What is a common diagnostic tool used for automatic transmission issues?

An OBD-II scanner is a common diagnostic tool used for automatic transmission issues because it connects to the vehicle's onboard diagnostic system to retrieve trouble codes, which can indicate specific problems within the transmission or other systems in the vehicle. This tool not only provides information about fault codes but can also include real-time data about various sensors and system performance. The ability to read transmission-related codes allows mechanics to pinpoint issues more efficiently, leading to faster diagnostics and repairs.

The other tools listed have different purposes and are not typically used for diagnosing automatic transmission problems. A multimeter is primarily used to measure electrical properties, such as voltage and resistance, which is useful for electrical troubleshooting but not specific to transmission diagnostics. A compression gauge measures engine cylinder pressure, which is relevant for engine health but does not provide insights into transmission performance. A payload monitor is used to assess load limits and distribution, which is relevant for vehicle capacity but does not relate directly to transmission issues. Therefore, the OBD-II scanner is the most applicable tool for diagnosing automatic transmission troubles.