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Scan tools can provide vital data from vehicle

| Saturday, March 9, 2013, 12:01 a.m.

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?

— Sam Bass

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 cost as much as $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 to $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);

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

• Check calibration status;

• 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 might 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. 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 limited but 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 often are needed to 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.

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at under-the-hood@earthlink.net; he cannot make personal replies.

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