintaining compression and preventing leaks.
Header (Exhaust Header)
Performance‑oriented exhaust manifold with tuned primary tubes for improved scavenging.
Heat Exchanger
Device that transfers heat between fluids (coolant, oil, air, refrigerant) without mixing them.
Heat Flux
Rate of heat transfer per unit area; often measured in battery and power electronics testing.
Helios HILS
A&D Technology’s HIL platform designed for validated, real‑time simulation of engines, motors, batteries, and full powertrains.
Horsepower (hp)
Horsepower is a measure of power—how quickly work is done. In vehicles, it describes how fast an engine or motor can deliver energy to move a load, accelerate a vehicle, or sustain speed.
Originally defined by James Watt, 1 horsepower = 550 lb‑ft per second, or 746 watts. While the origin is historical, horsepower remains a practical way to compare power output across propulsion technologies.
Typical Horsepower Ranges (approximate):
– Passenger cars: 100–300 HP
– Performance & luxury vehicles: 300–700+ HP
– Light trucks & SUVs: 250–450 HP
– Heavy‑duty diesel engines: 400–700+ HP
– Electric motors (road vehicles): 150–600+ HP equivalent
– Off‑highway, marine, rail, and aerospace systems: ranges vary widely based on duty cycle and application
How Horsepower is Calculated:
Horsepower is derived from torque and rotational speed:
– HP = (Torque × RPM) / 5252
– Torque is the twisting force (lb‑ft)
– RPM is rotational speed
– 5252 is a constant that aligns the units
This relationship is why dyno testing always measures torque first—horsepower is calculated.
How Horsepower is Used in Engineering & Testing:
– Performance validation: Confirms engines, motors, and powertrains meet design targets
– Comparison metric: Enables benchmarking across ICE, hybrid, and electric platforms
– Calibration & optimization: Helps engineers tune for efficiency, durability, and drivability
– Regulatory & compliance testing: Supports emissions, efficiency, and certification programs
– System modeling & simulation: Feeds accurate power data into virtual development workflows
Hub (Wheel Hub)
Central part of the wheel assembly that houses bearings and mounts to the suspension and wheel.
Hybrid Electric Vehicle (HEV)
Vehicle combining an internal combustion engine with one or more electric machines and a hybrid battery.
I
iTest
A&D Technology’s customizable test automation and control software, used for engine, motor, battery, and powertrain test stands, integrating dynos, ECUs, emissions benches, and safety systems.
ICE (Internal Combustion Engine)
Engine that burns fuel and air inside cylinders to produce mechanical work.
Idle Speed Control
Closed‑loop control of engine speed at idle using throttle, ignition, or fuel adjustments.
Ignition Coil
Device that steps up battery voltage to high voltage required to fire spark plugs.
Ignition Timing
Crank angle at which the spark plug fires; critical for power, efficiency, and knock margin.
IMU (Inertial Measurement Unit)
Instrument measuring accelerations and angular rates along multiple axes; used in vehicle dynamics and ADAS.
Induction Motor
AC motor that uses electromagnetic induction; widely used in some EV platforms.
Inertia (Rotational Inertia)
Resistance of a rotating object to changes in angular speed; important in dyno and driveline modeling.
Intake Manifold
Component distributing air (or air‑fuel mixture) to individual cylinders.
ISO (International Organization for Standardization)
Body responsible for international standards.
Here are some of the most common ISO standards in vehicle engineering:
- ISO 26262 – Functional Safety for Road Vehicles
Defines the lifecycle processes required to ensure functional safety of electrical and electronic (E/E) systems in vehicles. Central to ADAS, EV propulsion, and autonomous development. - ISO 21434 – Road Vehicles Cybersecurity Engineering Establishes cybersecurity risk‑management requirements for connected and automated vehicles throughout design, development, production, and operation.
- ISO 16750 – Environmental Conditions & Testing for Electrical/Electronic Equipment Covers environmental durability tests—temperature, vibration, shock, humidity, chemical exposure—ensuring onboard electronics survive real‑world conditions.
- ISO 6469 – Safety Specifications for Electrically Propelled Road Vehicles Provides safety requirements for the functional, operational, and energy-storage aspects of EVs, including batteries and high‑voltage systems.
- ISO 11898 – CAN Communications (Controller Area Network) Defines the data‑link and physical layer for CAN networks, the backbone of automotive communication for powertrain, chassis, and body controllers.
