Technical Description of OBD-II Trouble Code
Frequent Activation of Fuel System Over Pressure Relief Valve
What does that signify?
This is a generic diagnostic trouble code (DTC) for powertrain and is applicable to OBD-II vehicles. This includes vehicles from various manufacturers such as Dodge, Toyota, Ford, Honda, Chevrolet, Ram, etc. Although it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration.
If your vehicle has stored a code P018F, it means that the powertrain control module (PCM) has detected an issue with the fuel pressure relief valve.
In this case, it indicates that the PCM has detected excessive activation of the fuel pressure relief valve. This valve is designed to release fuel pressure if it becomes too high.
Usually, the fuel pressure relief valve is activated using a solenoid controlled by the PCM. The valve is typically located on the fuel injection rail or the fuel supply line. The PCM monitors the input signal from the fuel pressure sensor to determine if the fuel pressure relief valve needs to operate. When the fuel pressure is relieved, excess fuel is redirected back to the fuel storage tank through a specially designed return hose. When the fuel pressure exceeds a programmed limit, the PCM applies voltage and/or ground to the valve for a sufficient amount of time to initiate operation and reduce the fuel pressure to an acceptable level.
If the PCM detects an unusually high number of requested fuel pressure relief valve activations over a specific period of time, it will store a code P018F and the malfunction indicator lamp (MIL) may illuminate. In some cases, the MIL illumination may require multiple ignition cycles with a failure.
What is the severity of this DTC?
Since excessive fuel pressure can cause serious mechanical damage, a code P018F must be considered severe.
What are some of the symptoms of the code?
The symptoms of a P018F trouble code may include:
What are some of the common causes of the code?
The causes of this P018F transmission code may include:
What are some P018F troubleshooting steps?
Prior to diagnosing a code P018F, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), a manual fuel pressure gauge (with appropriate fittings and attachments), and a reliable source of vehicle information.
After visually inspecting the system wiring and connectors, check all vacuum supply lines and hoses for signs of cracking or collapse. Repair or replace any damaged wiring and vacuum hoses as necessary.
Locate the vehicle’s diagnostic port and connect the scanner to retrieve all stored codes and freeze frame data. It may be helpful to write down this information for future reference, especially if the code is intermittent. Clear the codes and test drive the vehicle to see if the code is immediately reset.
If the code is immediately reset:
Step 1
Check the fuel pressure to determine if it is excessive. If there is no evidence of excessive fuel pressure, suspect a defective fuel pressure sensor or faulty PCM and proceed to Step 3. If the fuel pressure is excessive, move on to Step 2.
Step 2
Use the DVOM and the vehicle information source to test the electronic fuel pressure regulator (if applicable). If the electronic fuel pressure regulator does not meet the manufacturer’s specifications, replace it and test drive the vehicle to ensure that the malfunction is resolved.
If the vehicle is equipped with a mechanical (vacuum operated) fuel pressure regulator, ensure that it has a constant supply of vacuum while the engine is running and that it is not leaking fuel internally. If the fuel pressure is excessive and the regulator has sufficient vacuum, suspect a defective vacuum regulator. If the regulator is leaking fuel internally, consider it defective and replace it. Test drive the vehicle until the PCM enters readiness mode or the code P018F is reset.
Step 3
Use the DVOM and specifications obtained from the vehicle information source to test the fuel pressure regulator according to the manufacturer’s recommendations. Replace the regulator if it fails to meet the specifications. If the sensor and regulator are within specifications, proceed to Step 4.
Step 4
Disconnect all related controllers from the corresponding circuits and use the DVOM to check the resistance and continuity of individual circuits. Repair or replace any circuits that do not meet the manufacturer’s recommendations. If all components and circuits are functioning properly, suspect a defective PCM or a programming error.
