Symptoms
Symptoms of a P2543 engine code may include:
- Malfunction indicator lamp illuminated
- No start condition
- Longer than normal cranking times
- Hesitation during acceleration
- Decreased fuel economy
Causes
Potential causes for this code definition include:
- Open in signal circuit to FP sensor – possible
- Short to voltage in signal circuit to FP sensor – possible
- Short to ground in signal circuit to FP sensor – possible
- Open in power or ground at FP sensor – possible
- Faulty fuel pressure sensor – probable
- Failed PCM – unlikely
Diagnostic and Repair Procedures
A good starting point is always to check the technical service bulletins (TSBs) for your specific vehicle. Your issue may be a known problem with a known fix published by the manufacturer and can save you time and money when diagnosing.
Next, locate the FPS sensor on your specific vehicle. This sensor is typically directly screwed/mounted into the fuel rail, near the injectors and intake manifold. Once located, visually inspect the connector and wiring. Look for chafing, rubbing, bare wires, burns, or melted plastic. Disconnect the connector and carefully inspect the terminals (the metal parts) inside the connector. See if they look burnt or have a greenish tint indicating corrosion. Use electrical contact cleaner and a plastic bristle brush if cleaning the terminals is necessary. Let it dry and apply electrical grease where the terminals make contact.
If you have a scan tool, clear the diagnostic codes from memory and see if the P2543 code returns. If it does not, the connections were likely your problem.
If the P2543 code returns, ensure you have good fuel pressure by testing with a mechanical gauge. Check your vehicle manufacturer’s specifications. If fuel pressure and volume do not meet specifications, replace the fuel pump, clear the codes, and retest. If the P2543 is now gone, then the problem was mechanical.
If the P2543 code returns, we will need to test the FPS sensor and its associated circuits. With the key off, disconnect the electrical connector from the FP sensor. Connect a black wire from the digital voltmeter to the ground terminal at the FP sensor wiring harness connector. Connect the red wire from the digital voltmeter to the power supply terminal at the FP sensor wiring harness connector. Turn the key to the engine off position. Check the manufacturer’s specifications; the voltmeter should read 12 volts or 5 volts. If not, repair the open in the power or ground wiring or replace the PCM.
If the previous test passes, we will need to test the signal wire. With the connector still disconnected, move the red voltmeter wire 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 pass and you continue to get a P2543, this would most likely indicate a failing FPS sensor, although a faulty PCM cannot be ruled out until the FPS sensor has been replaced. If in doubt, seek assistance from a qualified automotive diagnostician. PCMs must be programmed or calibrated to the vehicle to be installed correctly.