- ISO 14229 – Unified Diagnostic Services (UDS) Specifies diagnostic communication protocols between vehicle ECUs and test equipment, essential for calibration, flashing, and service diagnostics.
- ISO 9001 – Quality Management Systems A globally adopted standard ensuring consistent quality management processes across automotive product development, production, and testing.
- ISO 14001 – Environmental Management Systems Guides organizations in establishing systems to reduce environmental impact—important for proving sustainability across vehicle design and test operations.
- ISO 23273 – Hydrogen Fuel Cell Vehicle Safety Defines safety requirements for hydrogen storage, handling, and fuel cell systems in road vehicles.
- ISO 8855 – Vehicle Dynamics and Road-Holding Terminology Provides standard definitions for vehicle dynamics parameters—critical for consistency in modeling, simulation, and testing of chassis and ADAS systems.
J
Jerk (Vehicle Dynamics)
Rate of change of acceleration; impacts perceived ride comfort and control strategy tuning.
Journal Bearing
Type of bearing supporting a shaft with a thin fluid film, common in crankshafts and turbochargers.
Joule Heating (I²R Losses)
Heat generated in conductors and resistive elements due to electric current; major loss mechanism in wiring and busbars.
Jounce and Rebound
Upward (jounce) and downward (rebound) movements of the wheel and suspension relative to the body.
K
Kammback / Kamm Tail
Aerodynamic design where rear bodywork is abruptly cut off to reduce drag without a full taper.
KERS (Kinetic Energy Recovery System)
System that recovers braking energy and stores it (mechanically or electrically) for later use; used in racing and hybrid systems.
Key‑On / Key‑Off Cycle
Repetition of ignition cycles used in durability and diagnostic testing.
Knock (Engine Knock / Detonation)
Abnormal combustion characterized by pressure oscillations; controlled via knock sensors and spark/fuel strategies.
Knock Sensor
Piezoelectric sensor that detects engine knock vibrations for real‑time spark control.
KPI (Key Performance Indicator)
Metric used to track test lab, vehicle, or program performance; LabWorX enables KPI dashboards and reporting.
L
LabWorX
A&D Technology’s lab management platform to manage test lab assets and processes.
Lambda (λ)
Air–fuel equivalence ratio; λ = 1 indicates stoichiometric mixture, λ < 1 rich, λ > 1 lean.
Lambda Sensor (Oxygen Sensor)
Sensor measuring exhaust oxygen content, enabling closed‑loop fuel control.
Lane‑Keeping Assist (LKA)
ADAS feature that helps keep the vehicle centered within its lane.
Lap Joint / Weld Joint
Common joint types used in vehicle body and frame manufacturing.
Launch Control
Performance feature optimizing traction and torque at vehicle launch.
Leaf Spring
Suspension element consisting of stacked metal strips; common in trucks and trailers.
Lithium‑Ion Battery
Rechargeable battery chemistry widely used in EVs and energy storage systems.
Load Cell
Force transducer used for measuring weight, tension, or torque in test rigs and dynos.
Longitudinal Dynamics
Vehicle motion along its travel direction including acceleration, braking, and gradeability.
Low‑Voltage System (12 V / 24 V)
Conventional electrical architecture powering accessories, lighting, and control modules.
M
MacPherson Strut
Space‑efficient front suspension combining a shock absorber and a coil spring.
Manifold Absolute Pressure (MAP) Sensor
Sensor measuring absolute pressure in the intake manifold, used for load calculation.
Mass Air Flow (MAF) Sensor
Sensor measuring incoming air mass for fuel control.
Material Testing
Mean Effective Pressure (MEP)
Hypothetical pressure that, if applied uniformly to the piston, would produce the observed power output.
Motor Controller / Inverter
Power electronics that convert DC battery voltage into AC waveforms for traction motors.
Motor Efficiency Map
2D or 3D map showing motor efficiency as a function of torque and speed.
MPPT (Maximum Power Point Tracking)
Control strategy used in renewable systems and sometimes integrated with hybrid energy flows to maximize power extraction.
Multibody Dynamics
Simulation methodology modeling vehicle structures as interconnected rigid or flexible bodies.
N
NEDC / WLTP / EPA Cycles
Standardized drive cycles used for emissions and fuel/energy consumption measurements.
Neutral Gear
Transmission position that decouples engine/motor torque from the wheels.
Noise, Vibration, and Harshness (NVH)
Engineering domain focused on controlling acoustic noise, vibration, and ride harshness.
