Your check engine light can turn on for various reasons, making it difficult to understand what’s really wrong with your vehicle.
However, don’t worry.
This is when you can turn to check engine codes because they’ll help narrow down the exact issue.
But how do you interpret each check engine light code?
This Article Contains:
- How To Extract Check Engine Codes? (Step-By-Step)
- Common Diagnostic Trouble Codes For Check Engine Lights
- 3 FAQs On Check Engine Codes
How To Extract Check Engine Codes? (Step-By-Step)
Your check engine light turns on when your OBD system (onboard diagnostics) detects an issue or some malfunction.
However, to figure out why your check engine light is illuminated, you need to extract and read the generated diagnostic trouble code or codes (DTC). To do so, you require an OBD scan tool or code reader that you can connect to the OBD port.
Depending on your OBD scanner type, the scan tool will:
- Provide one-liner definitions of the check engine codes (OBD2 scanner).
- Or just display a diagnostic trouble code that’s five-character long (code reader).
Now let’s learn how to extract check engine codes with a scanner:
- Step 1: Find your car’s OBD port (OBD-II diagnostic connector). You’ll mostly find your OBD port under the dashboard on the driver’s side, near the pedals. To connect the scanner or code reader to the port, you’ll need a 16-pin connector.
- Step 2: Now plug one end of the connector to the OBD port or diagnostic connector and the other into your scan tool. The scan tool will switch on as soon as it’s plugged in. If it doesn’t, turn on the ignition to power it.
- Step 3: With the scanner on, you can read the check engine codes on the computer. Follow the user instructions of your scan tool on how to operate it. It’ll mostly ask you to navigate to “Read Codes” and select it.
- Step 4: Note each DTC code your scanner displays. If there are many check engine codes, the scanner or scan tool will cycle through them, or you’ll have the option to press a button to view one trouble code after the other.
With the check engine light code extraction instructions in mind, let’s also go through some check engine light codes.
Common Diagnostic Trouble Codes For Check Engine Lights
Knowing every diagnostic trouble code seems impossible. But there are some you can get familiar with to help you understand your car’s issues better.
Here are some of the most common check engine light diagnostic trouble codes:
A. P0100-P0199: Fuel And Air Metering
The diagnostic codes P0100-P0199 alert vehicle owners about fuel and air metering as well as their car’s oxygen levels. Here are some of their short descriptions:
- P0171: Fuel system of the vehicle is too lean (the air fuel mixture has either too little or too much air)
- P0172: Fuel system is rich (excessive gasoline and insufficient oxygen in the air fuel mixture)
- P0173: Triggered by the engine control module when the air to fuel ratio is either too lean or rich
- P0174: Underreporting in your mass Airflow sensor (MAF sensor reporting very little air in the air fuel mixture
- P0130: O2 sensor or oxygen sensor circuit malfunction (Bank 1, sensor 1). Triggered when there’s no oxygen sensor activity detected
- P0131: Triggered when the ECU (Electronic Control Unit) detects improper voltage from the O2 sensor (O2 sensor circuit low voltage in Bank 1, sensor 1)
- P0133: O2 sensor isn’t changing its voltage output quickly enough to the changing air-fuel ratio (Bank 1, sensor 1)
B. P0200-P0299: Fuel And Air Metering (Fuel Injector Circuit)
Codes P0200-P0299 deal with fuel and air metering (fuel injector circuit). Here are some of the error code meanings:
- P0200: Fuel injector Circuit Malfunction
- P0201: Fuel injector Circuit Malfunction (Cylinder 1)
C. P0300-P0399: Ignition System And Misfire
Codes P0300-P0399 indicate engine misfire or issues with the ignition system. Here are the descriptions of some of them:
- P0300: Engine misfire related to multiple cylinders
- P0301: Engine misfire in cylinder 1
- P0302: Engine misfire in cylinder 2
- P0303: Engine misfire in cylinder 3
- P0351: Fault in ignition coil A or an ignition coil circuit malfunction
- P0352: Fault in ignition coil B or an ignition coil circuit malfunction
D. P0420, P0430: Catalytic Converter
Fault code P0420, as well as code P0430, are associated with the catalytic converter. Here’s what they mean:
- P0420: Catalytic converter isn’t working at its best performance, or there’s a faulty oxygen sensor
- P0430: Problem in the catalyst system (general trouble code often seen with misfire and oxygen sensor codes)
Now that you know how to extract check engine codes with a code reader or OBD scanner and are familiar with some common codes, let’s answer a few FAQs.
