Engine Diagnostics on your GPS or iPhone

The Garmin ecoRoute HD Vehicle Diagnostics Communicator is a cable which plugs between some of the Garmin nüvi GPS units and a car's On-Board Diagnostics (OBD) interface, turning the GPS screen into a car diagnostic system.

The goLINK OBD-II is a similar cable to interface for an Apple iPhone or iTouch and the OBDLink Bluetooth interfaces via Bluetooth. You can also build the blueOBD Kit and interface it to an Android phone.

If you want a dedicated device there is the Auterra DashDyno which has its own screen and can be fitted into the car dash board. Linear Logic make a cheaper dash mounted unit, but without GPS.

If all you want to do is actually work out what is wrong with your car, rather than show off with a flashy display, there are simple low cost calculator like OBD-II Code Readers.

How to Use Car Scan Tools

Popular Mechanics has a good item on "How to Use an Auto Scan Tool" (Mike Allen, July 2008). This describes how to use low cost On-Board Diagnostics (OBD-II) devices plugged into the car to report diagnostic trouble codes (DTCs):

To get started, plug the scan tool into the OBD II connector under the dash. Turn the key on, but don't start the engine. The tool will ask for a number of things such as the VIN, the make and model of the vehicle and the engine type. Follow the onscreen instructions.

You'll get an option to check for trouble codes, as well as a couple of other menu choices. Some higher-end scan tools give you a text explanation of the code onscreen. ...

From: How to Use an Auto Scan Tool", Mike Allen, Popular Mechanics, July 2008