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Air Intake and Metering

Everything between the outside air and the inlet valve: filtration, ducting, the throttle, and the sensors that measure how much air is actually getting in. Almost every fuelling calculation starts from a measurement made here, which is why faults in this system produce symptoms that look like they belong somewhere else.

18 components · 7 live parameters

Fuel Delivery

Tank to injector tip — lift pump, filter, high-pressure pump, rail, regulator and injectors. On direct-injection and diesel systems the pressures involved are extreme, which makes both the diagnostic care and the failure consequences greater than on older port-injected engines.

22 components · 15 live parameters

Ignition

Spark generation and delivery: coils, plugs, leads, and the crank and cam signals that decide when the spark happens. Faults here show up as misfires, and misfires are the fault class most likely to damage a catalytic converter.

9 components · 1 live parameter

Valve Timing and Actuation

Variable valve timing and lift — phasers, oil control solenoids, timing chains and their tensioners. This system runs on oil pressure, so it fails the way an oil-pressure system fails: gradually, and often because of an overdue service rather than a broken part.

6 components

Forced Induction

Turbochargers and superchargers with their wastegates, bypass valves, boost control solenoids, intercoolers and charge pipework. The single most common fault in this system is a leak somewhere along a long, hot, pressurised path — not a failed turbocharger.

10 components

Exhaust and Emissions

Everything downstream of the exhaust valve, plus the systems that clean up combustion: oxygen sensors, catalytic converters, EGR and evaporative emissions. Many faults reported here are honest measurements of a problem that originates upstream in fuelling or ignition.

41 components · 4 live parameters

Engine Mechanical

The moving parts themselves — pistons, rings, valves, bearings, and the timing drive. Diagnostics reach these only indirectly, by measuring the consequences: low compression, weak cylinder contribution, or a timing correlation that no longer holds.

8 components

Cooling

Coolant circulation and temperature regulation — thermostat, water pump, radiator, fans and the temperature sensors the control module depends on. A thermostat stuck open costs fuel quietly for years; one stuck closed destroys an engine in minutes.

15 components · 1 live parameter

Engine Management and Sensors

The control module, its sensor supplies and grounds, and the signals it uses to reason about everything else. A single failed five-volt reference can set half a dozen unrelated-looking sensor codes at once, which is why shared supplies are checked before individual sensors.

9 components · 24 live parameters

Transmission

Gear selection and torque transfer — solenoids, torque converter, fluid temperature and pressure control. Overheated transmission fluid causes cumulative damage that shows up long after the episode that caused it.

44 components

Electrical and Charging

Supplies, grounds, relays, fuses and the harness itself. Worth its own system because wiring is the most common cause across the entire corpus — connectors and chafed looms account for more stored codes than any component category.

32 components · 2 live parameters

Body, Interior and Safety

The modules that run everything outside the powertrain and the chassis: lighting, locking, windows, the alarm and immobiliser, the instrument cluster, the climate system, and the restraints that fire in a crash. Two things characterise faults here. They arrive in clusters, because one module usually runs several unrelated conveniences, so a spread of odd electrical symptoms is far more often one fault than many. And they live in the cabin, which makes water from a blocked drain, a leaking heater or a perished screen seal a leading cause rather than an exotic one.

29 components

Braking, Steering and Suspension

The chassis hardware the driver actually steers and stops with, and the electronics layered over it. The consistent thing worth knowing about this system is that the electronics sit on top of a mechanical arrangement rather than replacing it: the brakes are hydraulic underneath the anti-lock valves, and the steering rack is mechanically connected underneath the assistance motor. So a failure here usually removes help rather than function — which is why the car still stops and still steers, and why what has actually been lost only shows up at the moment it was needed.

18 components

Vehicle and Chassis Sensors

Signals that describe the vehicle rather than the engine: road speed, ambient conditions, and the wheel-speed data that misfire detection borrows to tell a rough road from a genuine misfire.

8 components · 2 live parameters

Hybrid Propulsion

Drive motors, generators, power electronics and the high-voltage battery that feeds them. This system is different in kind from everything else in the corpus for one reason: it runs at several hundred volts DC, which is lethal to touch in a way nothing else on a vehicle is. The orange cabling is a warning, not a styling choice, and no part of this system is suitable for home repair or for a workshop without high-voltage training and equipment. It is also, in ordinary use, among the most reliable systems on the vehicle — the failures that do occur are usually in the cooling and control circuits around the high-voltage components rather than in the components themselves.

25 components