What does the P0251 code mean?

This generic powertrain diagnostic code can apply to all OBD-II diesel vehicles (e.g., Ford, Chevy, GMC, Ram, etc.), but it is more common on certain Mercedes-Benz and Volkswagen models.

Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

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Technical Description

The Fuel Injection Pump “A” Metering Control Circuit is typically mounted inside or on the side of the injection pump, which is itself attached to the engine. This circuit generally includes:

• A Fuel Rail Pressure (FRP) sensor
• A Fuel Metering Actuator

The FRP sensor measures the amount of fuel sent to the injectors and sends this information to the PCM (Powertrain Control Module) as an electrical signal.

The PCM uses this signal to adjust the amount of fuel injected based on the engine’s operating conditions. Code P0251 is stored if this signal does not match the expected values, even briefly, or if an anomaly is detected when the ignition is turned on.

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Code Severity

The severity of code P0251 is generally low, as the PCM can often temporarily compensate for an electrical failure. However, the problem can affect performance or fuel consumption.

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Possible Symptoms

• Malfunction Indicator Lamp (MIL) illuminated
• Decreased fuel economy

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Common Causes

Possible causes of this code include:

• Open circuit in the signal wire to the FRP sensor
• Short to voltage in the signal circuit
• Short to ground in the signal circuit
• Interrupted power or ground to the sensor
• Faulty FRP sensor (likely)
• Faulty PCM (rare)

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Diagnostic and Troubleshooting Steps

1. Check Technical Service Bulletins (TSBs): Some manufacturers publish specific fixes for known issues.
2. Locate the FRP sensor: It is usually found on or inside the injection pump.
3. Visual Inspection:
   • Check the wiring: wear, burns, exposed wires, corrosion.
   • Inspect the connector: oxidized or melted terminals.
   • Clean if necessary with contact cleaner and apply electrical grease.
4. Clear the code with a diagnostic tool and check if it returns.
5. Voltage Test:
   • Disconnect the FRP sensor.
   • Measure the supply voltage (key ON, engine OFF). Expected result: 5V or 12V.
   • If absent: repair the wiring or replace the PCM.
6. Signal Test:
   • Measure the voltage on the signal wire (connector still disconnected). Expected result: 5V.
   • Otherwise, repair the signal wire or replace the PCM.

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Replacing the FRP Sensor or PCM

If all tests are correct but the P0251 code persists, it is likely that the FRP sensor or metering actuator is faulty.

As a last resort, the PCM may be at fault, but its replacement requires vehicle-specific programming/calibration.

⚠️ If in doubt, consult a qualified automotive technician for a thorough diagnosis.

Code P0252: Injection Pump Fuel Metering Control “A” Circuit Malfunction
Complete guide to diagnosing and resolving the issue

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1. What is code P0252?

P0252 is a generic OBD-II code related to the Injection Pump Fuel Metering Control “A” Circuit, commonly found on diesel vehicles (Ford, Chevy, Mercedes, VW, etc.). It indicates a range/performance problem in the fuel control system, often linked to the Fuel Rail Pressure (FRP) sensor or its electrical circuit.

Fuel Metering Circuit Operation

• The FRP sensor converts the amount of fuel delivered by the pump into an electrical signal for the PCM.
• The PCM uses this signal to regulate fuel injection based on engine demands.
• If the FRP signal falls outside expected parameters, the PCM stores code P0252.

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2. Severity of Code P0252

• Mechanical failure (e.g., faulty injection pump): Severe (risk of stalling or engine damage).
• Electrical issue (e.g., short circuit): Moderate (PCM may partially compensate).

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3. Common Symptoms

• Malfunction Indicator Lamp (MIL) illuminated.
• Decreased fuel economy.
• Occasionally: Rough idle or power loss.

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4. Possible Causes

Electrical Problems

• Open or short circuit (to ground or voltage) in the FRP signal wire.
• Faulty power supply or ground to the FRP sensor.
• Corrosion in connectors or damaged wiring.

Mechanical/Electronic Failures

• Faulty FRP sensor (most likely cause).
• Failed fuel quantity actuator.
• Rare: PCM failure (check as last resort).

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5. Troubleshooting Steps

Preliminary Checks

1. Check Technical Service Bulletins (TSBs): A known fix may exist for your model.
2. Visual inspection:

• Locate the FRP sensor (mounted on injection pump).
• Check connectors, wires, and terminals for corrosion, burn marks, or physical damage.
• Clean contacts with electrical spray and apply dielectric grease.

Electrical Tests

1. Power and ground test:

• Disconnect FRP connector.
• Measure voltage between power terminal and ground (ignition ON).
• Expected: 5V or 12V (per manufacturer specifications).
• If out of range: Check power circuit or PCM.

