All cars made after 1996 are required to contain an onboard diagnostics (OBD) port. Diagnostic codes are sent through the vehicle's computer and read by diagnostic tools plugged into the OBD port. These tools are used by automotive technicians and automotive parts stores. Parts stores will usually charge for such a service. Diagnostic tools are not cheap but they are an investment that can save hundreds of dollars in do-it-yourself vehicle repairs. They can also save money and headaches when buying a used vehicle.

Car MD

Car MD has some good features to offer in the way of auto diagnostics. Trouble codes can be uploaded to a personal computer through the Car MD website. This website reads the codes and provides recommendations, lists of parts needed, and an estimated cost of labor and repair.

Car MD could be a shady used car salesman's worst nightmare. It can be plugged into any vehicle that was made in 1996 or later. Run a diagnostic test on a used car before buying.

Prices are always subject to change but right now the Car MD website is offering this product for around $100 (CarMD.com, 2009).

Reports by the nonprofit agency ConsumerReports.org reveal that while this tool does work as promised and is a value at the price, consumers will get more out of similar but more expensive diagnostic tools (ConsumerReports.org, 2007).

Pocket Scan

The Pocket Scan CP9125 made by Actron is at present a bit more expensive than Car MD but according to ConsumerReports.org it is a better diagnostic tool. Its superiority comes from the fact that, in addition to running diagnostic tests and making the results understandable for a novice, it is also capable of resetting the "check engine" light. Car MD does not offer this feature. This tool is on the smaller side which makes it easier to fit into place on some vehicles.

Innova 3130

The Innova 3130 scan tool is at the high end of the price scale. This is a volatile and fairly new business model, so prices could change radically in the future, particularly given the current car market, but the creator of this tool is currently selling it for around $300 (Equus.com, 2009). One of the features that makes this device worth the price is the all-in-one display screen. The manual is available for online viewing prior to purchase and it comes with an instructional DVD. This unit can be updated through a personal computer.

comes with an instructional DVD. This unit can be updated through a personal computer.