Which method is appropriate for confirming emissions failures indicated by stored unconfirmed trouble codes?

The appropriate method for confirming emissions failures indicated by stored unconfirmed trouble codes is Mode 6. This mode provides detailed information regarding monitored parameters and their performance, which can help technicians assess whether a vehicle has passed or failed specific emissions tests. Mode 6 data includes information on the results of various onboard diagnostics tests that monitor critical emissions components, allowing for a more thorough diagnosis.

Using Mode 6 is crucial because it allows technicians to evaluate the vehicle's readiness for emissions testing and identify any issues that may not trigger a confirmed trouble code but could still lead to emissions failures. This data can help in verifying the operational status of components required for compliance with emissions standards.

The other options—Modes 5, 7, and 8—serve different purposes within onboard diagnostics. Mode 5 is related to the monitoring of vehicle speed and its effects on emissions, while Mode 7 pertains to the identification of component defects in real time. Mode 8 does not focus specifically on emissions failures, making Mode 6 the most relevant choice in this context for confirming emissions issues indicated by unconfirmed trouble codes.