How to read your own check engine light with our Free Fix Finder Service

Check engine light on? We can help you get a reading yourself.

Borrow an OBD reader to get a Check Engine Light reading with the AutoZone Free Fix Finder Service.

It's a simple task that takes less than two minutes.

How to Check your own Check Engine Light with Fix Finder Self-Service

1. Safety first

Follow these directions carefully. If you’re unsure or unable to execute any of these steps, an AutoZoner will gladly recommend a shop nearby. Make sure you’re being safe. Vehicle should be off, in park, and secure before attempting the reading.

2. Ask to borrow the Scan Tool

It’s also called an OBD reader. An AutoZoner will get it for you and will have some tips for performing the reading.

3. Locate the Data Link Connector (DLC)

This is a 16-pin connector you’ll plug the reader into. It’s usually located under the driver’s side of the dash, but each vehicle is different. Check your owner’s manual or a repair manual if it’s hard to find.

4. Turn on the ignition, but don’t start the engine

For keyless start vehicles, press the START button twice. DO NOT press the brake pedal or the vehicle will start.

5. Wait 5 seconds, then plug in the reader

Connect the cable connector from the scan tool to the vehicle’s DLC. The cable connector is keyed and will only fit one way. You won’t have to flip it to find the right connection. It will be obvious.

6. Let the reader, read

The scan tool will automatically link with your vehicle’s computer. The reader has a small LCD screen. It should say: “read” and then “done.” The time from “read” to “done” is usually 4-5 seconds. Once the screen says “done,” unplug the reader and turn your vehicle off.

Troubleshooting: If the reader LCD is blank, there’s no power in your vehicle’s Data Link Connector. Check your fuse panel and replace any burned-out fuses. If replacing the fuse(s) does not correct the problem, see your vehicle’s repair manual to locate the proper computer (PCM) fuse or circuit and perform any necessary repairs before continuing.

7. Write down vehicle information and mileage

Take note of the year, make, model, engine (if you know it), and mileage of your vehicle. You’ll need this information in a minute.

8. Bring the scan tool back for your free report

Return the tool to an AutoZoner and let them know your vehicle information. The AutoZoner will get the report for you at a Z-Net Terminal, explain the reading, and recommend possible solutions. You’ll also get a printed copy of the report.

OBD-II scanner done reading trouble codes
Scanning car using OBD2 scanner

These lights are visual aids to make it easier for you to get an idea of engine system conditions.

  • Green CHECK – Indicates all engine systems are “OK” and running normally. All monitors on the vehicle are active and are performing their diagnostic testing, and no trouble codes are present.
  • Yellow ? – one of the following
    • Pending code present
    • Monitor status – This means some of the monitors on the vehicle have not yet finished their diagnostic self testing. Complete a full drive cycle to allow all the monitors to run, then come back and try to retrieve the code again.
  • Red X – Indicates a problem with one or more of the vehicle’s systems. The red LED is also used to show that DTC(s) are present. In this case, the Malfunction Indicator (Check Engine) lamp on the vehicle’s instrument panel will light steady on.

Remember to return the scan tool to an AutoZone employee when finished. These tools will not work with any other device other than the Z-Net terminals at AutoZone.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

FREE Loan-A-Tool® program requires returnable deposit. Please note that the tool that you receive after placing an online order may be in a used but operable condition due to the nature of the Loan-A-Tool® program.

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