Engine
Turns the energy in fuel into mechanical work. It needs oil, coolant, clean air and a working ignition or fuel injection system.
Models and Technology
Models and Technology
This section explains what a modern car is made of and where the technologies owners deal with during maintenance came from: the catalytic converter, emissions standards and on-board diagnostics.
A car's main systems
This is a simplified breakdown: components vary between models and powertrain types.
Transmission
Clutch or torque converter, gearbox and driveshafts. It delivers torque to the wheels; gearboxes and differentials also have oil with its own service schedule.
Suspension and steering
Shocks, springs, control arms, ball joints and tie rods. They handle stability and comfort; wear shows up as clunks and the car pulling to one side.
Brakes
Pads, rotors or drums, calipers, hydraulics filled with brake fluid, and ABS. The most important active safety system.
Electrical system
Battery, alternator, starter, control modules and sensors. On-board diagnostics runs through them as well.
Exhaust system
Carries exhaust gases away and reduces noise and harmful emissions. It includes the catalytic converter and oxygen sensors.
The components people ask about most
- Catalytic converter
- An exhaust component that chemically converts harmful exhaust gases into less harmful ones. Its performance affects whether the car meets its emissions class.
- Oxygen sensor (lambda sensor)
- Measures oxygen in the exhaust. It helps the control module keep the air-fuel mixture right and monitor the catalytic converter.
- Engine control module (ECM)
- The computer that controls fuel injection and ignition based on sensor signals and stores trouble codes.
- Diagnostic port
- A standard connector in the cabin that a scanner uses to read trouble codes and live system data.
- Malfunction indicator lamp (MIL)
- The "check engine" light on the dashboard. It comes on when on-board diagnostics detects a fault, including one that affects emissions.
A history of the technology: from the catalytic converter to Euro 6
Five dates that explain why a modern car has a catalytic converter, oxygen sensors and a diagnostic port.
- 1975
In the US, catalytic converters begin to be installed on new cars on a mass scale, starting with the 1975 model year.
- 1992
Europe introduces the Euro 1 emissions standard, the first stage of EU-wide emissions requirements.
- 1996
OBD-II on-board diagnostics becomes mandatory for new passenger cars in the US starting with the 1996 model year.
- 2001
The European on-board diagnostics standard, EOBD, begins to apply to gasoline cars in the EU.
- 2014
Euro 6 standards take effect for new types of passenger cars in Europe.
Source US and EU emissions standards; OBD-II and EOBD on-board diagnostics standards
Why this matters to owners
The catalytic converter, oxygen sensors and on-board diagnostics work as one system: the control module monitors the exhaust and reports faults through the dashboard warning light. That is why tampering with one component, such as the exhaust system, affects how the others work.
A car's emissions class is listed in its registration documents. Modifications that affect emissions can mean the car no longer meets that class; see the safety section for more.
Questions about the technology
Does my car have a diagnostic port?
Most passenger cars from recent decades do; its location is shown in the owner's manual. For older cars and some regional versions, check the manufacturer's documentation.
What is the difference between OBD-II and EOBD?
They are the American and European on-board diagnostics standards and serve a similar purpose: monitoring systems that affect emissions and storing trouble codes that a scanner reads through the port.
Sources
- Vehicle owner's manual
- Automakers' websites
- Euro 1 to Euro 6 emissions standards
- OBD-II and EOBD on-board diagnostics standards
This site does not replace your vehicle's owner's manual or maintenance schedule: take service intervals, fluid capacities, torque specs and fluid specifications only from there. Check design and emissions requirements with official sources.