Chevrolet Blazers built after 1996 are equipped with on board diagnostics (OBD II), a system of sensors designed to monitor the emissions performance of your vehicle. When one of these sensors malfunctions it sends a signal called a trouble code to the engine computer. The engine computer then causes the service engine soon light to illuminate. The cause of the malfunction can only be learned by connecting a diagnostic code scanner to the vehicle and scanning the engine computer. The scanner will give you a trouble code which you can decipher by looking in the vehicle’s service manual or consulting online sources.
Park the vehicle on a level surface and apply the parking brake.
Locate the OBD II plug. It will be located underneath the dash between the steering column and the driver’s side door.
Slide the diagnostic code scanner’s cable into the OBD II plug on the vehicle.
Insert the key into the ignition and turn it to the “run” position, but do not start the engine.
Press the button on the scanner that reads “scan for trouble codes” or something similar. The code or codes will appear on screen as a "P" followed by four numbers such as P0171. Wait for the scanner to finish scanning.
Look up the trouble code in a service manual or search the internet. If doing an internet search include the make model and year of your vehicle along with the trouble code. Sometimes the code might pinpoint the exact component that needs to be replaced, other times the code will only pinpoint a specific subsystem and you might need to do further troubleshooting.
Press the button on the scanner that reads “clear trouble codes” or something similar. This will clear all codes from the computer's memory.
Pull the cable from the OBD II plug.
