P018B Fuel Pressure Sensor Circuit Performance Range B

P018B Fuel Pressure Sensor Circuit Performance Range B

OBD-II DTC Datasheet

Fuel Pressure Sensor B Circuit Out of Range / Performance

What does this mean?

This Diagnostic Trouble Code (DTC) is a generic transmission code, which means it applies to OBD-II equipped vehicles with a fuel pressure sensor (Chevrolet, Ford, GMC, Chrysler, Toyota, etc.). Although it is general, the exact repair steps may vary depending on the make / model. Ironically, this code seems to be much more common on GM vehicles (GMC, Chevrolet, etc.) and may be accompanied by a P018C code and / or other codes at the same time.

Most modern vehicles are equipped with a fuel pressure sensor (FPS). FPS is one of the main inputs to the powertrain control module (PCM) to control the fuel pump and / or fuel injector.

The fuel pressure sensor is a type of sensor called a transducer. This type of sensor changes its internal resistance with pressure. The FPS is usually mounted to either the fuel rail or the fuel line. Usually there are three wires going to the FPS: reference, signal and ground. The sensor receives a reference voltage from the PCM (usually 5 volts) and sends back a feedback voltage that corresponds to the fuel pressure.

In the case of this code, "B" indicates that the problem is with a portion of the system chain and not with a specific symptom or component.

P018B is set when the PCM detects a performance problem with the fuel pressure sensor. Associated codes include P018A, P018C, P018D, and P018E.

Fuel pressure sensor example:

Code severity and symptoms

The severity of these codes is moderate to severe. In some cases, these codes can cause the car to not start. It is recommended to fix this code as soon as possible.

Symptoms of a P018B trouble code may include:

• Check Engine Light
• Engine that is difficult to start or won't start
• Poor engine performance

Common Causes of This DTC

Possible reasons for this code could include:

• Defective fuel pressure sensor
• Fuel delivery problems
• Wiring problems
• Defective PCM

Diagnostic and repair procedures

Start by checking the fuel pressure sensor and associated wiring. Look for loose connections, damaged wiring, etc. If damage is found, repair as needed, clear the code and see if it returns. Then check the technical service bulletins (TSBs) for the problem. If nothing is found, you will need to proceed to the step-by-step system diagnostics.

The following is a generalized procedure as the testing of this code differs from vehicle to vehicle. To accurately test the system, you need to refer to the manufacturer's diagnostic flowchart.

Check wiring

Before proceeding, you need to consult the factory wiring diagrams to determine which wires are which. Autozone offers free online repair guides for many vehicles and ALLDATA offers a one-car subscription.

Check part of the reference voltage circuit.

With the vehicle ignition on, use a digital multimeter set to DC voltage to check 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 B+ sensor terminal on the harness side of the connector. If there is no reference signal, connect a meter set to ohms (ignition OFF) between the reference voltage terminal on the fuel pressure sensor and the reference voltage terminal on the PCM. If the meter reading is out of tolerance (OL), there is an open circuit between the PCM and the sensor that needs to be located and repaired. If the counter reads a numeric value, there is continuity.

If everything is fine up to this point, you will want to check if power is coming out of the PCM. To do this, turn on the ignition and set the meter to constant voltage. Connect the meter positive lead to the PCM reference voltage terminal and the negative lead to ground. If there is no reference voltage from the PCM, the PCM is probably faulty. However, PCMs rarely fail, so it's a good idea to double check your work up to that point.

Check the grounding part of the circuit.

With the vehicle ignition OFF, use a resistor DMM to test the continuity to ground. Connect a meter between the ground terminal of the fuel pressure sensor connector and chassis ground. If the counter reads a numeric value, there is continuity. If the meter reading is out of tolerance (OL), there is an open circuit between the PCM and the sensor that needs to be located and repaired.

Check part of the return signal circuit.

Turn off the car ignition and set the resistance value on the multimeter. Connect one test lead to the return signal terminal on the PCM and the other to the return terminal on the sensor connector. If the indicator shows out of range (OL), there is an open circuit between the PCM and the sensor that needs to be repaired. If the counter reads a numeric value, there is continuity.

Compare the fuel pressure sensor reading with the actual fuel pressure.

Testing performed up to this point shows that the fuel pressure sensor circuit is OK. Then you will want to test the sensor itself against the actual fuel pressure. To do this, first attach a mechanical pressure gauge to the fuel rail. Then connect the scan tool to the vehicle and select the FPS data option to view. Start the engine while viewing the scan tool actual fuel pressure and FPS sensor data. If the reading is not within a few psi of each other, the sensor is defective and should be replaced. If both readings are below the manufacturer's specified fuel pressure, the FPS is not at fault. Instead, there is likely to be a fuel supply problem such as a failed fuel pump that will require diagnosis and repair.

Related DTC discussions

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