How to Use a ODB II Code Reader Scan Tool "Check Engine" Light Warning

If you see a "check engine" or a "service engine soon" light in your instrument cluster; your car has stored a diagnostic trouble code. This means the computer system on your vehicle has detected a problem with the various systems it controls. Your car has many different sensors that monitor the various vehicle systems. If the trouble code light has been illuminated your vehicle enters into "limp mode" this means it is running on a predetermined program that causes poor mileage and increased emissions. An engine trouble code reader is an easy to use tool. All 1996 and newer vehicles utilize a "D" style plug-in connector that connects to the code reader. On most vehicles the connector is located at the driver's compartment. Once the code reader is plugged in you can retrieve trouble codes the engine computer has stored in its memory. These codes are the same codes the dealer and repair shops use to replace sensors and clear codes.

1. Malfunction Indicator Lamp

The MIL has illuminated during driving this means there is a malfunction trouble code stored in the vehicle's computer.

2. Locate Your Vehicle's Computer Connector

Locate your vehicle's computer connector (ALDL), most are on the lower driver's side. In some vehicles you might need to look around a little, on the passenger's side, and around the center console under a plastic cover. For more information, check your owner's manual.

3. Connecting to The Computer to Read Codes

Connect your code reader to the under dash connector. The code reader will automatically turn on and prompt you to the next step for code retrieval. Once the code has been identified look up the identification on the trouble code chart supplied with your code reader. After repair has been made clear trouble codes and recheck system. After codes have been cleared the computer system is ready for internal testing, this means that while the car or truck is in operation the onboard computer is performing tests. These tests are called "monitors" most cars have between 4 and 8 monitor systems. The computer goes though its testing procedure in about 40 to 60 miles.

Common Problems

1. After a car repair has been performed the MIL indicator will illuminate because the technician neglected to plug in a sensor.

2. A blown fuse can cause the MIL to illuminate.

3. A shorted sensor can cause the MIL to illuminate.

Diagnostic Testing / How to Scan Trouble Codes

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