A Beginner's Guide to Reading OBD2 Fault Codes with an Autel Scanner

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Guide to Reading OBD2 Fault Codes with an Autel Scanner

If your check engine light is on, your Autel scanner can help you diagnose the problem without opening your car. With OBD2 fault codes, you can see the warning and fix only what is causing the problem. 

Previously, we explored the effectiveness of aftermarket diagnostic tools and shared an automotive diagnostic scanner buying guide to help you understand what to look for when choosing the right equipment. 

Today, we will take that a step further and explain how to actually use an Autel scanner to understand the fault codes your vehicle is reporting.

Not sure how to read and understand OBD2 fault codes with an Autel scanner? Let us walk you through it step by step.

OBD2 Fault Codes

What Do OBD2 Fault Codes Mean on an Autel Scanner?

When a sensor or system isn’t working as it should, your car’s computer (ECU) stores standardised messages called OBD2 (On-Board Diagnostics 2) fault codes, also known as Diagnostic Trouble Codes (DTCs).

  • Codes start with a letter: P (Powertrain), B (Body), C (Chassis), or U (Network).

  • The next digit indicates whether the code is generic (0, 2, 34-39) or manufacturer-specific (1, 30-33).

  • The other digits identify the particular circuit, sensor, or function that is at fault.

For example, P0301 means “Cylinder 1 Misfire Detected” and P0420 means “Catalytic Converter Efficiency Below Threshold”.

How Do I Read OBD2 Fault Codes with an Autel Scanner?

Menu names differ by model, but the process is the same.

  1. Turn off the ignition and plug the scanner into the diagnostic port.
  2. Turn the ignition on (do not start the engine).
  3. Let the scanner identify the car. On many Autel units, it automatically reads the VIN. Make sure it fits your car.
  4. Go into the diagnostics or read codes menu and scan it out.
  5. Write down all the codes, their status, and the freeze frame data before touching anything.
  6. If the scanner does not export a report, scan the screen. You will want the original data if the fault returns.

Choosing the Right Autel Tool for Your Needs

Not all scanners are made equal. Select your tool by use case:

Comparing Autel vs Launch? You can get multi-brand coverage from both. Autel is known for its intuitive UI and regular updates. Launch offers some deep OEM-style functions on some models.

What Else Must You Know Before Using the Autel Diagnostic Tool?

It doesn’t end with knowing fault codes and buying the right automotive diagnostic tools; there is more to it, and you must know it:

1. Stored, Pending, and Permanent Codes

Your Autel scanner usually tags each code with a specific status. 

A pending code means that the computer detected the fault once, but there is no confirmation. A stored code, on the other hand, means the fault has occurred many times. This is when the check engine light is on.

Then there's the permanent code. It relates to emissions and stays in memory until the car confirms the repair, so you can't just clear it with a scanner.

 Freeze frame data gives you a snapshot of the conditions when the fault was recorded. It includes engine speed, coolant temperature, load, and more. This information is super helpful for figuring out if a fault occurs when the engine is cold, idling, or under load. 

2. Common Codes to Understand and What They Mean

We talked about the pattern, but here are some of the common codes for you to remember. 

  • P0171: This code tells you that the system is running too lean on bank 1. This can indicate a vacuum leak, a dirty airflow sensor, or low fuel pressure. 

  • P0301 to P0304: When you see these codes, you are looking at a misfire in a specific cylinder. You need to check the spark plugs, ignition coils, and injectors. 

  • P0420: This code means the catalyst efficiency is below the threshold on bank 1. This can happen because of a worn catalytic converter, a faulty oxygen sensor, or an exhaust leak. 

Remember, a code points to a symptom and a system, not a specific part that’s at fault. Just because you see P0420 doesn’t mean you need a new converter right away. Always confirm the cause with live data and a thorough inspection before buying anything. 

3. Next Steps After Reading Codes

Once you’ve identified what the code is telling you, follow these steps to diagnose the problem without losing useful information:

  • Don’t clear codes immediately. Clearing the codes will wipe out the freeze frame data and reset the car's readiness monitors. Keep in mind those monitors require a few drive cycles to come back online, so your car might not pass an emissions inspection right after a reset. It's best to fix the issue first, and then clear the codes. 

  • Look up the specific code along with your vehicle model to uncover common issues and their solutions. 

  • Make sure to clear the codes only after you've made the necessary repairs or if a diagnostic flow specifically tells you to do so. 

With the right vehicle scanner and a straightforward approach, OBD2 fault codes become a helpful guide rather than a puzzle.

OBD2 Fault Codes

Conclsion 

Reading OBD2 fault codes with an Autel scanner does not have to be complicated, even if you are new to vehicle diagnostics. The key is understanding what each code means, checking freeze-frame and live data, and confirming the actual cause before replacing parts. 

Whether you need an Autel scan tool for car diagnostics for basic troubleshooting or advanced capabilities such as ECU programming and ADAS System calibration, choosing the right equipment makes a difference. 

For workshops and technicians, Autolines Australia can be a useful source for professional diagnostic equipment. With the right approach, you can find the best car diagnostic scan tool in 2026 for your needs and diagnose faults with greater confidence.

FAQs

1. Can a beginner use an Autel scanner?

Yes, most Autel scanners provide guided menus that make basic code reading straightforward. Beginners should still research codes before attempting repairs.

2. Should I clear an OBD2 code after reading it?

You should generally avoid clearing codes before diagnosing the underlying problem. Keeping the original information can help identify when and under what conditions the fault occurred.

3. Does an OBD2 code identify the exact faulty part?

Not always, because a code usually identifies a system or detected condition rather than a failed component. Additional testing is needed to confirm the actual cause.
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