Every part, in plain language.
199 components: what each one does, where it sits, the symptoms when it fails and what BMW does differently.
199 parts
Engine internals
Engine block Holds the cylinders and supports the engine’s rotating parts. Cylinder head Closes the cylinders and carries the valves that control breathing. Cylinder-head gasket Seals combustion pressure, oil and coolant between the block and head. Piston Receives combustion force and moves up and down inside a cylinder. Piston rings Seal combustion gas and control the oil film on cylinder walls. Connecting rod Transfers piston force to the crankshaft. Crankshaft Turns the pistons’ back-and-forth motion into rotation. Crankshaft main bearing Supports the crankshaft on a controlled film of oil. Connecting-rod bearing Lets a connecting rod rotate around its crankshaft journal. Camshaft Times the opening and closing of engine valves. Intake valve Opens a passage for fresh air into a cylinder. Exhaust valve Lets burned gas leave the cylinder. Valve spring Returns a valve toward its closed position. Timing chain Keeps crankshaft and camshaft movement synchronized. Timing-chain tensioner Maintains suitable tension in the timing-chain path. Cylinder-head cover Seals the top of the engine around the valve gear. Crankcase ventilation valve Controls how crankcase gas returns to the intake. VANOS cam-timing system Changes when the engine valves open and close. Valvetronic valve-lift system Varies how far the intake valves open to control airflow. Engine mount Holds the engine while isolating vibration from the body. Crankshaft vibration damper Absorbs twisting vibration at the front of the crankshaft. Piston pin Joins the piston to the small end of the connecting rod. Piston cooling jet Sprays oil under the piston crown to carry heat away. Cylinder bore surface Forms the wall the piston and rings slide against. Roller finger follower Transfers cam-lobe motion to the valve. Hydraulic lash adjuster Keeps valve clearance at zero automatically. Crankshaft position sensor Tells the engine computer the exact crank angle and speed. Camshaft position sensor Reports camshaft position so timing can be checked and adjusted. Knock sensor Listens for uncontrolled combustion so timing can back off.
Air & turbo
Engine air filter Removes dust from air before it enters the engine. Air-filter housing Holds the air filter and directs clean air into the intake. Intake manifold Distributes incoming air to the cylinders. Throttle body Uses a movable plate to regulate an intake passage. Turbocharger Uses exhaust energy to push more air into the engine. Turbo wastegate Diverts exhaust around the turbine to help control boost. Turbo diverter valve Relieves compressed intake air when operating conditions call for it. Charge-air cooler Removes heat from compressed intake air. Charge pipe Carries pressurized air from the turbo toward the engine. Air-mass sensor Measures incoming air mass for engine management. Manifold-pressure sensor Measures air pressure in the intake system. Intake resonator Changes the sound waves traveling through the intake. TwinPower Turbo technology family Names a BMW engine-technology package whose hardware varies by engine. Compressor wheel Spins to draw in and compress intake air. Twin-scroll turbine housing Keeps exhaust pulses from different cylinders apart until the turbine.
Fuel & ignition
Fuel tank Stores the fuel carried by a combustion car. In-tank fuel pump Moves fuel from the tank toward the engine. High-pressure fuel pump Raises fuel pressure for direct injection. Fuel rail Distributes pressurized fuel to the injectors. Fuel injector Meters fuel into the intake or combustion chamber. Fuel filter Traps contamination before it reaches sensitive fuel hardware. Fuel-pressure sensor Reports fuel pressure so delivery can be controlled. Spark plug Starts combustion with an electrical spark. Ignition coil Produces the high voltage needed by a spark plug. Diesel glow plug Adds local heat to help a diesel engine’s combustion conditions. Fuel-vapor purge valve Meters stored fuel vapor from the vapor system into the engine. Fuel-vapor charcoal canister Temporarily traps fuel vapor for later controlled burning.
Cooling & lubrication
Coolant radiator Releases engine-coolant heat into outside air. Coolant pump Circulates coolant through a thermal-management circuit. Coolant thermostat Regulates coolant routing as operating temperature changes. Coolant expansion tank Provides space for coolant expansion and a filling point. Electric cooling fan Pulls air through heat exchangers when needed. Coolant hose Connects coolant components while allowing movement. Engine oil pump Circulates lubricating oil to loaded moving parts. Engine oil filter Removes particles from circulating engine oil. Engine oil sump Collects returning engine oil for the lubrication system. Engine oil cooler Transfers heat away from engine oil. Oil-pressure sensor Reports lubrication-system pressure or a pressure threshold. Electronic oil-level sensor Measures engine-oil level for the vehicle’s display. Accessory drive belt Transfers engine rotation to belt-driven accessories. Accessory-belt tensioner Keeps suitable tension on the accessory belt.
