Q: I have three different vehicles that I try to maintain, along with trying to pass vehicle system enigmas along to my sons and their assorted vehicles. What would be a “quality” OBD-II scan tool for use, in a variety of cars and trucks, now and into the near future?

A: This is a fun topic, as these tools keep getting better and better regardless of brand. A scan tool allows one to communicate with a vehicle’s engine management and other computers. Scan tools come in basically four formats: OBD-II compliant, which are inexpensive and home-tech friendly; PC- and smartphone-compatible modules; professional-grade aftermarket; and manufacturer-specified, which can hit $10,000.

U.S. vehicles built since 1996 are required to communicate via a standardized protocol, at least for emission-related topics. OBD-II, or On-Board Diagnostics 2, generic scan tools are widely available for $40-$200 and allow a number of functions:

• Checking and clearing pending or current emission-related diagnostic trouble codes, observe emission test readiness;

• Replaying freeze-frame data, a snapshot of engine data taken by the vehicle when an emission fault occurs;

• Observing live engine data, which includes only about 15-20 items on most 1996-2004 vehicles and many more since;

• Checking calibration status, and a few other general functions.

Mid-priced OBD-II scan tools do all the above, and likely display trouble code descriptions and manufacturer-specific trouble codes, which begin with P1 and P3. That goes beyond the standardized codes mandated by OBD-II, which begin with P0 and P2. Higher data-refresh rates and more sophisticated display screens often provide the ability to graph data, besides displaying it in list form, which can be helpful to spot a glitch or irregularity. Connecting and printing to a PC may also be possible.

Scan tools approaching the upper end of the price range can look at more detailed information; record and play back data; display bilingual or trilingual information; allow online updating and website access; and hold information for off-car playback. EOBD or European coverage may also be offered, and as prices hit the $200-and-up range, coverage for antilock brake system and supplemental restraint system can be found, as well as coverage for certain, generally domestic pre-1996 OBD-1 vehicles.

It’s important to remember that OBD-II generic information is a small but very useful slice of the whole engine and vehicle pie. It’s great to be able to identify the general cause of an illuminated check-engine light, but additional diagnostic information and testing are often needed to truly nail down the problem. For the price, these tools are magnificent.

If considering a pre-owned or lower-end scan tool, be sure it’s compatible with CAN, a newer communication protocol, and does most of the things mentioned in my description of generic scan tools. Don’t come home with just a code reader.