What the P0259 code means
The powertrain control module (PCM) has recognized a discrepancy in the signal voltage that is supplied to the electronic fuel control actuator and the signal returned from the fuel metering control sensor. Please note that this code applies only to diesel-powered vehicles. If this code appears in a vehicle powered by any other propulsion system, that is to say a non-diesel-powered vehicle, you should suspect that you have a defective PCM.
What causes the P0259 code?
There are a few causes for the P0259 code. The most common are a defective fuel pump, a clogged or dirty fuel filter, open or shorted circuits or electrical connectors between the PCM and the fuel control actuator, or a faulty fuel control actuator driver in your vehicle’s PCM.
What are the symptoms of the P0259 code?
You may notice only a stored code or an illuminated Check Engine Light. In more severe cases, you may notice that your vehicle is not starting or that when your vehicle starts it has trouble. You may also notice excessive smoke from your exhaust pipe and engine hesitation or misfiring, especially when you accelerate.
How does a mechanic diagnose the P0259 code?
Diesel engines, like gasoline engines, are controlled using a PCM. In most instances, your vehicle’s PCM provides the fuel control actuator with a voltage signal just before fuel is injected into your cylinders. A sensor in the fuel rail, fuel injection pump, or fuel pressure regulator inputs a voltage signal back to the PCM, and the PCM then uses this input signal to monitor pulse width, volume, and fuel pressure. This is why a scanner, digital volt/ohmmeter, and a fuel pressure gauge will help you to diagnose the potential causes for this code. Always begin your diagnosis with a careful visual inspection of your system’s components, electrical connectors, and circuitry. Repair or replace any items that appear to damaged, disconnected, or contaminated. Next—and this is very important—connect your scanner to your vehicle and record all freeze frame data and stored codes.
Common mistakes when diagnosing the P0259 code
Many replace their vehicle’s injector pump or injectors, which will not solve the problem. In most cases, your fuel filter will need to be replaced, not your injector pump or injectors.
How serious is a P0259
In many cases, a P0259 is very serious, particularly when your vehicle will not start or emits black smoke during acceleration. In most instances, a professional technician should handle a P2059 code. If you do not have the specialized equipment to diagnose the problem, your best bet is to consult a trained technician and have him or her solve the issue for you, or at least offer advice about how you can go about fixing the problem yourself.
What repairs can fix the P0259 code?
Please note that if your vehicle is not starting, then the above information does not apply. If the P0259 code keeps reappearing, you should begin by testing your vehicle’s fuel pressure and delivery volume, and then compare your findings with your manufacturer’s specifications. If fuel pressure is not sufficient, you will need to remove the fuel filter and inspect the filter for debris and dirt. You may need to replace the filter or simply clean it very well. If the filter is clean, you will need to test the fuel pump to be sure that it is working with the ignition switch in the run position. If this is not the case, you should check the fuel pump voltage and ground circuits, and then possibly replace the pump if your battery voltage and ground are present.
Additional comments for consideration regarding the P0259 code
In some cases, a P0259 will prevent your car from starting. Obviously this is something that you will want to fix right away. But please note that fixing this issue can become complicated, and that doing the repairs on your own may involve hours of labor using costly diagnostic equipment. Therefore, it is important to do the correct amount of research before you begin to work.
Need help with a P0259 code?
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