What type of diagnostic tool is used to read trouble codes from a vehicle's ECU?

The OBD-II scanner is specifically designed to interface with the On-Board Diagnostics II (OBD-II) system that is standard in most vehicles manufactured after 1996. This tool connects directly to the vehicle's Electronic Control Unit (ECU) and allows technicians to read trouble codes, which indicate issues within various vehicle systems such as the engine, transmission, and emissions controls.

These diagnostics codes, often referred to as Diagnostic Trouble Codes (DTCs), help mechanics identify the nature of the problem. The OBD-II scanner offers the added advantage of providing live data, vehicle performance statistics, and detailed information that go beyond just reading trouble codes, giving technicians a comprehensive view of the vehicle's health.

In contrast, while an OBD-I scanner may be used for older vehicles, it is not compatible with the OBD-II system. A multimeter is a versatile tool for measuring electrical voltage, current, and resistance, but it does not read trouble codes. A code reader might seem like a beneficial tool; however, it typically refers to basic devices that may only read DTCs without the advanced functionality of an OBD-II scanner, which can provide deeper diagnostics.