1. Signal wire test:

• Measure voltage at signal terminal (ignition ON).
• Expected: 5V.
• If abnormal: Repair wiring or replace PCM.

FRP Sensor Replacement

• If electrical tests are normal but code persists, replace the FRP sensor or fuel quantity actuator.
• Note: Some PCMs require reprogramming after replacement.

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6. Conclusion

P0252 indicates a malfunction in the fuel metering circuit, often related to the FRP sensor. While basic checks (connectors, voltage) are DIY-friendly, professional diagnosis is recommended for advanced testing or PCM replacement. Ignoring this code may lead to increased fuel consumption or engine damage.

🔧 Tip: Use a vehicle-specific repair manual to accurately identify the “A” circuit and technical specifications.

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 “A” injection pump metering control circuit is typically found mounted inside/on the side of the injection pump bolted to the engine. The “A” injection pump metering control circuit is generally composed of a Fuel Rail Pressure (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 engine 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.

The code P0253 Injection Pump Fuel Metering Control “A” 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 a period. This code is generally considered an electrical circuit issue. Refer to a vehicle-specific repair manual to determine which part is the “A” 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 compensate adequately.
What are some of the symptoms of the code?

Symptoms of a P0253 trouble code may include:

Malfunction Indicator Lamp (MIL) illumination
Decreased fuel economy

What are some of the common causes of the code?

Causes

of this P0253 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 troubleshooting steps for P0253?

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-bristled 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 P0253 code returns. If it does not, the connections were likely your problem.

If the P0253 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 P0253, 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.

The P0254 code indicates a malfunction in the fuel metering control circuit of injection pump “A”, with a signal that is too high detected. This typically concerns diesel engines and often involves an electrical issue in the fuel rail pressure (FRP) sensor circuit or the fuel metering actuator.

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⚙️ Summary of Code P0254

• Full name: P0254 – Injection Pump “A” Fuel Metering Control, High Signal (cam/rotor/injector)

• Severity: Low to moderate — risk of inefficient engine operation, but rarely immobilizing

• Code type: OBD-II, especially on diesel engines

• Role of the affected part: To precisely regulate the amount of fuel injected according to engine demand

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🔧 Possible Causes

• ✅ Short circuit to voltage in the FRP sensor signal wire

• ✅ Open wires or loose/corroded/melted connector

• ✅ Defective FRP (Fuel Rail Pressure) sensor

• ⛔ Defective PCM (engine control module) (rare)

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⚠️ Typical Symptoms

• Illumination of the check engine light (MIL)

• Reduced engine performance

• Loss of fuel economy

• Rough idle or stalling

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🛠️ Diagnostic/Repair Steps

1. Visual Inspection

• Locate the FRP sensor (often attached to the injection pump),

• Carefully inspect:

  • Cut, melted, or corroded wires,

  • Loose or oxidized connectors (green tint),

  • Clean and apply dielectric grease if necessary.

2. Voltage Tests

Using a digital voltmeter (DVOM):

a. Power Supply Test

• Ignition on, engine off,

• Measure the voltage between the FRP sensor’s power terminal and ground.

• Expect approximately 5 to 12 volts depending on the system. If not within range, faulty wiring or PCM.

b. Signal Test

• Measure between the signal wire and ground,

• You should have about 5 volts if the sensor is idle. A persistent high voltage (>4.8V) triggers P0254.

3. Sensor Replacement

• If the voltage is still incorrect and the wiring is good, replace the FRP sensor.

4. Code Clearing and Road Test

• Clear the code with an OBD-II scanner,

• Test the vehicle under normal conditions,

• If the code returns: consider replacing the PCM (as a last resort, with reprogramming).

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📌 Important Note

Some brands like Mercedes, VW, Ford, or GM have specific variations for this code. It may be helpful to consult TSBs (technical service bulletins) or have a manufacturer’s manual to know the specifics (exact location, wire colors, voltage ranges, etc.).

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 fuel metering control circuit is typically found mounted inside/on the side of the injection pump bolted to the engine. The “B” injection pump fuel metering control circuit is generally composed of a Fuel Rail Pressure (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 engine 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 voltage signal to determine if it is correct at initial key-on.

The P0255 code – Injection Pump “B” Fuel Metering Control Intermittent (Cam/Rotor/Injector) – could have been set due to mechanical issues (typically EVAP system mechanical problems) or electrical issues (FRP sensor circuit). These cannot be overlooked during the troubleshooting phase, especially when dealing with an intermittent issue. Refer to a vehicle-specific repair manual to determine what the “B” circuit part is 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 depends on the failure. In case of mechanical failure; severe. In case of electrical failure, less severe, which the PCM can adequately compensate for.
What Are Some of the Symptoms of the Code?

