Q: I see you recommend using a professional scanner to see what’s wrong with a car. Can you explain the difference between these and the one I’ve bought at the auto parts store?

A: Practically the entire car is now connected in a network that can be accessed using a scan tool. These tools have become an essential part of diagnosing engine, transmission, brake, air conditioning, lighting and accessory systems just to name a few.

The inexpensive tool you purchased is likely an OBD-II generic scan tool. These are capable of obtaining and clearing emissions related diagnostic trouble codes (generic and manufacturer specified), checking system readiness (completion of onboard diagnostic tests for various systems- important for emissions certification), and viewing a freeze frame (data captured when a code sets). Some tools may indicate diagnostic trouble code definitions and other helpful features. Some higher-end generic scan tools also provide ABS capability for certain vehicle makes and additional OBD-II features such as Mode 6 (noncontinuous monitor test results). Mode 6 is helpful with intermittent problems, as one can check to see how close a system or component came to passing or failing a test.

A professional grade (aftermarket) or manufacturer-specific scan tool goes far beyond the OBD-II system, allowing access to the manufacturer’s in-depth information, tests and calibration functions for engine systems such as variable valve timing, electronic throttle control and intake manifold tuning, turbocharger systems. These systems can vary by manufacturer, so specific access is needed. Examples of capabilities beyond simply looking at data includes performing an evaporative system leak check, a crank sensor angle learn procedure, running a cylinder balance test and commanding the camshaft actuator to verify phasing accuracy.

A top-notch aftermarket or manufacturer-specific scan tool also allows access to transmission and all-wheel-drive systems, braking, stability control, traction control and other under-car systems. Also, body electronics such as lighting, instrumentation, climate control, SRS (air bags), communication and navigation systems are typically accessed, diagnosed and verified using a scan tool. Examples include performing a radar aiming procedure related to the adaptive cruise control or collision mitigation system, initiating a new ignition key to the immobilizer system, ABS system bleeding, initiating a new tire pressure monitoring sensor, checking for a correct passenger side window switch input, controlling the defroster mode door to fully open and sweeping the instrument panel gauges up to 50, and then 100 percent. Being able to see if incoming switch requests are successful and performing output commands rules out a lot of unnecessary disassembly and testing, as one can quickly determine if the fault may be caused by a switch, the network, or actuator.

An OBD-II generic scan tool is a great addition to anyone’s toolbox.