P0256 Injection Pump Fuel Metering Control B Malfunction (Cam/Rotor/Injector)

Definition

Common causes

• Faulty fuel injection pump
• Malfunctioning fuel metering valve
• Damaged or worn camshaft or rotor
• Clogged fuel filters
• Low fuel pressure
• Electrical issues (wiring or connectors)
• Faulty fuel injectors
• Contaminated fuel
• ECM (Engine Control Module) issues
• Vacuum leaks in the fuel system

Common misdiagnoses

• Fuel injector failure
• Fuel pump issues
• Fuel filter blockage
• Air intake leaks
• Engine control module (ECM) failure
• Wiring or connector problems
• Low fuel pressure
• Camshaft or crankshaft position sensor failure
• Timing belt or chain issues
• EGR valve malfunction

Troubleshooting steps

1. 1. Check for Additional Codes

   Use an OBD-II scanner to check for any other related trouble codes. This can provide more context and help identify if there are other issues affecting the fuel system

2. 2. Inspect Wiring and Connectors

   Visually inspect the wiring and connectors related to the fuel injection system, including the injection pump, camshaft, and fuel injectors. Look for signs of damage, corrosion, or loose connections

3. 3. Repair or replace any damaged wiring or connectors

4. 4. Check Fuel Supply

   Ensure that the fuel tank has an adequate supply of fuel

5. 5. Inspect the fuel lines for blockages, leaks, or kinks that could restrict fuel flow

6. 6. Check the fuel filter for clogs and replace it if necessary

7. 7. Test the Fuel Pump

   Verify that the fuel pump is functioning correctly. You can do this by checking the fuel pressure with a gauge to ensure it meets the manufacturer’s specifications

8. 8. Listen for the fuel pump operation when the ignition is turned on

9. 9. Inspect the Injection Pump

   Check the injection pump for proper operation. Look for signs of wear or damage

10. 10. If applicable, test the pump’s electrical connections and sensors

11. 11. Examine the Fuel Injectors

    Inspect the fuel injectors for proper operation. This may involve checking for leaks, clogs, or electrical issues

12. 12. Perform a resistance test on the injectors to ensure they are within specifications

13. 13. Check the Camshaft and Rotor

    If the vehicle has a mechanical injection pump, inspect the camshaft and rotor for wear or damage

14. 14. Ensure that the timing of the injection pump is set correctly according to the manufacturer’s specifications

15. 15. Scan for Sensor Issues

    Check the operation of relevant sensors, such as the crankshaft position sensor and camshaft position sensor, as they can affect fuel metering

16. 16. Test the sensors for proper voltage and signal output

17. 17. Perform a Visual Inspection

    Look for any signs of fuel leaks around the injection system, which could indicate a problem

18. 18. Check for any vacuum leaks in the intake system that could affect engine performance

19. 19. Clear Codes and Test Drive

    After performing repairs or adjustments, clear the trouble codes using the OBD-II scanner

20. 20. Take the vehicle for a test drive to see if the code returns.1

21. 21. Consult Technical Service Bulletins (TSBs)

    Check for any manufacturer-specific TSBs related to the P0256 code, as there may be known issues or recalls that could apply to your vehicle.1

22. 22. Seek Professional Help

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with diesel fuel systems or the specific vehicle make and model. By following these troubleshooting steps, you can systematically identify and address the underlying issues causing the P0256 code