Symptoms of a P0255 trouble code may include:

Malfunction Indicator Lamp (MIL) illumination
Decreased fuel economy

What Are Some of the Common Causes of the Code?

Causes

of this P0255 code may include:

Open in the signal circuit to the FRP sensor – Possible
Short to voltage in the signal circuit to the FRP sensor – Possible
Short to ground in the FRP sensor signal circuit – Possible
Open in power or ground at the FRP sensor – Possible
Failed FRP sensor – Probable
Failed PCM – Unlikely

What Are the P0255 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 green 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 the memory and see if the P0255 code returns. If it does not, the connections were likely your problem.

If the P0255 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 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 pass and you continue to get a P0255, 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.

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 fuel metering control circuit is typically found mounted inside/on the side of the injection pump bolted to the engine. The “B” injection pump fuel metering control circuit is generally composed of a fuel rail pressure (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 engine 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 voltage signal to determine if it is correct at initial key-on.

The code P0256 Injection Pump “B” Fuel Metering Control Malfunction (Cam/Rotor/Injector) may have been set due to mechanical issues (usually EVAP system mechanical problems) or electrical issues (FRP sensor circuit). These cannot be overlooked during the troubleshooting phase, especially when dealing with an intermittent 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 high. Since it is an electrical fault, the PCM can adequately compensate.
What are some of the symptoms of the code?

Symptoms of a P0256 trouble code may include:

Illumination of the Malfunction Indicator Lamp (MIL)
Decreased fuel economy

What are some common causes of the code?

Causes

of this P0256 code may include:

Open in the signal circuit to the FRP sensor – possible
Short to voltage in the signal circuit to the FRP sensor – possible
Short to ground in the FRP sensor signal circuit – possible
Open in power or ground to the FRP sensor – possible
Failed FRP sensor – probable
Failed PCM – unlikely

What are the P0256 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 during diagnosis.

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-bristled 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 the memory and see if the P0256 code returns. If it does not, the connections were likely your problem.

If the P0256 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 is successful, 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 are successful and you continue to get a P0256, this would most likely indicate a failed 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 help from a qualified automotive diagnostician. PCMs need to be programmed or calibrated to the vehicle to be installed correctly.

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 Fuel Metering Control circuit is typically found mounted inside/on the side of the injection pump bolted to the engine. The “B” Injection Pump Fuel Metering Control circuit is generally composed of a Fuel Rail Pressure (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 engine 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 voltage signal to determine if it is correct at initial key-on.

The P0257 Injection Pump Fuel Metering Control B Range/Performance (Cam/Rotor/Injector) code may have been set due to mechanical issues (often EVAP system mechanical problems) or electrical issues (FRP sensor circuit). These cannot be overlooked during the troubleshooting phase, especially when dealing with an intermittent issue. Refer to a vehicle-specific repair manual to determine what the “B” part of the circuit is 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 depends on the failure. In case of mechanical failure; severe. In case of electrical failure, less severe, which the PCM can adequately compensate for.
What Are Some of the Symptoms of the Code?

Symptoms of a P0257 fault code may include:

Malfunction Indicator Light (MIL) illumination
Decreased fuel economy

What Are Some Common Causes of the Code?

Causes

of this P0257 code may include:

Open in the signal circuit to the FRP sensor – possible
Short to voltage in the signal circuit to the FRP sensor – possible
Short to ground in the FRP sensor signal circuit – possible
Open in power or ground at the FRP sensor – possible
Failed FRP sensor – probable
Failed PCM – unlikely

What Are the P0257 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 green 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 the memory and see if the P0257 code returns. If it does not, the connections were likely your problem.

If the P0257 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 is successful, 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 are successful and you continue to get a P0257, 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 help from a qualified automotive diagnostician. PCMs need to be programmed or calibrated to the vehicle to be installed correctly.

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.

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 generally consists 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 deliver into the engine based on engine 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 P0259 Injection Pump “B” Fuel Metering Control High (Cam/Rotor/Injector) is set when the voltage at the sensor remains above a defined level (usually above 4.8 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 high. Since it is an electrical fault, the PCM can compensate adequately.
What are some of the symptoms of the code?

Symptoms of a P0259 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 P0259 code may include:

Short to power in the FRP sensor signal circuit – possible
Open in power or ground to the FRP sensor – probable
Faulty FRP sensor – possible
Failed PCM – unlikely

What are the P0259 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 published by the manufacturer and can save you time and money during diagnosis.

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 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 P0259 code returns. If it does not, the connections were likely your problem.

If the P0259 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 on the FRP sensor wiring harness connector. Connect the red wire from the digital voltmeter to the power supply terminal on 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 is successful, 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 are successful and you continue to get a P0259, 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.