P0257 Injection Pump Fuel Metering Control “B” Malfunction (Cam/Rotor/Injector)

How to diagnose and fix P0257 Injection Pump Fuel Metering Control “B” Malfunction (Cam/Rotor/Injector)

Have you seen a check engine light or other warning message related to your diesel engine’s fuel system? One possible trouble code that may appear is P0257, which refers to a malfunction in the injection pump fuel metering control “B” circuit.

This code can indicate various problems with the camshaft, rotor, or injector, and may affect engine performance, emissions, and fuel economy. In this article, we will explain what P0257 means, how to diagnose it, and what steps you can take to resolve it.

Understanding P0257 and its causes

P0257 is an OBD-II generic code that indicates a fault in the fuel system’s pressure regulator, which controls the amount of fuel that is delivered to the engine. This “B” circuit refers to the second fuel metering control circuit, which may be used in some engine designs. The code may be triggered by a variety of issues, such as:

  • Faulty fuel injector(s), which may be clogged, leaking, or damaged
  • Malfunctioning fuel pump, which may not deliver enough or too much pressure to the injectors
  • Defective camshaft position sensor, which may provide inaccurate signals to the engine control module (ECM)
  • Worn or damaged rotor in the injection pump, which may prevent proper fuel delivery timing
  • Loose or corroded wiring or connectors, which may interfere with the circuit’s signals
  • Failed ECM, which may not be able to control the fuel system properly

Diagnosing P0257 with a scan tool and other tests

To diagnose P0257, you will need a scan tool that can read and clear trouble codes and display live data from the engine and fuel system. You should also perform some visual inspections and basic tests to verify some of the possible causes. Here are the steps you can follow:

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  1. Connect the scan tool to the OBD-II port and check for any related codes or freeze frame data. Note down the code and its description, and clear it from the memory.

  2. Start the engine and observe its behavior, such as idle speed, acceleration, and noise. Listen for any unusual sounds, such as misfires, knocking, or hissing.

  3. Access the live data stream from the fuel system and check the fuel pressure, injection timing, and injector pulse width. Compare these values to the manufacturer’s specifications and look for any deviations or fluctuations.

  4. Inspect the fuel injectors for any signs of leaks, damage, or blockage. You may need to remove them from the engine and test them with a specialized tool or replace them if necessary.

  5. Check the fuel pump and its components, such as the fuel filter, strainer, and regulator, for any issues. Use a fuel pressure gauge to measure the pump’s pressure and flow rate and compare them to the specs.

  6. Test the camshaft position sensor’s signal and resistance using a multimeter or a scope. Look for any variations or interruptions in the signal and check the wiring and connectors for any defects.

  7. Check the injection pump rotor’s condition and clearance using a dial indicator or a feeler gauge. Look for any wear, damage, or misalignment that may affect the fuel flow.

Fixing P0257 with the right repairs and replacements

Once you have identified the root cause of P0257, you can proceed to repair or replace the faulty components. Depending on the severity of the issue and the availability of the parts, you may need to perform some of the following steps:

  • Clean or replace the fuel injectors, flush the fuel system, and change the fuel filter and regulator if necessary.
  • Replace the fuel pump or its components, such as the strainer or check valve, and check the fuel lines and connections for any leaks or blockages.
  • Replace the camshaft position sensor or repair its wiring or connector, and check the reluctor or tone ring for any damage or debris.
  • Replace the injection pump rotor or overhaul the entire pump if necessary, and check the timing belt or chain for any wear or slack.
  • Replace the ECM or reprogram it if necessary, and perform a final test drive to verify that the code has been cleared and the engine runs smoothly.


P0257 Injection Pump Fuel Metering Control “B” Malfunction (Cam/Rotor/Injector) is a common trouble code that may indicate various issues with your diesel engine’s fuel system. By understanding its causes and how to diagnose it, you can save time and money on unnecessary repairs and prevent further damage or safety risks. Remember to use a reliable scan tool and follow the manufacturer’s guidelines and safety precautions. If you need further assistance or have any questions, consult with a qualified technician or mechanic.


Q1. Can P0257 cause my engine to stall or hesitate?
A. Yes, if the fuel pressure or injection timing is affected by the malfunction, the engine may run lean or rich, or experience misfires, backfires, or lack of power.

Q2. Can I drive my vehicle with P0257?
A. It depends on the severity of the issue and the symptoms of the engine. If you notice any abnormal behavior or warning lights, you should stop driving and have your vehicle inspected immediately.

Q3. How much does it cost to fix P0257?
A. The cost varies depending on the cause of the problem and the labor and parts prices. It can range from a few hundred to a few thousand dollars, depending on the type and location of the repair.

Q4. Can I clear P0257 code by disconnecting the battery?
A. Disconnecting the battery may clear the code, but it will also erase other important data and settings from the ECM and may trigger other warning messages. It is not recommended as a permanent solution.

Q5. How often should I check my fuel system for problems?
A. It is recommended to have your fuel system inspected and serviced regularly, depending on the manufacturer’s schedule and your driving habits and conditions. A typical interval may be every 30,000 to 50,000 miles or every two to three years.