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Nothing is more concerning for drivers than when the dreaded check engine light illuminates on the dashboard. This warning signals potential issues with the engine or other vital systems like the transmission. However, with the right knowledge and tools, understanding and decoding OBD-II engine trouble codes can empower drivers to address issues promptly and effectively.
What Are OBD2 Codes?
When the check engine light activates, it indicates a problem detected by the vehicle's ECU (Engine Control Unit). Instead of displaying specific check engine light codes directly on the dashboard, the check engine light serves as a general alert. However, with an OBD-II reader, drivers can retrieve and interpret the exact trouble code, providing valuable insight into the underlying issue.
Most Common OBD-II Engine Trouble Codes to Look out For
The most prevalent OBD2 codes typically fall within the "P" range, which pertains to the powertrain. These check engine codes commonly relate to engine, transmission, or exhaust system problems. Among them, "P0300" stands out as one of the most frequent, indicating a cylinder misfire. Other common codes include:
- P0128: Coolant thermostat (too low)
- P0171 and P0174: Engine running lean
- P0401: Exhaust gas recirculation (EGR) flow insufficient
- P0442: EVAP system emissions leak
- P0300: Cylinder misfire
- P0446 Evaporative Emission Canister Vent Solenoid
Common OBD-II Engine Trouble Code B Range
Codes in the B-range refer to issues within the vehicle's body, encompassing safety and comfort features. Notable examples include:
B0081 First Row Center Seatbelt Load Limiter Deployment Control
Every vehicle has to have a restraint system that goes above and beyond the scope of a seatbelt, which is usually the airbags. The code B0081 refers to the passenger presence system, which activates when someone isn't heavy enough to be an adult because an airbag will injure a small child.
Aside from a "Check Engine" light, you may notice the airbag light for the passenger seat will not be on. Problems that will trigger this code include sensors in the seat not working, wiring harness problems, and the on/off indicator not working.
B0028 Right Side Airbag Deployment Control (Subfault)
One of the most common B-range codes is B0028, which stands for Right Front Passenger Side Deployment Loop Resistance Low, which is part of the Supplemental Restraint System (SRS). While that sounds daunting, it typically refers to an issue with the airbag. Every vehicle is required to have an SRS, which assists with seat belts and other protective measures.
When you see this trouble code, it usually means that there is an issue with the airbag, a sensor that connects to the airbag, or a voltage problem.
Common OBD-II Engine Trouble Code C Range
The C-range of codes concerns the vehicle's chassis, covering steering, braking, ABS sensors, and suspension. Common examples include:
C0221 Wheel Speed Sensor Code
One of the most common C-range codes is the wheel speed sensor code, which is C0221. This code means that you have a problem with the front wheel speed sensor on your right wheel. Sensors for wheel speed are connected to the anti-lock brake system that modern vehicles have, otherwise known as ABS.
When you see this code, it will be accompanied by the ABS light, "Check Engine" light, or both. Usually, it's a faulty sensor or a bad connection, but it's important to have the issue addressed because your tires might lock up and slide on wet surfaces.
C0045 Brake Pressure Sensor
OBD-II code C0045 will appear when your vehicle's brake pressure sensor is having problems. This can be anything that's not up to OEM standards, which will vary based on the manufacturer. These sensors are important for vehicle function, and this code will usually be accompanied by a "Check Engine" or ABS light on the dashboard.
Symptoms of this code may be problems with your vehicle's wheel speed or brakes. You may even experience locked brakes if the issue spreads to your anti-lock brake system.
Common OBD-II Engine Trouble Code P Range
The P-range is extensive and encompasses various powertrain issues. Some notable codes include:
P0446 Evaporative Emission Canister Vent Solenoid
Your vehicle's EVAP system is one of the most common areas to generate an error code. It's responsible for trapping exhaust vapors and circulating them back through the engine. That said, the P0446 refers to an issue with the evaporative emission canister vent solenoid.
The first thing you'll notice is a "Check Engine" light and some other minor symptoms. Unfortunately, it's not always easy to know where the leak is coming from because the fuel system could be clogged with debris in several locations. However, you may notice the smell of gasoline in some cases.
P0300 Misfire
One of the most common OBD II codes is the P0300 code. It signifies a misfire from one of your engine's cylinders. Usually, this code means that more than one of your engine's cylinders is misfiring. You'll notice a "Check Engine" light that's followed by a choppy engine that seems to fluctuate at idle, and your steering wheel might shake. Anything that has to do with faulty combustion can result in significant damage if not addressed.
Several issues will trigger a P0300 trouble code. It can be an issue with your fuel system, a clogged fuel injector, or a vacuum leak. Fuel pressure regulators and other components will also lead to a "Check Engine" light and P0300 code.
Common OBD-II Engine Trouble Code U Range
U-range codes relate to communication problems within the vehicle's network. Examples include:
U0121 Loss of Communication Between the ECU and the Anti-Lock Brake System (ABS)
The most common U-range OBD-II code is U0121, which represents a loss of communication between the ECU and the anti-lock brake system (ABS). Vehicles use ABS to prevent wheels from locking if you slam on the brakes, which will save you from sliding across the road in wet conditions.
When the code U0121 displays, you may have issues with your anti-lock brake system. Symptoms will include performance problems with your brakes and an ABS warning light. This problem is typically caused by a faulty ABS module or a dead battery.
U0107 Lost Communication With Throttle Actuator Control Module
The trouble code U0107 is common among vehicles with electronic throttle bodies, which you won't find in older vehicles. This electronic throttle body controls components like a motor that opens or closes the throttle blade(s), throttle position sensors, and an electronic throttle actuator. When this code appears, it means that your vehicle's ECU is having trouble communicating with this component.
A handful of symptoms will be accompanied by this code. These include performance issues with the throttle and several warning lights like the "Check Engine" light. This code can be caused by battery problems, a problem with any TAC circuits, and a problem with the CAN bus.
Other Common OBD-II Engine Trouble Codes
Beyond the aforementioned categories, numerous other OBD-II trouble codes exist, covering a wide range of systems and components in vehicles. Drivers should be aware that their vehicle may encounter additional codes not covered here. In such cases, using an OBD-II reader can provide valuable diagnostic information for effective troubleshooting.
Understanding OBD2 codes and their meanings empowers drivers to address vehicle issues promptly, potentially saving time and money on repairs. Whether it's a powertrain, body, chassis, or network-related code, early diagnosis and intervention are key to maintaining vehicle performance and safety. For reliable guidance and quality automotive parts, drivers can turn to trusted resources like JEGS. Stay informed, drive safely, and keep your vehicle running smoothly.