Nominal Capacity (Battery)
Rated capacity of a cell or pack, usually in ampere‑hours, under specified conditions.
NOx (Nitrogen Oxides)
Group of pollutants formed during high‑temperature combustion, regulated by emissions standards.
O
OBD (On‑Board Diagnostics)
Vehicle self‑diagnostic and reporting system; OBD‑II is the standardized interface for light‑duty vehicles.
OBD-II
If you’ve ever seen a “check engine” light pop on, you’ve experienced OBD-II in action—but what exactly is it?
OBD-II (On-Board Diagnostics, second generation) is a standardized system built into modern vehicles that continuously monitors engine performance, emissions systems, and other critical components. It gives technicians—and increasingly engineers—access to real-time vehicle health data through a common interface.
What does OBD-II actually do?
OBD-II systems monitor sensors and subsystems across the vehicle. When something falls outside expected thresholds, the system logs a Diagnostic Trouble Code (DTC) and may trigger a dashboard warning light. These codes help pinpoint where issues may exist.
Examples of common OBD-II codes:
- P0300: Random/multiple cylinder misfire detected
- P0171: System too lean (bank 1)
- P0420: Catalyst system efficiency below threshold
- P0455: Large evaporative emissions leak detected
Each code follows a standardized structure, with the first letter indicating the system:
- P = Powertrain
- B = Body
- C = Chassis
- U = Network/communication
Who defines these codes?
OBD-II standards—including many generic DTCs—are defined by organizations like the SAE (Society of Automotive Engineers) and mandated by regulatory agencies like the EPA and CARB to ensure compliance with emissions requirements. Manufacturers can also add their own proprietary codes for more specific diagnostics.
How are OBD-II codes read?
Technicians (and even car owners) can access codes through the standardized OBD-II port, typically located under the dashboard. Using scan tools—from handheld readers to advanced data acquisition systems—users can retrieve codes, clear faults, and monitor live data streams.
Why does OBD-II matter to engineers?
Beyond repair diagnostics, OBD-II plays a critical role in vehicle development, calibration, and validation. It provides a consistent framework for capturing performance data, validating emissions compliance, and troubleshooting issues during testing—especially when integrated into advanced data acquisition and simulation systems.
Open‑Loop Control
Control method that does not use feedback from the process variable (e.g., open‑loop fuel enrichment maps).
Orion
A&D’s automated calibration software.
Orthogonal Design Experiment
Statistically structured test plan used in calibration and design of experiments (DOE).
Oversteer
Handling characteristic where the rear tires lose grip before the front, causing the vehicle to turn more than commanded.
Overvoltage / Undervoltage
Battery or power system conditions where voltage exceeds or drops below safe limits; monitored by BMS and protective devices.
P
Paddle Shifter
Steering‑wheel‑mounted controls allowing manual command of gear changes in automatic or dual‑clutch transmissions.
Park Lock / Parking Pawl
Mechanical device that locks transmission output to prevent vehicle movement in park.
PCU (Powertrain Control Unit)
Integrated controller managing multiple powertrain functions including engine, transmission, hybrid modes, and sometimes BMS.
Permanent Magnet Synchronous Motor (PMSM)
High‑efficiency traction motor using permanent magnets on the rotor.
Phoenix
A&D’s Combustion Analysis System for Powertrain Development, Engine Calibration, Post-Production, & Knock Evaluation.
PID Control (Proportional‑Integral‑Derivative)
Common feedback control algorithm used for engine idle, speed control on dynos, thermal management, and more.
Piston
Cylindrical component reciprocating inside the cylinder; transmits combustion forces to the connecting rod.
Pitot Tube
Device measuring fluid flow velocity via pressure differential; used in aerodynamics and wind tunnel testing.
Planetary Gear Set
Compact gear arrangement used in automatic and hybrid transmissions to provide multiple gear ratios.
PLC (Programmable Logic Controller)
PLC is a ruggedized industrial control computer used to automate mechanical and electrical processes. In vehicle testing, PLCs execute real‑time control logic to manage equipment such as dynamometers, actuators, safety systems, and facility infrastructure.
What is a PLC used for in vehicle testing?
