What mode should a technician use to check real-time sensor data, including fuel trims and oxygen sensor readings, when diagnosing high NOx emissions?

In the context of diagnosing high NOx emissions, using Mode 1 is the most appropriate choice. Mode 1, often referred to as the "Live Data" or "Real-Time Data" mode, allows the technician to access and view real-time data from various sensors within the vehicle's engine management system. This includes critical information such as fuel trims and oxygen sensor readings, which are essential for understanding how the engine is operating and for identifying any issues that could lead to elevated NOx emissions.

High NOx emissions often indicate problems related to combustion efficiency or the after-treatment system. By monitoring the fuel trims, which reflect the air-fuel mixture adjustments the engine control unit (ECU) is making, alongside oxygen sensor data that indicates the level of oxygen present in the exhaust, the technician can better ascertain whether the engine is running too lean or too rich. This is crucial for pinpointing the root cause of the emissions issue.

The other modes typically do not provide this real-time data. For instance, Mode 2 may focus on standard parameters and diagnostic trouble codes but lacks the capability to offer immediate sensor output. Modes 3 and 4 may relate to additional functions such as generic or manufacturer-specific diagnostic information, but they do not target the real