March 2007
Updated: CarMD diagnostic tool
This code reader might not be the best medicine
The CarMD is a handheld device that can tell you why the "check engine" light in your car is on and, through the Internet,
advise you about the repairs that are needed, and give you a cost estimate for parts and labor. Although marketed as a breakthrough
product, there are a number of diagnostic tools that are better, based on Consumer Reports testing.
To use, the CarMD ($90) is plugged into the On-Board Diagnostics (OBD-II) port that has been installed on new cars since 1996. Usually found somewhere near the bottom of the dashboard (look in your owner's manual), the OBD-II port is used by professional automotive technicians to determine the cause of a variety of mechanical, electrical, and emissions-related problems. Such problems are often flagged to drivers through the check-engine light in the instrument panel. Those issues can activate a diagnostic code in the engine-control computer, which identifies the problem or general trouble area.
In addition to displaying the diagnostic code, one of the three LEDs on the CarMD will light up. Green means there are no trouble codes, yellow means there is a possible problem, and red means service is required. To get more information if a yellow or red LED illuminates, the product can be connected to a Windows-based PC, where it will automatically log on to CarMD's Web site through supplied software to provide a description of the code, a probable diagnosis, and cost estimate. Users can register up to three vehicles per CarMD device, enabling up to six diagnostic reports to be produced a month. If you are not near a computer, you can also place a toll-free call to CarMD's Automotive Service Excellence (ASE)-certified technicians to ask a question or get a report.
WHAT OUR TESTING FOUND
While the CarMD performed as promised, Consumer Reports testing revealed some issues that could limit its usefulness to some car owners:
Mechanical knowledge. Like any diagnostic tool, CarMD can only provide a probable cause and suggested fix. As a result, a certain amount of mechanical knowledge is needed to interpret its findings, or you might end up asking your mechanic for repairs that you don't need.
Turning the "check engine" light off. Unlike many other OBD-II diagnostic tools, CarMD cannot reset a check-engine light, so all problems that activate a permanent trouble code--even an easy-to-fix problem such as tightening a loose gas cap--require visiting a service station and potentially paying to have the light reset.
Compatibility. Another concern we had is that its shape prohibited our using the device on 1 of the 10 cars we used for the test. Check CarMD's compatibility with your vehicle before you buy.
THE BOTTOM LINE
Consumer Reports has tested several code-reading devices that are similar to the CarMD in function, but without the convenient printout and technical support--much of which can be found free online. One of those other readers might be a better bet. For a few dollars more than the CarMD's price, the Actron CP9125 we tested will display the problem code and allow you to reset the check-engine light--a valued feature for do-it-yourselfers. So will the more expensive Innova 3030. Keep in mind that the light will come back on if repairs are not made.
To use, the CarMD ($90) is plugged into the On-Board Diagnostics (OBD-II) port that has been installed on new cars since 1996. Usually found somewhere near the bottom of the dashboard (look in your owner's manual), the OBD-II port is used by professional automotive technicians to determine the cause of a variety of mechanical, electrical, and emissions-related problems. Such problems are often flagged to drivers through the check-engine light in the instrument panel. Those issues can activate a diagnostic code in the engine-control computer, which identifies the problem or general trouble area.
In addition to displaying the diagnostic code, one of the three LEDs on the CarMD will light up. Green means there are no trouble codes, yellow means there is a possible problem, and red means service is required. To get more information if a yellow or red LED illuminates, the product can be connected to a Windows-based PC, where it will automatically log on to CarMD's Web site through supplied software to provide a description of the code, a probable diagnosis, and cost estimate. Users can register up to three vehicles per CarMD device, enabling up to six diagnostic reports to be produced a month. If you are not near a computer, you can also place a toll-free call to CarMD's Automotive Service Excellence (ASE)-certified technicians to ask a question or get a report.
WHAT OUR TESTING FOUND
While the CarMD performed as promised, Consumer Reports testing revealed some issues that could limit its usefulness to some car owners:
Mechanical knowledge. Like any diagnostic tool, CarMD can only provide a probable cause and suggested fix. As a result, a certain amount of mechanical knowledge is needed to interpret its findings, or you might end up asking your mechanic for repairs that you don't need.
Turning the "check engine" light off. Unlike many other OBD-II diagnostic tools, CarMD cannot reset a check-engine light, so all problems that activate a permanent trouble code--even an easy-to-fix problem such as tightening a loose gas cap--require visiting a service station and potentially paying to have the light reset.
Compatibility. Another concern we had is that its shape prohibited our using the device on 1 of the 10 cars we used for the test. Check CarMD's compatibility with your vehicle before you buy.
THE BOTTOM LINE
Consumer Reports has tested several code-reading devices that are similar to the CarMD in function, but without the convenient printout and technical support--much of which can be found free online. One of those other readers might be a better bet. For a few dollars more than the CarMD's price, the Actron CP9125 we tested will display the problem code and allow you to reset the check-engine light--a valued feature for do-it-yourselfers. So will the more expensive Innova 3030. Keep in mind that the light will come back on if repairs are not made.
