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5 Most Common Car Trouble Codes

5 Most Common Car Trouble Codes

Unfortunately, we have all been there. Driving down the road and out of the blue, the check engine light illuminates. There’s something wrong with the car, but the real question is – What’s wrong with it? Before you take your car to the local auto repair center, bear in mind that the computer is telling you that something must be inspected. A mechanic will perform a diagnostic test, using a scan tool, to determine what’s the problem.

On-Board Diagnostics (OBD-II) represents an automotive term that refers to the vehicle’s self-diagnostic and reporting capability. When the check engine light is on, this means that your car has at least one, or event more OBD-II trouble codes.

Back in 1966, the strict smog emission control standards, initiated by the state of California, led to the creation of these OBD systems for cars to implement emissions control systems. In 1968, the federal government expanded these controls across the country. The purpose of the OBD-II is to detect a problem with your vehicle that could cause its emissions to exceed 1.5 times the allowed limit.

The diagnostic code, or trouble code, is, in fact, an alphanumeric value that corresponds to a specific problem. The codes were created by the Society of Automotive Engineers (SAE) to comply with OBD-II emissions regulations in the US.

The trouble codes are separated into 4 categories: Network Communications (U), Chassis ©, Body (B), and Powertrain (P). Furthermore, the codes are divided into 2 major groups: enhanced or manufacturer specific (1 as the second digit) and generic or global (0 as the second digit).

Here are the 5 most common car trouble codes you’ll likely experience at some point.

1. Evaporative System

CODES: P0411, P0440, P0442, P0446, P0455

The main purpose of the evaporation system (EVAP) is to contain and remove vapors that are produced by the burnt fuel. A loose gas cap enabling fuel vapors to get away from the fuel tank is usually a good reason for setting off the trouble code. EVAP consists of a charcoal canister, vent hoses, a pressure or vacuum sensor, and a purge valve.

2. Catalytic Converter

CODE: P0420, P0430

The catalytic converter is monitored by the downstream oxygen sensor. The main purpose of the catalytic converter is to convert the toxic pollutants and gases in exhaust gas to less toxic pollutants by catalyzing a redox reaction. If the engine is worn out, leaks coolant internally, or burns oil, this could result in the contamination of the converter and the increase of the tailpipe emissions.

3. Oxygen Sensor

CODES: PO171-P0175

Another common car problem includes a faulty oxygen sensor. This sensor monitors the oxygen’s amount in the exhaust so the engine computer can adjust the fuel mixture to minimize emissions and maximize fuel economy. If there’s a problem with the oxygen sensor, your mileage will increase significantly and there’s a chance that your car will stall.

4. Engine Misfire

CODES: P0300-P0305

Auto mechanics regularly work on engine misfires. If your car’s engine is suffering from misfiring, this means that one of the cylinders or more is not working the right way. While idling, if your car is shaking or vibrating, this means that your car is not as fuel-efficient as it should be, and this is an indicator that you might be experiencing an engine misfire problem. The OBD-II system tracks engine misfires by monitoring the crankshaft’s speed when the engine is working. When the OBD-II system detects a minimal loss of speed in the crankshaft, it logs a misfire.

5. Exhaust Gas Recirculation (EGR)

CODE: P0401

The exhaust gas recirculation, popularly known as EGR, regulates the engine’s emission of smog-causing nitrous oxides (NOx). The purpose of the EGR is to recirculate part of the exhaust gas of the engine back to the engine cylinders. Тhe computer system of the car opens and closes valves to recirculate the exhaust gas of the engine. If the car takes a lot of short trips or the oil hasn’t been changed in a while, problems are bound to happen, because the car doesn’t have the required time to warm up, resulting in carbon buildup.

The next time you notice an illuminating check engine light, you’ll have more confidence knowing that it’s probably one of the listed car trouble codes, above. Get your car serviced at a certified auto repair facility and make sure your car is running smoothly and not polluting the environment.


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