Technical Description of OBD-II Trouble Code
The circuit for the crankcase pressure sensor is registering a high reading.
What does that mean?
This is a standard diagnostic trouble code (DTC) for powertrain issues in OBD-II vehicles. This code can apply to various vehicle makes such as Ford, Dodge, Ram, Jeep, Fiat, Nissan, etc.
Among the many sensors that the Engine Control Module (ECM) monitors and adjusts, the crankcase pressure sensor is responsible for providing the ECM with accurate crankcase pressure values. This is crucial for maintaining a healthy atmosphere within the engine.
Since the engine produces a significant amount of fumes while running, it is important for the ECM to have precise crankcase pressure values. This helps prevent pressure from getting too high and potentially damaging seals and gaskets. Additionally, the ECM requires this value to recycle burnable fumes back into the engine through the Positive Crankcase Ventilation (PCV) system.
Any unused burnable crankcase fumes are directed into the engine’s intake to be burned, which improves emissions and fuel economy. Therefore, it is essential 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 typically mounted on the crankcase.
Code P051D Crankcase Pressure Sensor Circuit High and related codes are activated by the ECM when it detects that one or more electrical values in the crankcase pressure sensor circuit are operating outside the desired range.
When your instrument cluster displays the P051D Crankcase Pressure Sensor Circuit High code, it means that the ECM has detected a high 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 unlikely, it is important to address this issue sooner rather than later. As mentioned earlier, neglecting this fault can lead to various potential issues, so it is crucial to keep them in mind.
What are some of the symptoms of the code?
Symptoms of a P051D diagnostic code may include:
What are some of the common causes of the code?
Possible causes for this P051D engine code may include:
What are some diagnostic and troubleshooting steps for P051D?
The first step in troubleshooting any malfunction is to research the Technical Service Bulletins (TSB) for known issues with your 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 similar 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-specific repair guide for detailed instructions.
Basic Step #1
First, for this fault, it is recommended to open the oil cap on the top of the engine (location may vary) and inspect for any signs of sludge build-up. Sludge can be caused by factors such as infrequent oil changes or longer-than-recommended intervals. 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 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 specified values in your service manual. This typically involves using a multimeter to test different values between pins. Record and compare the findings with the specifications for your make and model. If the values are outside the specified range, the crankcase pressure sensor should be replaced.
Basic Step #3
Since crankcase pressure sensors are usually mounted directly on the engine block (crankcase), the harnesses and wires involved are routed through crevices and areas with extreme temperatures (e.g., exhaust manifold). When visually inspecting the sensor and circuits, be aware of this. 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.
