P0259 – High level of fuel dosing control of injection pump B

Content

P0259 – OBD-II Trouble Code Technical Description
What does trouble code P0259 mean?
Possible reasons
What are the symptoms of trouble code P0259?
How to diagnose trouble code P0259?
- Diagnostic errors
How serious is trouble code P0259?
What repairs will resolve the P0259 code?

P0259 – OBD-II Trouble Code Technical Description

High level of fuel dosing control of injection pump B

What does the fault code mean P0259?

Code P0259 indicates a high level of injection pump fuel metering control (cam/rotor/injector). This situation occurs when the voltage at the sensor remains above a specified level (usually greater than 4,8 V) for an extended period of time. This is usually due to problems in the electrical circuit. It is important to carry out diagnostics and repairs to avoid affecting fuel delivery and engine performance.

This P0259 diagnostic code applies to various diesel engines equipped with the OBD-II system. It can occur in Ford, Chevy, GMC, Ram, and some Mercedes Benz and VW models. However, troubleshooting procedures may vary depending on the make, model, and vehicle configuration.

The injection pump "B" fuel metering control system typically includes a fuel rack position (FRP) sensor and a fuel quantity drive. The FRP sensor converts the amount of diesel fuel supplied to the injectors into an electrical signal to the powertrain control module (PCM). The PCM uses this signal to determine the amount of fuel supplied to the engine based on current conditions.

Code P0259 indicates that the FRP sensor input signal does not match the normal engine operating conditions stored in the PCM memory. This code also checks the voltage signal from the FRP sensor when the key is initially turned on.

To troubleshoot problems, refer to the repair manual for your specific vehicle brand. Procedures may vary depending on manufacturer, FRP sensor type, and wire color, and will require detailed diagnosis and possibly repair of the electrical circuit.

Possible reasons

Causes of a P0259 code may include:

Short circuit in the FRP sensor signal circuit.
Lost power supply or grounding of the FRP sensor.
FRP sensor failure.
Possible PCM failure (unlikely).
Leaking or damaged fuel injector.
Fuel pump problems.
Engine vacuum leak.
Oxygen sensor malfunction.
Problems with the mass air flow or manifold air pressure sensor.
Poor electrical connections.
PCM failure.

Finding and correcting these problems requires diagnosing and possibly repairing the vehicle's electrical and mechanical components.

What are the symptoms of a fault code? P0259?

Symptoms of a P0259 trouble code may include the following:

Common symptoms:

Low engine power and limited performance.
Abnormal throttle response and difficult cold starting.
Reduced fuel efficiency.
Slow engine operation and increased noise.
ECM/PCM malfunction.
Running the engine with a rich or lean mixture.
Engine misfires and loss of throttle response.
Emissions of smoke from the engine during startup with increased emissions.

Additional symptoms:

Malfunction indicator light (MIL) illumination.
Additional reduction in fuel efficiency.

How to diagnose a fault code P0259?

To effectively diagnose the P0259 code and resolve its causes, follow these steps:

Check technical bulletins (TSB): Start by checking for technical service bulletins associated with your vehicle. Your problem may have already been a known and resolved problem, and the manufacturer has provided an appropriate solution, which can save you time and money when diagnosing.
Find the FRP sensor: Locate the fuel rail position (FRP) sensor on your vehicle. This sensor is usually located inside or on the side of the fuel injection pump and is bolted to the engine.
Inspect the connector and wiring: Carefully inspect the connector and wiring associated with the FRP sensor. Look for scratches, scuffs, damaged wires, burns or melted plastic.
Clean and service the connector: If cleaning the terminals is necessary, use a special electrical contact cleaner and a plastic brush. After this, apply electrical grease to the contact points.
Check with the diagnostic tool: If you have a scan tool, clear the DTCs from memory and see if the P0259 code returns. If this does not happen, the problem may be with the connections.
Check the FRP sensor and its circuit: With the key turned off, disconnect the FRP sensor electrical connector and check the voltage. Connect the black lead of the digital voltmeter to the ground terminal of the connector and the red lead to the power terminal. Turn on the key and check that the readings match the vehicle manufacturers (usually 12V or 5V). If not, repair or replace the power or ground wires, or even the PCM.
Check the signal cable: Move the red voltmeter lead from the power terminal to the signal cable terminal. The voltmeter should read 5V. Otherwise, repair the signal cable or replace the PCM.
Check the fuel system: Inspect the fuel tank, fuel lines, and fuel filter for damage or malfunction.
Check fuel pressure: Take manual fuel pressure readings at the fuel rail and compare them to production specifications. Use a diagnostic scanner to compare these readings with manual readings.
Check the fuel pump and injectors: Carefully check the condition of the fuel injector for damage or leaks, and replace or repair them if necessary. To check the injector operation, use the Noid indicator and perform a sound test.
Check PCM: Check for PCM (engine control module) faults. Although they are not

Diagnostic errors

To effectively diagnose and resolve the problem, the following approach should be followed:

Thorough diagnosis: It is important to conduct a comprehensive analysis of the problem, eliminating the possibility of hidden causes.
Priority components to check: Particular attention should be paid to the following components:

Fuel filter: Check the condition of the filter, as clogging can affect fuel delivery.
Fuel pressure control: Evaluate the performance of the pressure regulator, as its malfunction may cause an error.
Fuel pump: Check the condition of the pump, as faulty pumps may be causing the problem.
Fuel lines: Check the fuel lines for leaks, which could cause the P0259 code.
Powertrain Control Module (PCM): Check the PCM for malfunctions, although such cases are rare, they can affect the fuel delivery system and cause an error.
Wiring and harnesses: Carefully inspect the condition of the electrical wiring and harnesses, as problems in them can be a source of error.

Consistent implementation of all diagnostic stages and a careful examination of each of the listed components will allow you to accurately determine the true cause of the error and begin to eliminate it.