What may an inspector check if a vehicle has failed its emissions test multiple times?

When a vehicle fails its emissions test multiple times, it is essential for an inspector to focus on the vehicle's On-Board Diagnostics II (OBDII) system. Inspecting for repeated fault codes and incomplete OBDII system tests helps to identify the underlying issues affecting the vehicle's emissions performance.

The OBDII system monitors the performance of the vehicle's engine and emissions control systems. When there are problems, fault codes are generated, providing specific information about which component or system is malfunctioning. An inspector reviewing these error codes can pinpoint issues such as a failing catalytic converter, oxygen sensor malfunctions, or other critical components that impact emissions.

Additionally, checking for incomplete OBDII system tests is vital because it can indicate whether certain systems have been properly evaluated during the testing cycle. If essential systems are marked as incomplete, it suggests that the vehicle may not have undergone the necessary diagnostic checks to ensure it meets emissions standards, thereby contributing to repeated failures.

This approach is much more relevant and effective than assessing factors like fuel grade, tire pressure, or vehicle body condition, which do not directly influence emissions results.