Technicians use an OBD scanner to connect to the vehicle's onboard computer system. The OBD system continuously monitors various sensors and components, and it stores error codes when abnormalities are detected. The scan helps identify any stored trouble codes that may indicate issues with the engine or related systems.

A visual inspection involves examining key engine components for signs of wear, damage, or leaks. Technicians may inspect belts, hoses, wiring, and fluid levels to identify any visible issues.

This involves measuring the levels of pollutants in the vehicle's exhaust gases. Technicians assess whether the vehicle complies with emission standards and whether there are issues with the combustion process.

The ignition system, including spark plugs, ignition coils, and the distributor, is inspected to ensure proper functioning. Issues with the ignition system can impact engine performance and fuel efficiency.

Technicians inspect the fuel system, including the fuel injectors, fuel pump, and fuel pressure, to ensure proper fuel delivery to the engine. Problems with the fuel system can affect combustion efficiency.

The air intake system is checked for any restrictions or clogs. A clean and unobstructed air intake is essential for proper air-fuel mixture and combustion.

A compression test may be conducted to assess the condition of the engine's internal components, including the cylinders and piston rings. Adequate compression is crucial for efficient combustion.

Technicians verify that the engine's timing, including the timing belt or chain, is within the manufacturer's specifications. Proper timing ensures that engine components work in harmony during the combustion cycle.

The throttle body and idle speed are inspected to ensure smooth idling and responsive throttle operation.

The cooling system is examined to ensure that the engine maintains the correct operating temperature. Issues with the cooling system can lead to overheating and engine damage.