-
Test Cell Automation
Controls dyno operations, throttle/brake actuation, cooling systems, and test sequences. -
Safety Interlocks & Emergency Controls
Monitors conditions (overspeed, overtemperature, door interlocks) and executes fail-safe shutdowns. -
Facility Control Integration
Interfaces with HVAC, fuel systems, emissions handling, and power distribution. -
Real-Time Deterministic Control
Executes logic with precise timing—essential for synchronized testing of engines, motors, batteries, and full powertrains. -
I/O Management
Handles digital and analog signals from sensors, relays, switches, and field devices.
Plug‑In Hybrid Electric Vehicle (PHEV)
Hybrid vehicle with a larger battery that can be charged from the grid to provide extended electric‑only range.
Power Density
Power output per unit mass or volume, important for motors, inverters, and engines.
Power Electronics
Electronics (inverters, DC‑DC converters, chargers) that manage and convert electrical power in EVs and hybrids.
Power Steering
Assist system using hydraulic or electric power to reduce driver steering effort.
Powertrain
Entire set of components that generate and transmit power to the wheels (engine or motor, transmission, differential, axles).
Press Hardening
Hot forming process used to produce ultra‑high‑strength steel components for safety structures.
Prototype
Early version of a component or system used for development, testing, and validation.
Q
Quasi‑Static Test
Slowly varying test used to characterize structural performance or component behavior (e.g., crush tests).
Quick‑Ratio Steering
Steering system with a higher steering wheel angle to wheel angle conversion, providing a more responsive feel.
Quiescent Current
Current drawn by an ECU or system in standby or key‑off condition.
R
Rack‑and‑Pinion Steering
Steering mechanism that converts rotation of the steering wheel into linear motion of the steering rack.
Radial Tire
Tire construction where plies run radially from bead to bead, improving performance and durability.
Range (EV Driving Range)
Maximum distance an EV can travel on a full charge under specified conditions.
Range Extender
Auxiliary power unit (often a small ICE) used to recharge batteries or supply power in extended‑range EVs.
Rate of Charge / Discharge
See C‑Rate.
Rear Axle
Assembly including differential, driveshafts, and wheel end components at the rear of the vehicle.
Recirculating Ball Steering
Steering mechanism commonly used in heavy‑duty vehicles and trucks.
Regen (Regenerative Braking)
Process by which electric motors act as generators during braking, converting kinetic energy into stored electrical energy.
Reinforced Body Structure
Use of high‑strength materials and geometries to improve crashworthiness.
Reliability Testing
Testing strategy aimed at assessing component or system durability under extended conditions and duty cycles.
RDE (Real Driving Emissions)
On‑road emissions testing using portable analyzers rather than only laboratory cycles.
Redline
Maximum allowable engine speed as indicated on the tachometer.
Ride Height Sensor
Sensor measuring the distance between body and axle or wheel, used in active suspension and headlamp leveling systems.
Roll Center
Theoretical point around which the body rolls in cornering; influences handling behavior.
Roll Cage
Safety structure used in racing, off‑road, and extreme duty vehicles to protect occupants.
Rotary Encoder
Sensor measuring angular position or speed of a rotating shaft.
S
Safety Belt (A&D Safety Belt Software Maintenance Plan)
A subscription service providing access to regular software upgrades with the latest functionality and enhancements. For a minimal fixed yearly cost, updates and patches are made available via secure download from the Customer Portal. This ensures your system stays current with the latest operating system and minimizes both potential security threats and the expensive downtime required for upgrades.
SAE (Society of Automotive Engineers / SAE International)
Professional organization that develops many vehicle standards and test procedures.
SCR (Selective Catalytic Reduction)
Aftertreatment system that uses DEF to convert NOx into nitrogen and water in diesel exhaust.
Selene
A&D’s compact, low cost, prototyping tool.
Sensor Fusion
Combining data from multiple sensors (radar, camera, lidar, GPS, IMU) for ADAS and automated driving.
Side‑Impact Beam
Structural component in doors and body to improve crash performance in side collisions.
Slip Ratio (Tire)
Difference between tire circumferential speed and vehicle speed, normalized by vehicle speed; key parameter in traction and ABS control.
SOC (State of Charge)
Estimated percentage of remaining battery capacity relative to its usable range.
SOH (State of Health)
Indicator of battery aging and capacity fade relative to its original condition.
SOE (State of Energy)
Measure of remaining energy content in a battery pack.
Spark Plug
Device that initiates combustion in spark‑ignition engines by generating an electric spark.
Speed Sensor
Sensor measuring rotational speed of engine, motor, wheel, or shaft.