3 FAQs On Check Engine Codes
Here are some commonly asked check engine light questions with answers:
1. What Causes My Check Engine Light To Come On?
Your check engine light can light up for a variety of reasons.
Here are some common reasons why your OBD system may generate a diagnostic code and light up the check engine light:
- Missing, damaged, or loose gas cap (the P0457 DTC code implies loose or open gas cap)
- Failing oxygen sensor that needs a replacement
- Faulty spark plug or spark plug wire
- Mass Airflow Sensor (MAF sensor) needs a replacement
- A failed catalytic converter that needs replacing
2. Can I Drive With The Check Engine Light On?
If your check engine light comes on while you’re on the move, don’t panic.
Check if your vehicle is behaving any differently from usual.
For example, did your fuel economy drop even though you just filled your fuel tank?
Then you mostly need to get your oxygen sensor checked.
However, if everything seems normal, you can keep driving.
However, it’s highly recommended to get your vehicle checked by a mechanic as soon as you can.
If the check engine light isn’t just illuminated but is flashing, you should pull over right away. A flashing check engine light is an indication of major damage or malfunction.
That’s because a flashing check engine light typically implies your engine is misfiring. A misfire can harm your engine or catalytic converter.
3. How To Interpret An OBD Code?
An OBD code or diagnostic code is quite easy to understand. Just break down your trouble code into 4 sections.
A. Section One
The first character of the diagnostic trouble code is always a letter.
It can be:
- P: Stands for powertrain
- B: Stands for body
- C: Stands for chassis
- U: Stands for network communications
B. Section Two
The second section of an engine code consists of the next character, a single digit.
It can be:
- 0: denotes a generic code set by the Society of Automotive Engineers (SAE)
- 1: denotes a vehicle manufacturer-specific code (a vehicle manufacturer can add model-specific DTC codes to the list of generic codes)
C: Section Three
The third section in a check engine code includes the third character, which can be a digit between 0 to 9.
- 1: Indicates a fuel or air metering system problem. For example, an issue with the mass airflow sensor (MAF sensor).
- 2: Denotes fuel or air metering systems problems. For example, a fuel injector issue
- 3: Indicates an ignition problem. For example, an engine misfire or ignition coil fault like DTC code P0353.
- 4: Indicates issues with the emissions systems. For example, a catalytic converter efficiency problem.
- 5: Denotes vehicle speed controls and idle control system issues like DTC code P0571 (this error code indicates cruise control/brake switch A circuit malfunction).
- 6: Indicates computer output circuit issues. For example, an internal computer failure.
- 7, 8, or 9: Denote transmission problems. For example, incorrect pressure and sensor failures.
D: Section Four
The fourth section consists of both the fourth and fifth characters (digits). They can be anything between 00 to 99.
These two numbers in an OBD code describe the fault code.
However, there are tons of fault codes. So, to understand the issues, you’ll have to go online and find an OBD code or check engine code interpretation website or contact your mechanic for help.
You can also refer to your owner’s manual provided by the vehicle manufacturer.
Check engine codes are your saviors. They help you pinpoint a problem when something goes wrong with your vehicle, even if it’s just a loose gas cap.
Now that you know how to extract and interpret check engine codes, all you need is a trustworthy mechanic to fix your issues.
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