What does it mean?
This generic powertrain/engine diagnostic code can generally apply to all engines equipped with an OBD-II diesel engine (e.g., Ford, Chevy, GMC, Ram, etc.), but appears more frequently in some Mercedes Benz and VW vehicles.
Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.
The “B” injection pump metering control circuit is typically found mounted inside/on the side of the injection pump bolted to the engine. The “B” injection pump metering control circuit is generally composed of a fuel rail position (FRP) sensor and a fuel quantity actuator.
The FRP sensor converts the amount of diesel fuel supplied by the fuel quantity plunger to the injectors into an electrical signal for the Powertrain Control Module (PCM).
The PCM receives this voltage signal to determine the amount of fuel it will put into the engine based on the engine’s operating conditions. This code is set if this input does not match the normal engine operating conditions stored in the PCM’s memory, even for a second, as indicated by this diagnostic code. It also checks the FRP sensor’s voltage signal to determine if it is correct at initial key-on.
Code P0258 Injection Pump B Fuel Metering Control Low (Cam/Rotor/Injector) is set when the voltage at the sensor remains below a defined level (usually under 0.3 V) for too long. This code is generally considered an electrical circuit issue. Refer to a vehicle-specific repair manual to determine which part is the “B” circuit for your particular application.
Troubleshooting steps may vary depending on the manufacturer, FRP sensor type, and wire colors.
How severe is this DTC?
The severity in this case will not be serious. Since it is an electrical failure, the PCM can adequately compensate.
What are some of the symptoms of the code?
Symptoms of a P0258 fault code may include:
Malfunction Indicator Lamp (MIL) illumination
Decreased fuel economy
What are some of the common causes of the code?
Causes
of this P0258 code may include:
Short to ground in the FRP sensor signal circuit – possible
Short to ground or open in the FRP sensor power circuit – possible
Failed PCM – unlikely
What are the P0258 troubleshooting steps?
A good starting point is always to check the Technical Service Bulletins (TSBs) for your vehicle. Your issue may be a known problem with a known fix issued by the manufacturer and can save you time and money when diagnosing.
Next, locate the FRP sensor on your vehicle. This sensor is typically found mounted inside/on the side of the injection pump bolted to the engine. 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 burned 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 P0258 code returns. If it does not, the connections were likely your problem.
If the P0258 code returns, we will need to test the FRP sensor and its associated circuits. With the key off, disconnect the electrical connector from the FRP sensor. Connect a black wire from the digital voltmeter to the ground terminal at the FRP sensor wiring harness connector. Connect the red wire from the digital voltmeter to the power supply terminal at the FRP 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 power or ground wire 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 signal wire or replace the PCM.
If all previous tests have passed and you continue to get a P0258, this would most likely indicate a failing FRP sensor/fuel quantity actuator, although a faulty PCM cannot be ruled out until the FRP sensor/fuel quantity actuator 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.