Exhaust & emissions
Exhaust manifold Collects burned gas from the cylinders. Turbo downpipe Carries gas from the turbo toward exhaust treatment. Catalytic converter Helps convert certain exhaust pollutants into less harmful gases. Oxygen sensor Measures exhaust oxygen to support mixture or catalyst monitoring. Diesel particulate filter Traps soot particles from diesel exhaust. Petrol particulate filter Traps particles in the exhaust of equipped petrol engines. SCR catalyst Helps reduce nitrogen oxides using a controlled reducing-agent system. AdBlue reservoir Stores the reducing-agent solution used by an SCR system. Rear exhaust silencer Reduces exhaust noise before gas leaves the tailpipe. Exhaust flap Opens or closes an exhaust path to change sound and back pressure.
Transmission & xDrive
Manual gearbox Lets the driver choose gear ratios between engine and wheels. Steptronic automatic transmission Provides automatic shifts with driver-selectable gear commands on equipped cars. Dual-clutch transmission Uses two clutches to alternate between groups of gears. Manual clutch disc Connects engine torque to a manual transmission through friction. Flywheel Smooths engine rotation and provides a clutch or transmission interface. Torque converter Transfers engine torque through fluid in a compatible automatic gearbox. Transmission heat exchanger Manages automatic-transmission fluid temperature. Propeller shaft Carries rotation along a longitudinal drivetrain. Flexible driveline coupling Cushions torque pulses at a driveline connection. Propeller-shaft center support Supports a multi-section propeller shaft while isolating vibration. Axle differential Lets driven wheels turn at different speeds in a corner. Active M Differential Varies rear-axle differential locking to help manage drive torque. xDrive transfer case Routes drive between axles in applicable all-wheel-drive layouts. Driveshaft half-shaft Carries torque from an axle drive to an individual wheel.
Suspension
Suspension coil spring Supports vehicle weight while allowing wheel movement. Shock absorber Controls how quickly suspension motion settles. Adaptive damper Changes damping behavior under electronic control. Air spring Supports vehicle load using pressurized air. Suspension air compressor Supplies compressed air for a self-leveling suspension. Suspension control arm Guides wheel movement relative to the body. Suspension ball joint Allows a suspension link to pivot in multiple directions. Suspension bushing Allows small controlled movement while isolating road vibration. Anti-roll bar Resists differences in left-right suspension movement. Anti-roll-bar link Connects an anti-roll bar to the suspension. Strut top mount Locates the top of a strut and isolates vibration. Axle carrier / subframe Provides mounting points for suspension and drivetrain assemblies.
Brakes
Brake disc Provides the friction surface that the pads grip. Brake pad Presses friction material against the disc to slow the car. Brake caliper Squeezes the brake pads against the disc. Flexible brake hose Carries hydraulic brake pressure while the wheel moves. Brake-fluid reservoir Stores the fluid supply for the hydraulic braking system. Brake master cylinder Turns pedal input into hydraulic pressure. Brake assistance unit Reduces the pedal effort needed for braking. ABS / DSC hydraulic unit Modulates individual wheel brake pressure for control functions. Brake-pad wear sensor Signals when a monitored pad reaches its sensing stage. Parking-brake actuator Applies a holding brake when the car is parked. M carbon-ceramic brakes Use specialized discs designed for demanding thermal conditions. Brake line Carries brake fluid pressure from the master cylinder to each wheel. Brake shield Protects the disc from debris and guides cooling air.
Steering
Steering rack Turns steering input into side-to-side movement at the front wheels. Steering tie rod Transfers rack movement to the wheel carrier. Steering column Connects the steering wheel to the steering gear. Electric steering-assist motor Adds controlled force to help turn the wheels. Steering-angle sensor Reports steering position for vehicle-control systems. Integral Active Steering rear actuator Adjusts rear-wheel steering angle on equipped cars.
Wheels & tires
Road wheel Supports the tire and connects it to the hub. Road tire Provides the car’s contact and grip with the road. Run-flat tire Can support restricted continued driving after certain pressure-loss events. Tire-pressure sensor Reports pressure from inside a wheel on direct-monitoring systems. Wheel bearing Lets the wheel rotate smoothly while supporting vehicle loads. Wheel hub Provides the wheel’s centered, load-carrying attachment. Wheel-speed sensor Reports each monitored wheel’s rotation to control systems. Wheel bolt Clamps the wheel to the hub. Tyre tread Grips the road and clears water from under the tyre.
