A diagnostic test for a car is typically performed using an OBD-II (On-Board Diagnostics) scanner. Here’s how it works:

• Connect the Scanner: The mechanic or technician plugs an OBD-II scanner into the car's OBD port, usually located under the dashboard near the driver's seat. This port connects to the car's onboard computer system.
• Read Error Codes: The scanner communicates with the car's computer to read any stored diagnostic trouble codes (DTCs). These codes are generated when the car’s system detects a malfunction or abnormal readings in specific parts of the vehicle, such as the engine, transmission, or sensors.
• Interpret the Codes: Each code corresponds to a specific problem, like issues with the oxygen sensor, ignition coil, or fuel system. The technician uses a reference guide or database to interpret these codes.
• Clear Codes (Optional): After repairs or troubleshooting, the technician can clear the codes from the system. However, the root cause of the issue must be resolved first, as the car may continue to have the same problem and trigger new codes.
• Further Testing: Depending on the codes, additional tests or physical inspections may be performed to identify the specific cause of the problem.

Diagnostic tests help identify issues early on, making it easier to fix problems before they lead to more serious and expensive repairs.

A "tune-up" is a series of checks and adjustments performed to keep your car’s engine running well. Depending on your car's age and model, tune-ups may be less frequent in newer cars, as many modern vehicles are designed to require less frequent adjustments. However, here's what a tune-up generally covers:

• Spark Plugs: Inspecting and replacing spark plugs, which are responsible for igniting the air-fuel mixture in the engine. Worn spark plugs can lead to poor engine performance, misfires, and decreased fuel efficiency.
• Air Filter: Replacing or cleaning the air filter to ensure proper airflow into the engine. A clogged air filter can reduce fuel efficiency and performance.
• Fuel Filter: Replacing the fuel filter to ensure that contaminants are filtered out of the fuel before it enters the engine. A dirty fuel filter can cause poor engine performance and even damage the fuel injectors.
• Timing and Ignition System: Checking the ignition timing and ensuring that the distributor cap, rotor, and ignition wires are in good condition. This helps maintain proper combustion and engine performance.
• Throttle and Idle Speed: Ensuring the throttle body is clean and that the idle speed is correctly adjusted for optimal engine performance.
• Fluid Check: Checking and topping up essential fluids, such as engine oil, transmission fluid, coolant, and brake fluid, ensuring they’re at proper levels.

Regular maintenance is ongoing care for your car to keep it in good working order. Here are the common tasks involved:

• Oil Change: Regular oil changes (every 3,000 to 7,000 miles, depending on the vehicle and type of oil) are essential for lubricating the engine and preventing wear. The oil filter is typically replaced during this process as well.
• Tire Maintenance: Rotating your tires every 6,000 to 8,000 miles helps promote even tire wear, ensuring better handling and extending tire life. Also, checking tire pressure regularly and ensuring they’re properly inflated is crucial for safety and fuel efficiency.
• Brakes Inspection: Regularly inspecting the brake pads, rotors, and fluid. Brake pads wear over time, so they may need replacement to ensure safe braking performance.
• Battery Check: Checking the battery for corrosion and ensuring it has enough charge to prevent unexpected breakdowns.
• Fluid Checks: Apart from oil, other fluids like transmission fluid, coolant, brake fluid, and power steering fluid need to be regularly checked and topped off or replaced if necessary.
• Belts and Hoses: Inspecting and replacing worn or cracked belts and hoses is important to avoid unexpected breakdowns, as they play a key role in the engine and other systems.
• Lights and Signals: Ensuring headlights, brake lights, turn signals, and other lights are in working order for safety.

• Air Conditioning and Heating: Periodically checking and servicing the A/C and heating systems to ensure they function properly.