Technical Description of OBD-II Trouble Code
Circuit for Low Pressure Fuel System Sensor
What does that signify?
This generic powertrain/engine diagnostic trouble code can typically be applicable to all engines equipped with OBDII, but it is more commonly found in certain Audi, Ford, and VW vehicles.
The Fuel Pressure Sensor (FPS) converts the fuel pressure in the system into an electrical signal for the Powertrain Control Module (PCM).
The PCM receives this voltage signal and possibly another one; the Fuel Temperature Sensor (FTS), which may or may not be part of the FPS. The PCM analyzes the voltage from the FPS sensor to determine the precise amount of fuel to inject into the engine. This code is triggered if these inputs vary too much. It also examines the voltage signal from the FPS sensor to verify its accuracy during the initial Key On Engine Off. This code could be triggered by mechanical (typically fuel pressure/volume) or electrical (fuel pressure sensor circuit) issues.
Troubleshooting steps may differ depending on the manufacturer, type of FPS/FTS sensor, and wire colors.
Symptoms
The symptoms of a P2539 engine code may include:
Causes
Possible causes for this code to be triggered are:
Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSB) for your particular vehicle. Your issue may be a known problem with a known solution provided by the manufacturer, which can save you time and money during diagnosis.
Next, locate the FPS sensor on your specific vehicle. This sensor is usually found directly screwed into the fuel rail, close to the injectors and the intake manifold. Once located, visually inspect the connector and wiring. Look for scraping, rubbing, bare wires, burn spots, or melted plastic. Disconnect the connector and carefully examine the terminals (the metal parts) inside the connector. Check if they appear burned or have a green tint indicating corrosion. If necessary, clean the terminals using electrical contact cleaner and a plastic bristle brush. Allow them to dry and apply electrical grease where the terminals make contact.
If you have a scan tool, clear the diagnostic trouble codes from memory and check if the P2539 code reappears. If it does not, then the issue was most likely related to the connections.
If the P2539 code does reappear, you will need to test the FPS sensor and its associated circuits. With the Key Off, disconnect the electrical connector at the FP sensor. Connect the black lead of a Digital Voltmeter to the ground terminal at the FP sensor wiring harness connector. Connect the red lead of the Digital Voltmeter to the power terminal at the FP sensor wiring harness connector. Turn the Key On Engine Off. Check the manufacturer’s specifications; the voltmeter should read either 12 volts or 5 volts. If not, repair any open circuits in the power or ground wire, or replace the PCM.
If the previous test passed, you will need to test the signal wire. With the connector still disconnected, move the red lead of the voltmeter from the power wire terminal to the signal wire terminal. The voltmeter should now read 5 volts. If not, repair any open circuits in the signal wire, or replace the PCM.
If all previous tests have passed and you continue to receive a P2539 code, it most likely indicates a failed FPS sensor, although a failed PCM cannot be ruled out until the FPS sensor has been replaced. If you are unsure, seek assistance from a trained automotive diagnostician. PCMs must be programmed or calibrated to the vehicle in order to be installed correctly.
