Technical Description of OBD-II Trouble Code
Circuit B of the Fuel Pressure Sensor
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to OBD-II equipped vehicles with a fuel pressure sensor (Ford, Chevrolet, Chrysler, Toyota, etc.). Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
Most modern vehicles are equipped with a fuel pressure sensor (FPS). The FPS is an important input 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 based on pressure. The FPS is usually mounted on either the fuel rail or fuel line. Typically, there are three wires connected to the FPS: reference, signal, and ground. The sensor receives a reference voltage from the PCM (usually 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 is with a portion of the system circuit, rather than a specific symptom or component.
Code P018A is triggered when the PCM detects a malfunction in the fuel pressure sensor circuit. Related codes include P018B, P018C, P018D, and P018E.
An example of a fuel pressure sensor:
Code Severity & Symptoms
These codes have a moderate to severe severity level. In some cases, they can cause a vehicle to not start. It is recommended to address this code as soon as possible.
Symptoms of a P018A 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 check if it returns. Next, check for any technical service bulletins (TSBs) related to the issue. If no TSBs are found, proceed with step-by-step diagnosis of the system.
The following is a general procedure, as the testing for this code varies between vehicles. To accurately test the system, refer to the manufacturer’s diagnostic flow chart.
Check the wiring
Before proceeding, consult the factory wiring diagrams to determine the identification of the wires. 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 the 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 needs to be located and repaired. If the meter reads a numeric value, there is continuity.
If everything is functioning properly up to this point, 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 is advisable to double-check the work done 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 needs to be located and repaired.
Check the return signal portion of the circuit
Turn the vehicle ignition off and set the 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 the actual fuel pressure
The testing done up to this point indicates that the fuel pressure sensor circuit is functioning properly. Next, check the sensor itself against the actual fuel pressure. Start by attaching a mechanical fuel pressure gauge to the fuel rail. Then, 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 each other, 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.