Electrical & electronics
Low-voltage battery Stores energy for vehicle electronics and starting-related functions. Alternator Generates electricity while a combustion engine runs. Starter motor Turns a combustion engine fast enough to begin running. DME engine controller Coordinates the petrol engine’s fuel, ignition and other control functions. Body electronics controller Coordinates many comfort and body electrical functions. Electrical fuse Interrupts an overloaded electrical circuit. Electrical relay Uses a control signal to switch another electrical circuit. Intelligent Battery Sensor Reports low-voltage battery operating information to energy management. Wiring harness Routes power and signals between vehicle components. Vehicle communication network Lets electronic modules exchange coordinated messages. iDrive head unit Runs major infotainment and interface functions. iDrive controller Lets the driver navigate compatible infotainment menus by touch and rotation. Vehicle camera Provides images for parking or driver-assistance functions. Intelligent alternator control Charges the battery mainly when it costs the engine least.
Safety & assistance
Airbag module Provides a rapidly deployed cushion in certain collisions. Seat belt Restrains an occupant in the intended seating position. Seat-belt pretensioner Removes belt slack during defined safety events. Crash sensor Reports collision-related motion or pressure to restraint control. Driver-assistance radar Measures objects for equipped assistance functions. Parking ultrasonic sensor Measures nearby objects for parking support. Yaw-rate sensor Measures how quickly the car rotates around its vertical axis. ISOFIX child-seat anchorage Provides defined attachment points for compatible child restraints. Head restraint Supports the head as part of the seat’s occupant-protection design.
Cabin & comfort
M steering wheel Provides the driver’s steering grip and fitted control buttons. Steering-wheel shift paddle Sends a manual gear-change request on compatible transmissions. Instrument cluster Shows driving speed, warnings and key vehicle information. Head-up display Projects selected information into the driver’s forward view. Cabin microfilter Filters air entering the passenger compartment. Cabin blower motor Moves air through the climate-control system. Air-conditioning compressor Circulates refrigerant for cabin cooling. Air-conditioning condenser Releases refrigerant heat to outside air. Air-conditioning evaporator Absorbs cabin-air heat as refrigerant evaporates. Cabin heater heat exchanger Transfers coolant heat into cabin air on equipped systems. Electric seat-adjustment motor Moves a powered seat adjustment mechanism. Window regulator Raises and lowers the door glass. Door latch assembly Holds the door closed and releases it when commanded.
Exterior & lighting
BMW kidney grille Forms BMW’s recognizable paired front-face graphic and may admit cooling air. Hofmeister kink Creates the returning angle in a BMW’s rear side-window line. BMW roundel Identifies the car with BMW’s circular brand emblem. Corona-ring / angel-eye light signature Creates a recognizable illuminated headlight outline on equipped BMWs. Headlight assembly Lights the road and provides defined front lighting functions. Adaptive headlight control Changes lighting behavior to suit supported driving conditions. Rear light assembly Communicates presence, braking and other rear lighting signals. Exterior mirror assembly Provides a rearward side view and fitted assistance features. Windshield wiper motor Drives the blades that clear the windshield. Screen-wash pump Sends cleaning fluid toward the glass nozzles. Active grille shutter Changes front cooling airflow through controlled openings. Underbody cover Guides under-car airflow and shields components from some road debris.
Electric drive & charging
High-voltage traction battery Stores the energy used to propel an electric or plug-in-hybrid BMW. Traction-battery cell Stores electrical energy through reversible chemical reactions. Battery module / cell assembly Organizes cells into a defined battery assembly where the architecture uses modules. Battery-management system Monitors battery conditions and sets permitted operating limits. Traction inverter Controls electrical power exchanged with the drive motor. Electric traction motor Turns electrical energy into driving rotation. Electric-motor stator Creates the controlled magnetic field in the fixed part of a motor. Electric-motor rotor Provides the rotating magnetic assembly that delivers motor torque. Onboard AC charger Converts incoming AC power into charging power for the battery. High-to-low-voltage converter Supplies the low-voltage network from the traction battery. Charging inlet / charge port Connects the car to compatible charging equipment. Charging-connector lock Holds a compatible charging connector in its intended position. High-voltage contactor Connects or separates sections of the traction-battery power circuit. Electric-drive reduction gear Matches motor rotation to useful wheel torque and speed. Electric-drive thermal system Manages temperatures in the battery, motor and electronics. Vehicle heat-pump system Moves heat to support efficient cabin or thermal conditioning when fitted. Regenerative braking Recovers some motion energy as electricity while slowing the car.