How to Use a Code Reader on a Vehicle

auto code reader

You ordered a fantastic code reader, which was the first step to being ahead of your mechanic regarding your vehicle's maintenance. The only remaining step is learning how to use the code reader.

Using the tool is quite simple, and there’s always a manual to guide you through the process. However, if you lost your user manual, you are on the right platform. We will guide you on how to use a code reader on your vehicle.

What You Need

Diagnosing the problematic issues in your car is easy. You might also need high-level mechanic skills and specialized tools, which you only find in a repair shop. What you should never take a chance with is the trial-and-error process that comes about when fixing a car. You have probably been in a situation where you want to repair your car, but you don’t know where there could be a problem.

That’s where the code reader comes through. It only makes sense that it should be the first thing you should have. This tool can read the diagnostic trouble codes and help you understand the problem under your hood. The other crucial thing you need is the OBD2 port. The port is available in post-1996 cars.

The Process of Using a Code Reader

Most cars on the road today were manufactured in the 21st century. Many more are coming, and the current ones use a diagnostic link connector known as OBD2. We are going to show you the process of reading these codes.

Step 1: Find the OBD2 Port

Most cars, if not all, have an OBD2 port. For sure, all the American, European, and Asian popular brands have it. The only difference is where the port is situated in your car. The 16-pin connector is located on the left side of the dash, near the steering wheel. It’s usually covered with a flap or door.

The port can also be located under the passenger side or in the center column of your car. If you still can’t find your OBD2 port, search on the web. Type your car’s model and year, and you’ll get the answer. If you still have your car’s owner’s manual, you can use it to find the port.

Step 2: Connect Your OBD2 Code Reader

Assuming that you have found where the OBD2 is, the next step is connecting the code reader to your car’s computer. The code reader either comes with a connector cable or as a Bluetooth module. Both have a 16-male pin plug that goes into the port.

Once you insert it, check the code reader’s instructions in the manual. Does it turn on from its own battery, or you must turn on the car's ignition to idle mode? Will it work after your turn on the engine? All those answers are in the manual.

Step 3: Turn the Ignition On

Most code readers require you to turn the ignition to idle mode without starting your engine. The screen of the code reader will light up, which means that the tool has been powered. A message will appear on the screen.

If the screen doesn’t light up, the connection was unsuccessful. Jiggle the plug a bit. If it doesn’t work, try and see if the cigarette lighter works. If it doesn’t, the OBD2 system’s fuse is damaged, and the circuit has no power. Locate the fuse and try to resolve the issue.

Step 4: Enter the Vehicle Information

Some scanners will require you to enter the vehicle identification number. Every vehicle has a unique VIN. You’ll also be requested to enter information about the make and model and specify your engine type.

A more advanced code reader will not ask for these details but read them by itself. If it does ask for the VIN, however, you can find the sticker of the VIN on the lower corner of the windshield on the left. It can also be under the hood or at the front of the vehicle frame.

Step 5: Get the Codes

Once you enter the information, the scanner will pick the DTCs from your computer and show them on the scanner, and if you use a Bluetooth-enabled module, the codes will be displayed on your phone or tablet.

The code reader will read active and pending codes. The active codes are responsible for the check engine light. If a pending code occurs for the second time, it also triggers the check engine light. Pending codes indicate that the emission control system has issues. Some code readers reveal all the trouble codes, while others let you choose the codes you want to read.

Step 6: Identifying and Interpreting the Codes

Some code readers will only show you codes, while some offer a brief explanation. More advanced ones explain them deeply. If your code reader requires you to interpret the codes, here’s how to do it.

The trouble codes come in 4 figures. Th first one is a letter indicating the vehicle's system with the issue, while the numbers indicate the exact area with the fault issue. The letters can be;

  • P: This indicates powertrain issues on either the engine, ignition, transmission, emission, or fuel system.
  • B: If a code starts with “B,” it signifies an issue in the body. It can be with seatbelts, airbags, or power steering.
  • C: This implies there’s a chassis issue. It could be axles, brakes, the braking system, and brake fluid.
  • U: Meaning undefined, a code that starts with “U” highlights issues not specified for P, B, or C.

The set of numbers in the fault code also have a meaning. Here’s how they arrange themselves;

  • First digit: The number that follows the letter signifies whether the diagnostic trouble code is generic-specific (0) or manufacturer-specific.
  • Second digit: The vehicle part with the issue.
  • Last two digits: The exact problem.

Find out what the error codes mean through the internet. Once you do, reset the check engine light and head to your mechanic.


A code reader will help you identify the issues affecting your car, but it won’t resolve the problem. To determine the issue, you must repair and maintain the affected parts or visit the mechanic. If you’re looking to buy a code scanner, check out the Ancel website, and you’ll find the right scanner.

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