Technical Description of OBD-II Trouble Code
The circuit for Fuel Pressure Sensor B is experiencing low levels
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code, which means it applies to OBD-II equipped vehicles that have a fuel pressure sensor (Chevrolet, Ford, GMC, Chrysler, Toyota, etc.). Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle. Anecdotally, this code appears to be more common in GM vehicles (GMC, Chevrolet, etc.) and Dodge/Ram vehicles, and it may be accompanied by a P018B code and/or other codes at the same time.
Most modern vehicles are equipped with a fuel pressure sensor (FPS). The FPS is one of the primary inputs to the powertrain control module (PCM) for controlling the fuel pump and/or fuel injector.
The fuel pressure sensor is a type of sensor known as a transducer. This type of sensor changes its internal resistance in response to pressure. The FPS is typically mounted on either the fuel rail or fuel line. Generally, there are three wires connected to the FPS: reference, signal, and ground. The sensor receives a reference voltage from the PCM (typically 5 volts) and sends back a return signal voltage that corresponds to the fuel pressure.
In the case of this code, the “B” indicates that the problem lies with a portion of the system circuit, rather than a specific symptom or component.
Code P018C is triggered when the PCM detects a low fuel pressure sensor signal. This usually indicates a shorted circuit. Related codes include P018A, P018B, P018D, and P018E.
An example of a fuel pressure sensor:
Code Severity & Symptoms
These codes range in severity from moderate to severe. In some cases, they can result in a vehicle that won’t start. It is advisable to address this code as soon as possible.
Symptoms of a P018C trouble code may include:
Common Causes Of This DTC Code
Possible causes for this code may include:
Diagnostic and Repair Procedures
Begin by checking the fuel pressure sensor and the corresponding wiring. Look for loose connections, damaged wiring, etc. If any damage is found, repair it as necessary, clear the code, and see if it returns. Next, check for any technical service bulletins (TSBs) related to the issue. If nothing is found, you will need to proceed with a step-by-step diagnosis of the system.
The following is a generalized procedure, as testing for this code varies between vehicles. To accurately test the system, you should refer to the manufacturer’s diagnostic flow chart.
Check the wiring
Before proceeding, consult the factory wiring diagrams to determine which wires are which. Autozone offers free online repair manuals for many vehicles, and ALLDATA offers single vehicle subscriptions.
Check the reference voltage portion of the circuit
With the vehicle ignition on, use a digital multimeter set to DC volts to check for reference voltage (usually 5 volts) from the PCM. To do this, connect the negative meter lead to ground and the positive meter lead to the sensor B+ terminal on the harness side of the connector. If no reference signal is present, connect the meter set to ohms (with the ignition off) between the reference voltage pin on the fuel pressure sensor and the reference voltage pin on the PCM. If the meter reads out of limits (OL), there is an open circuit between the PCM and sensor that will need to be located and repaired. If the meter reads a numeric value, there is continuity.
If everything is functioning properly up to this point, you’ll want to check that there is power coming out of the PCM. To do this, turn the ignition on and set the meter to DC volts. Connect the positive meter lead to the reference voltage terminal on the PCM and the negative lead to ground. If there is no reference voltage from the PCM, the PCM is likely faulty. However, PCMs rarely go bad, so it’s a good idea to double-check your work up to this point.
Check the ground portion of the circuit
With the vehicle ignition off, use a digital multimeter set to ohms to check for continuity to ground. Connect the meter between the fuel pressure sensor connector ground terminal and chassis ground. If the meter reads a numeric value, there is continuity. If the meter reads out of limits (OL), there is an open circuit between the PCM and sensor that will need to be located and repaired.
Check the return signal portion of the circuit
Turn the vehicle ignition off and turn your multimeter to the ohms setting. Connect one meter lead to the return signal terminal on the PCM and the other to the return terminal on the sensor connector. If the meter displays out of limits (OL), there is an open circuit between the PCM and sensor that must be repaired. If the meter reads a numeric value, there is continuity.
Check the fuel pressure sensor reading against actual fuel pressure
The testing done up to this point indicates that the fuel pressure sensor circuit is functioning properly. Next, you’ll want to check the sensor itself against the actual fuel pressure. To do this, start by attaching a mechanical fuel pressure gauge to the fuel rail. Next, connect a scan tool to the vehicle and select the FPS data parameter for viewing. Start the engine while simultaneously viewing both the actual fuel pressure and the FPS sensor data on the scan tool. If the readings are not within a couple of psi of one another, the sensor is faulty and should be replaced. If both readings are below the manufacturer’s fuel pressure specifications, the FPS is not to blame. Instead, there is likely a fuel delivery problem, such as a failed fuel pump, that will require diagnosis and repair.
