How to Use a GM Code Reader
If your General Motors vehicle has a problem, a malfunction indicator light will illuminate on the instrument panel, such as "Check Engine Light" or "Service Engine Soon," letting you know that you might need to fix it yourself or take it to a mechanic or dealer for service. There are other codes that you can see by using an Equus electronic device to read GM onboard diagnostics codes from the car's computer to help you learn what's wrong.
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Instructions
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Check the engine oil, power steering fluid, engine coolant and other fluids and replenish as needed, examine the air filter to make sure it is clean, see that all belts are in good shape and look for any other mechanical problems before using the code reader. Mechanical problems and low levels of oil and other fluids can cause fault codes.
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Connect the code reader's cable to the vehicle's test connector, which is usually located under the dashboard on the driver's side. The reader will turn on automatically. Press the "Power/Link" button to turn on the reader, and then press the "Enter/FF" button.
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Press the up and down buttons to highlight the "Current Selection/Select New Vehicle" option then press the "Enter/FF" button. Press the up and down buttons to select the model year of your vehicle then press the "Enter/FF" button. A message will appear, reading "Enter the 8th digit of VIN."
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Press the up and down buttons to highlight the eight number of the vehicle identification number then press the "Enter/FF" button. If you don't know the VIN, locate it on the driver's side of the dashboard near the window. Press the up and down buttons to highlight the fourth digit of the VIN if you are prompted to do sothen press the "Enter/FF" button. The "Current Selection/New Vehicle Selection" screen will then display your vehicle's model.
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Press the up and down buttons to highlight "Current Selection," then turn the ignition key to the "On" position. Don't start the engine.
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Press the "Power/Link" button on the code reader. It will automatically start checking the vehicle's computer. Within one minute, the reader will receive any diagnostic trouble codes, which will appear in its LCD display. Data will refresh every 30 seconds from the vehicle's computer, during which a message will appear reading "One Moment, Auto Link in Progress." If no codes are in the vehicle's computer memory, the message "No DTCs are Presently Stored in the Vehicle's Computer" will appear.
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Look at the display's upper right corner, which will show the number of the code being displayed, how many codes have been retrieved from the computer and the type of code. "G" stands for generic, "E" sands for enhanced codes or codes specified by the manufacturer.
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Look at the LCD lights for more information about the code reader's condition. A green light signifies that the engine systems are OK and working normally. A yellow light means there is a pending code, which means that the car has recorded one instance of a trouble code in the first trip of a two-trip code. If the code doesn't happen again during a second trip, the code automatically is erased. A red light means there is a problem in at least one of the vehicle's systems and the code will appear in the LCD display, such as "Mass Air Flow Sensor Failure."
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Press the "DTC Scroll" button to advance through additional codes if there are any more. Note that code 12 will always appear in the reader and has one of two meanings: If code 12 is the only code retrieved and your vehicle starts up OK, code 12 indicates a system pass, with all systems functioning properly. If there is a code 12 and your engine doesn't start, it can mean there is a problem with the ignition control system, which you might need to have serviced.
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Disconnect the cable from the vehicle and turn the ignition key to the "Off" position after you have finished reading codes in the device.
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