A code reader is a starting point for understanding a warning light. Choose by vehicle coverage and supported functions, rather than the number of features on the box.
Confirm vehicle coverage
Many US-market passenger vehicles from model year 1996 onward support OBDII, but coverage varies by market, vehicle type and tool. Verify the exact year, make, model and system coverage with the manufacturer.
Decide what you need to read
A basic reader may cover emissions-related engine codes. ABS, airbag, transmission, service-reset and bidirectional functions are separate capabilities; do not assume they are included.
Look at live data and updates
Live data and freeze-frame information can support diagnosis. Check display readability, update methods, included software and any ongoing fees before choosing a tool.
A fault code is a clue
A trouble code identifies a detected condition, not necessarily the part that needs replacing. Use the vehicle service information and an appropriate diagnostic process. Clearing a code does not fix the underlying problem.