Meaning of Code P109D
A flexible fuel vehicle (FFV) can operate with fuel containing a high concentration of ethyl alcohol.
This type of vehicle uses a fuel pressure switching system that adjusts the pressure between a low mode and a high mode via a fuel pressure switching valve.
Code P109D is recorded when a malfunction is detected in the fuel pressure switching valve circuit. If the circuit voltage is different from the voltage commanded by the engine control module (ECM), the ECM interprets this as an open or short-circuited circuit and stores a DTC.
Possible Symptoms
- Check engine light on (or “service engine soon” warning light).
Possible Causes
- Faulty fuel pressure switching valve
- Fuel pressure switching valve harness open or short-circuited
- Poor electrical connection of the fuel pressure switching valve circuit
- Faulty F/PMP VSV relay
- Faulty engine control module (ECM)
Diagnostic and Repair Procedures
1. Visual Inspection
- Check the condition of the wiring harness and connectors associated with the fuel pressure switching valve.
- Look for damaged wires, broken, bent, pushed, or corroded connector pins.
- Ensure electrical connections are tight and free of corrosion.
2. Checking the Fuel Pressure Switching Valve
- Using a digital multimeter, measure the resistance of the fuel pressure switching valve.
- Compare the obtained values with the manufacturer’s specifications.
- Replace the valve if it does not meet the recommended values.
3. Checking the Wiring Harness
- Test the continuity of the wires between the ECM and the fuel pressure switching valve.
- Check for the absence of short circuits or open circuits using a multimeter in ohmmeter mode.
- Repair or replace any damaged wiring.
4. Checking the F/PMP VSV Relay
- Identify the relay responsible for powering the fuel pressure switching valve.
- Test its proper operation using a multimeter or by replacing it with a known good relay.
5. Checking the Engine Control Module (ECM)
- If all previous checks are correct, advanced testing of the ECM module may be necessary.
- Consult a specialist or qualified technician to perform an in-depth diagnosis.
Conclusion
Code P109D indicates a potential problem with the fuel pressure switching valve circuit. A thorough inspection of the harness, connections, and proper operation of the electrical components will help identify and resolve the cause of the issue.