To use either device, it must be plugged into the On-Board Diagnostics II port that all new cars have been equipped with since 1996. Originally implemented to monitor emission system performance, the OBDII port is also where mechanics connect to a car's diagnostic network. From this, technicians can check systems as varied as emissions, powertrain, and safety equipment for proper operation. Most OBDII ports are located in the lower part of the dashboard near the driver's seat. If the port is in another location, a sticker should indicate where it can be found.

The small CarChipE/X is roughly the same size as two stacked nine-volt batteries, so it can be plugged directly into the OBDll port. The RS-1000 is proportioned like a stack of six CD jewel cases, and it must be connected to the port using a supplied cable. We mounted ours under the driver's seat and secured it with Velcro strips that also come with the unit. Care must be taken to safely route the cable without interfering with the driver.

What we found

Both products worked basically as advertised and were accurate when measured against our test equipment. Warning levels are preset at the factory, and each device allows those limits to be raised or lowered with included software.

An advantage of the CarChipE/X is that it can be used to reset a "check engine" light and to read diagnostic codes. (The numeric codes can be translated with information available online.) These features can help users make a more informed decision as to when an immediate trip to the mechanic is necessary. Tipped off by the OBDII data, mechanically inclined owners may even be able to perform some necessary repairs with further investigation.