What is the purpose of diagnostic trouble codes?

• A. Identify faulty sensors and systems
• B. Display fuel economy data
• C. Set ambient cabin temperature
• D. Adjust transmission gearing

Answer: (A)

Diagnostic trouble codes are the vehicle’s way of signaling that a fault has been detected by the onboard computer. They identify which sensor or system is experiencing a problem, guiding technicians straight to the area that needs inspection and repair rather than prescribing adjustments or displaying performance data. They aren’t used to show fuel economy, set cabin temperature, or change transmission gearing. For example, a fault in the engine’s sensor system will trigger a specific code that points to that circuit, helping you troubleshoot efficiently. After repair, the codes can be cleared and a drive cycle can confirm the issue is resolved.