What Is the U0109 Code?
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The definition of code U0109 is “Lost Communication With Fuel Pump Control Module A,” although, in some vehicles, it drops the “Module A” description entirely. This code means that your vehicle’s powertrain control module (PCM) or engine control module (ECM) is not able to communicate with your fuel pump control module (FPCM) in some way, typically due to an issue with the Controller Area Network bus communications (CAN). As a generic code, you will find the U0109 code in all engines with a fuel pump control module. It’s most common in gasoline engines, although some diesel engines also use this format.
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Your fuel pump control module monitors and manages most of your fuel delivery process in a returnless fuel system. The fuel pump creates high-pressure levels, allowing fuel to move from the gas tank to the fuel injectors. Of course, the FPCM relies on a signal from other modules to tell it when to move the fuel and how much fuel to move. To communicate with other modules, your vehicle uses a CAN bus. If the CAN bus realizes that the FPCM isn’t communicating effectively, usually by checking a control voltage, it will log this code.
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What Are the Symptoms of a U0109 Code?
The most common symptom of the U0109 code is that your vehicle will crank but won’t actually start. This is because the fuel pump isn’t pumping fuel into the engine. If the vehicle can start, you’ll usually see lowered engine performance and rough running issues, including hesitation, lack of power, poor performance, and misfiring cylinders. You should also see the check engine light turn on.
What Are Some Causes of a U0109 Code?
There are only a few common causes of the U0109 code. A faulty fuel pump control module is a common issue, including both defective fuel pump control module issues and a module that may need reprogramming. Circuitry problems, which may include damaged wiring and poor connections, as well as problems within the wiring harness and connector pins, can also result in this code. Data network problems can also cause this problem, especially if you see additional codes relating to other modules having difficulty communicating. Finally, in some rare cases, it may be due to an issue with the PCM, although this is uncommon.
How Serious Is the U0109 Code?
The U0109 code is extremely serious. Fuel is one of the most important parts of your vehicle, and if your vehicle can’t move fuel into the engine, it won’t be able to run. Even when the problem may not be so severe that it completely shuts your vehicle off, it will still cause rough running issues, and those engine misfires can result in engine damage over time. You should assume that the U0109 code is a top priority and fix it as soon as possible.
Can I Still Drive with a U0109 Code?
Physically, you usually can’t drive with the U0109 code active. It usually results in a no-start condition because it creates problems with fuel delivery, which is important to start the car. You won’t want to drive your vehicle if this code is active, as these problems can cause engine damage, and they can also progress into more serious drivability problems without warning, leading to a dangerous situation on the road. When you know you have this code active, stop driving and get help to fix it.
How Easy Is It to Diagnose a U0109 Code?
Sometimes, diagnosing a generic communication code like this is quite difficult. Even though the problem technically lies within only one or two different systems, diagnosing the core issue within those systems can be quite difficult. To determine whether the problem is a faulty control module or wiring, you need to be able to take in lots of information and determine how the problem is different from a healthy engine. Most people prefer to have an expert manage the diagnostic process for the U0109 code.
How Difficult Is It to Inspect a U0109 Code?
Inspecting the U0109 code is often difficult because it can be hard to see where the problem is. Often, the issues associated with the U0109 code are wiring problems, which means you’ll need some specialty tools, like a digital volt/ohmmeter (DVOM). Plus, you’ll need a source of reliable vehicle information, which may include technical service bulletins, wiring diagrams, and vehicle repair guides. If you lack that knowledge or access to information, talk to a certified mechanic instead.
Need Additional Help with Your U0109 Code?
Most people who experience a problem with the U0109 memory code will need extra help. The good news is that a professional can fix the problem with no follow-up repairs necessary.
Start by finding an auto repair shop in your area. You’ll need a tow truck to bring your vehicle in most of the time, and a local auto repair shop will make it less expensive.
Sometimes, the best way to determine the underlying cause is to look at additional codes in your code scanner. The KBB.com OBD-II database is a great way to understand more about the other diagnostic trouble codes you might see.
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