During an instruction panel gauge test, the technician observes that the engine temperature gauge is reading 200 F (93 C) on a cold engine. Who is correct regarding the possible diagnosis?

The reasoning behind selecting the correct answer lies in the significance of using a scan tool for diagnostics. When the engine temperature gauge reads abnormally, such as 200°F on a cold engine, it suggests that there may be an issue with the temperature reading or the overall engine temperature. Utilizing a scan tool allows the technician to access the engine control module (ECM) data and compare sensor readings, which can help determine if the gauge is faulty or if there is an actual issue with the engine.

While an open coolant thermostat can indeed lead to abnormal temperature readings—by preventing the engine from reaching its normal operating temperature—this option does not directly address the immediate need for comparison data in diagnosing the gauge's incorrect reading. The scan tool allows for a broader perspective on engine performance and sensor functionality, making it a valuable tool in this diagnostic scenario.

Thus, focusing on the capabilities of the scan tool to contrast readings is the most pertinent and effective approach in determining the source of the false gauge reading.