Stator
Stationary part of electric motor or generator containing windings.
Strain
Deformation of a material relative to its original length; used in structural testing with strain gauges.
Stress
Internal force per unit area in a material; fundamental in structural analysis.
Suspension
System of springs, dampers, and links connecting the wheels to the vehicle body, controlling ride and handling.
Swirl and Tumble
Air motion patterns in combustion chambers that enhance mixing and combustion.
T
Tachometer
Instrument indicating rotational speed (RPM) of an engine or motor.
Telematics
Communication technologies that transmit vehicle data to external systems for diagnostics, fleet management, or analytics.
Thermal Management System
Integrated system controlling temperatures of engine, battery, motor, inverter, cabin, and power electronics.
Thermal Runaway (Battery)
Uncontrolled exothermic reaction in a cell leading to rapid temperature rise and potential failure; critical focus of safety testing.
Throttle Body
Valve controlling airflow into the engine intake manifold.
Tie‑Rod
Steering component connecting the steering rack to the wheel knuckle.
Torque
Rotational force applied to a shaft, described as the product of force and distance.
Torque Converter
Hydrodynamic device in automatic transmissions that multiplies torque and allows slip between engine and transmission.
Torque Ripple
Fluctuation in torque output of electric machines; important for NVH and drivability.
Total Harmonic Distortion (THD)
Measure of waveform distortion in electrical systems, relevant to inverters and motor drive quality.
Track Width
Distance between the centers of left and right wheels on the same axle.
Traction Control System (TCS)
System that modulates engine torque and braking to maintain traction and prevent wheel spin.
Traction Inverter
High‑power inverter controlling a traction motor in an EV or hybrid.
Transfer Case
Gearbox used in four‑wheel‑drive and all‑wheel‑drive vehicles to distribute torque between front and rear axles.
Transient Test
Test where speed, load, or other variables change dynamically over time, as in real drive cycles.
Turbocharger
Exhaust‑driven compressor that increases intake air mass and engine output.
U
UAV: Unmanned Aerial Vehicle. UAV stands for Unmanned Aerial Vehicle. A UAV is an aircraft that operates without a pilot onboard, flying remotely or autonomously. While often called “drones,” the term UAV is used in engineering because it represents the entire vehicle system—propulsion, batteries, controls, and structure.
How A&D supports UAV R&D testing:
– Electric motor and propulsion testing with dynamometer-based systems
– Battery and power electronics validation for performance, safety, and lifecycle
– Hardware-in-the-loop (HIL) testing to de-risk controls and autonomy
– Automated data acquisition and analysis across electrical and mechanical systems
UDS (Unified Diagnostic Services)
ISO‑standardized diagnostic protocol used over CAN or Ethernet for ECU diagnostics and flashing.
Unibody (Unitized Body)
Construction method where the body structure and frame are integrated into a single unit.
Understeer
Handling behavior where the vehicle turns less than commanded because the front tires lose grip first.
Universal Joint (U‑Joint)
Flexible coupling that connects shafts at angles, transmitting torque while accommodating misalignment.
Unsprung Mass
Masses not supported by the suspension (wheels, hubs, portions of suspension arms); lower unsprung mass improves ride and handling.
Upright (Steering Knuckle)
Component connecting the suspension arms, hub, and steering linkage.
V
Valence (Battery)
Oxidation state concept relevant to electrode reaction chemistry.
Valve (Engine Valve)
Component controlling the flow of intake air/fuel and exhaust gases into and out of the cylinder.
Valvetrain
System of camshaft, followers, valves, springs, and actuators controlling valve timing and lift.
Vehicle Control Unit (VCU)
Central controller managing vehicle‑level functions, often coordinating motor, engine, BMS, and chassis systems.
Vehicle Dynamics
Study of motions and forces acting on a vehicle including acceleration, handling, stability, and braking.
Vehicle Stability Control (ESC / ESP)
System that applies individual wheel braking and torque modulation to help maintain directional control.
Vibration
Oscillatory motion of components or structures; source of NVH issues.
Volumetric Efficiency (VE)
Ratio of actual mass of air inducted into a cylinder to the theoretical maximum at atmospheric conditions.
Voltage Sag / Swell
Short‑term deviation of voltage from nominal in electrical systems.
VTOL / eVTOL
Vertical take‑off and landing aircraft, increasingly relevant to advanced air mobility engineering.
W
Wastegate
Valve controlling turbocharger boost by bypassing exhaust around the turbine.
