Technical Description of OBD-II Trouble Code
The circuit for the sensor in the low pressure fuel system is registering a high voltage.
What does that mean?
This diagnostic trouble code for powertrain/engine issues is 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) is typically located directly on the fuel rail, near the injectors and intake manifold. The FPS converts the fuel pressure in the system into an electrical signal for the Powertrain Control Module (PCM).
The PCM receives this voltage signal, along with possibly another signal from the Fuel Temperature Sensor (FTS), which may or may not be integrated with the FPS. The PCM analyzes the FPS sensor voltage to determine the precise amount of fuel to inject into the engine. This code is triggered if these inputs remain above a certain threshold for an extended period of time. The PCM also checks the voltage signal from the FPS sensor during initial Key On to ensure its accuracy. This code is usually set due to electrical issues with the fuel pressure sensor circuit.
The troubleshooting steps may vary depending on the manufacturer, type of FPS/FTS sensor, and wire colors.
Symptoms
The symptoms of a P2542 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 screwed or mounted directly onto the fuel rail, near the injectors and intake manifold. Once located, visually inspect the connector and wiring. Look for any signs of scraping, rubbing, bare wires, burn spots, or melted plastic. Separate the connector and carefully examine the terminals (metal parts) inside. Check for any signs of burning or 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 to the contact points.
If you have a scan tool, clear the diagnostic trouble codes from memory and check if the P2542 code reappears. If it does not, then the issue was most likely related to the connections.
If the P2542 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 of the FP sensor wiring harness connector. Connect the red lead of the Digital Voltmeter to the power terminal of the FP sensor wiring harness connector. Turn the Key On, but keep the Engine Off. Check the manufacturer’s specifications; the voltmeter should read either 12 volts or 5 volts. If not, repair the wiring on the power or ground side, or replace the PCM.
If the previous test is successful, 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 the open in the signal wire, or replace the PCM.
If all previous tests have passed and you continue to receive a P2542 code, it is likely that the FPS sensor has failed. However, 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.
