Technical Description of OBD-II Trouble Code
The circuit for the crankcase pressure sensor is experiencing low voltage.
What does that mean?
This is a generic powertrain diagnostic trouble code (DTC) that is typically found in OBD-II vehicles. This code can apply to various vehicle makes such as Ford, Dodge, Ram, Jeep, Fiat, Nissan, and more.
Among the many sensors that the ECM (Engine Control Module) monitors and adjusts, the crankcase pressure sensor is responsible for providing the ECM with accurate crankcase pressure values. This is important for maintaining a healthy atmosphere within the engine.
Since there are numerous fumes within the engine while it is running, it is crucial for the ECM to have an accurate crankcase pressure value. This value helps prevent pressure from getting too high and potentially causing damage to seals and gaskets. Additionally, the ECM requires this value to recycle burnable fumes back into the engine through the PCV (Positive Crankcase Ventilation) system.
Any unused burnable crankcase fumes are directed into the engine’s intake to be burned. This collectively improves emissions and fuel economy. Therefore, it is important to address any issues related to this fault promptly. Neglecting this fault may lead to gasket failure, o-ring leaks, shaft seal leaks, and other problems. As the name suggests, the sensor is usually mounted on the crankcase.
Code P051C Crankcase Pressure Sensor Circuit Low and related codes are activated by the ECM when it detects that one or multiple electrical values in the crankcase pressure sensor circuit are operating outside the desired range.
When your instrument cluster displays the P051C Crankcase Pressure Sensor Circuit Low code, it means that the ECM has detected a low voltage condition within the crankcase pressure sensor circuit.
Here is an example of a crankcase pressure sensor for a Cummins engine:
What is the severity of this DTC?
In the grand scheme of things, this fault can be considered moderate-low. While immediate drastic further damage is not likely, it is important to address this issue sooner rather than later. As mentioned earlier, neglecting this fault can lead to various problems, so it should not be ignored.
What are some of the symptoms of the code?
Symptoms of a P051C diagnostic code may include:
What are some of the common causes of the code?
Causes for this P051C engine code may include:
What are some P051C diagnostic and troubleshooting steps?
The first step in troubleshooting any malfunction is to research the Technical Service Bulletins (TSB) for known issues with the specific vehicle.
For example, there are known issues with some Ford EcoBoost vehicles and some Dodge/Ram vehicles that have TSBs related to this DTC and/or related codes.
Advanced diagnostic steps will vary depending on the specific vehicle and may require specialized equipment and knowledge. The following are basic steps, but it is recommended to refer to a vehicle year/make/model/powertrain specific repair guide for detailed steps.
Basic Step #1
First, for this fault, it is recommended to open the oil cap on the top of the engine (location may vary) to inspect for any signs of sludge build-up. Sludge can be caused by factors such as infrequent oil changes or longer than recommended intervals between oil changes. It is generally recommended to change conventional oil every 5,000 kilometers and synthetic oil every 8,000 to 10,000 kilometers. However, manufacturer recommendations may vary. A PCV (Positive Crankcase Ventilation) issue can also cause moisture to enter the system and contribute to sludge formation. Ensure that the oil is clean and at the appropriate level.
NOTE: Avoid overfilling the engine with oil. If overfilling occurs, do not start the engine and drain the oil to bring the level within an acceptable range.
Basic Step #2
Test the sensor by following the manufacturer’s specific desired values outlined in the service manual. This typically involves using a multimeter to test different values between pins. Record and compare the findings to the specifications for your make and model. If the values are outside of the specified range, the crankcase pressure sensor should be replaced.
Basic Step #3
Since crankcase pressure sensors are typically mounted directly to the engine block (also known as the crankcase), the harnesses and wires involved are routed through crevices and areas with extreme temperatures (such as the exhaust manifold). When visually inspecting the sensor and circuits, be aware of these factors. The wires and harnesses are exposed to the elements, so check for any hardened or cracked wires or moisture in the harness.
NOTE: Ensure that the connector is securely connected and free of any oil residue.