Water Pump (Coolant Pump)
Pump circulating coolant through engine, battery, and radiator for thermal management.
Wheel Alignment
Adjustment of toe, camber, and caster to ensure proper tire wear and handling.
Wheel Hub Assembly
Unit including hub, bearings, mounting flange, and sometimes wheel speed sensor.
Wheel Speed Sensor
Sensor used by ABS, traction control, and stability control systems to measure wheel rotational speed.
Wheelbase
Distance between front and rear axle centers; affects stability, ride, and packaging.
Wind Tunnel
Facility that generates controlled airflow over vehicles or models for aerodynamic and thermal testing.
WLTP (Worldwide Harmonized Light Vehicles Test Procedure)
Global standard for emissions and fuel/energy consumption testing.
Work Instruction (Test)
Standardized document describing procedures for running a test, often implemented as automated scripts in iTest or LabWorX.
X
X‑By‑Wire Systems (Steer‑By‑Wire, Brake‑By‑Wire)
Systems where electronic signals, rather than mechanical or hydraulic links, transmit driver commands to actuators.
X‑Axis, Y‑Axis, Z‑Axis
Orthogonal axes used to define vehicle motion and sensor orientation (longitudinal, lateral, vertical).
Y
Yaw Rate
Rate at which a vehicle rotates around its vertical axis; measured by gyroscopes for ESC and ADAS.
Yield Strength
Stress at which a material begins to deform plastically; critical for safety‑critical structural components.
Yoke (Driveshaft Yoke)
Component that connects the driveshaft to the transmission or differential via universal joints.
Z
ZEV (Zero‑Emission Vehicle)
Vehicle that produces no tailpipe emissions; includes battery electric and some fuel cell vehicles.
Zonal Architecture
Emerging electrical/electronic architecture grouping functions by vehicle zones rather than centralized ECUs.
Z‑Value (NVH / Statistical)
Statistical measure used in data analysis and quality assurance.
Z‑Wheel / Z‑Axis Vibration
Vertical vibration component, relevant to ride comfort and durability.
Common Automotive & Vehicle Engineering Formulas
Below are widely used formulas that support engine, powertrain, EV, and vehicle dynamics engineering. All symbols assume SI units unless noted otherwise.
Power, Torque, and Speed
PkW=TNm×ωrad/s1000or using RPM:
Php=Tlb\cdotpft×nRPM5252
TNm=PkW×60 0002π×nRPMT_\text{Nm} = \frac{P_\text{kW} \times 60\,000}{2\pi \times n_\text{RPM}}
Vehicle Dynamics and Braking
Froll=Crr×mg
Grade Force (Climbing a Slope)
Fgrade=mgsin(θ)F_\text{grade} = m g \sin(\theta)Braking Distance (Idealized)
dbrake=v22μgd_\text{brake} = \frac{v^2}{2 \mu g} Lateral Acceleration in a Turn
Engine Performance and Combustion
BSFC=m˙fuelPbrakeVolumetric Efficiency (VE)
ηv=m˙air, actualm˙air, theoretical\eta_v = \frac{\dot{m}_\text{air, actual}}{\dot{m}_\text{air, theoretical}}Air–Fuel Ratio (AFR)
λ=AFRactualAFRstoich
Electrical and EV Systems
P=3×VL×IL×cos(ϕ)P = \sqrt{3} \times V_\text{L} \times I_\text{L} \times \cos(\phi)Battery Energy (Ideal)
E=CAh×Vnom[Wh]E = C_\text{Ah} \times V_\text{nom} \quad [\text{Wh}] State of Charge (SOC)
SOC(t)=SOC(t0)−1Cnom∫t0tI(τ) dτ\text{SOC}(t) = \text{SOC}(t_0) – \frac{1}{C_\text{nom}} \int_{t_0}^{t} I(\tau)\, d\tau Ohm’s Law
V=IRV = I R
Joule Heating (I²R Losses)
Ploss=I2RP_\text{loss} = I^2 R
Thermodynamics and Heat Transfer
pV=nRTpV = nRTHeat Transfer (Conduction)
(Newton’s Law of Cooling)
ηotto=1−1rγ−1\eta_\text{otto} = 1 – \frac{1}{r^{\gamma – 1}} where r is compression ratio and γ is specific heat ratio.
NVH and Structural Mechanics
fn=12πkm Strain
σ=Eε\sigma = E \varepsilon
