You are enjoying a nice drive and suddenly the most mysterious light comes on: "Check engine". What does it mean? The engine is a very large and complex system, so "checking the engine" often doesn't give you the answers you are looking for. This is where the OBD-II code reader comes into play. This small tool allows you to accurately identify the source of the error.
Steps
Part 1 of 2: Get the Codes
Step 1. Get an OBD-II scan tool
You can find them on the internet and in many auto parts stores. If you have a smartphone with Bluetooth, you can download an app that can interpret the data and purchase an OBD reader that displays the codes and explanations directly on the mobile.
- If your car was built before 1996 you must purchase an OBD-I scanner specific to your vehicle and not use the universal OBD-II code system. This article only deals with the OBD-II system.
- The OBD-II system constantly monitors the performance of the engine and the emission control system. The Check Engine Light comes on when a malfunction occurs that causes the car to produce a quantity of emissions equal to 150% of the maximum permitted by law.
Step 2. Find your vehicle's Diagnostic Link Connector (DLC)
This is a triangular shaped 16-pin connector, usually found on the left side of the dashboard, near the steering wheel. If you can't find it, search the internet for its location using your car's model and year of manufacture, or in the manual.
Step 3. Insert the scan tool or code reader connector into the DLC
Turn the key, but don't start the engine. The scanner will start communicating with the car's on-board computer. Messages such as "searching for protocol" and "establishing data transmission link" may appear.
- If the screen goes blank and does not turn on, move the connector so that the contact between the scanner and the pins is better. Older cars often have connection difficulties.
- If you still can't get the device to work, make sure the cigarette lighter is working. The OBD-II system, in fact, uses the cigarette lighter circuit as a power supply. If the cigarette lighter doesn't work, find and replace the corresponding fuse.
Step 4. Enter the vehicle information
On some scanners, you need to enter the chassis number as well as the make, model and in some cases the car engine. The operation varies by device.
Step 5. Find the menu
When the scanner starts up, it looks for a menu. Select "Codes" or "Trouble Codes" to open the main code menu. Depending on the device and vehicle year of manufacture, you may see some options, such as Engine / Powertrain, Transmission, Airbag, Brakes, etc. Choose one and you will see two or more types of codes. The most common ones are the active ones and the pending ones.
- Active codes are constant malfunctions that cause the Check Engine Light to come on. Just because the light is off does not mean that the fault is gone, it simply means that the code detection conditions for two or more vehicle operations have not been met.
- Pending codes indicate that the OBD-II control system has detected a problem with the emission control system and that if the fault recurs it will become an active code and the Check Engine Light will illuminate.
Part 2 of 2: Understanding the Codes
Step 1. Learn the meaning of the letters
Codes begin with a letter indicating which system they refer to. You can find several letters, although you have to navigate through the various menus to see them:
- P. - Powertrain. This is the largest set of codes, covering the engine, transmission, fuel system, ignition, emissions and more.
- B. - Body. These codes indicate problems with airbags, seat belts, seat checks, and more.
- C. - Chassis. These codes cover ABS, brake fluid, axles, and more.
- U - Undefined. These codes deal with other elements of the car.
Step 2. Learn the meaning of the numbers
P0xxx, P2xxx and P3xxx are generic codes that apply to all makes and models. The P1xxx codes are specific to each manufacturer, such as Fiat, Ford, Toyota, etc. The second number indicates which subsystem the code refers to. For example, the P07xx codes signal problems with the transmission.
The last two digits represent the specific problem indicated by the code. Consult a table on the internet for more details on each code
Step 3. Read an example code
P0301 indicates a misfire problem in number 1 cylinder. The P indicates that the code refers to the powertrain (powertrain), the 0 being a generic or universal code. The 3 indicates that the problem is related to the ignition subsystem.
- 01 indicates that it is a problem with the cylinders, in particular a misfire in the number 1 cylinder. cylinder.
- The codes do not indicate which components are faulty, only that there is a malfunction in a component, its circuits or the systems that control it. The code can be a symptom of a failure caused by a completely different system.
Step 4. Diagnose your vehicle
Making a correct diagnosis of OBD-II codes takes years of training and practice. For example, if the battery is low or the alternator is worn out, five or more codes may appear in fully functional systems. Before attempting the repair, you must understand that the codes alone do not reveal which parts need to be replaced or where to intervene.
If you're not sure what to do, take your car to a professional mechanic, otherwise you could end up wasting a lot of time and money
Step 5. Reset the Check Engine Light
If you have completed the repairs or just if the warning light is bothering you, you can reset it with almost any OBD scanner. The light will not come on again for a certain period of time (depending on the manufacturer).
You can reset the Check Engine light from the main menu of most scanners. In some cases it is referred to as CEL
Advice
A code reader offers limited functionality to reading and clearing codes. It does not provide real-time data and does not indicate which diagnostic tests failed or which completed successfully. Scanning devices, which are more expensive and difficult to use, are able to read codes, provide specific malfunction details, read and view real-time data, as well as help confirm diagnoses
Warnings
- Remember that the codes do not indicate which parts to replace. If in doubt, consult a professional mechanic.
- After repairs, you have to drive the car for a full cycle in order to reset all detectors. If necessary, perform an emissions test as well.
