What is a diagnostic test on a car?

Here's information about a car diagnostic test:

A car diagnostic test is a procedure that mechanics use to identify issues within a vehicle's systems. It involves connecting a specialized computer, often called a scan tool, to the car's onboard diagnostic (OBD) system. The OBD system monitors various sensors and components throughout the car and stores fault codes when it detects a problem.

During the test, the scan tool reads these diagnostic trouble codes (DTCs), which are standardized codes that correspond to specific malfunctions. For example, a code might indicate a problem with the engine, transmission, anti-lock brakes, or emissions system.

The mechanic then uses these codes, along with their experience and knowledge, to troubleshoot the issue and determine the appropriate repair. A diagnostic test is a starting point, and further investigation may be required to pinpoint the exact cause of the problem.

Modern cars have increasingly complex computer systems, so diagnostic tests are essential for efficient and accurate repairs. Without them, it could be extremely difficult and time-consuming to find the source of a car problem.