An onboard diagnostic, or OBD2 scanner, is a must-have item in every vehicle. And the code you see on the screen in your car is mainly a trouble code. U0109 is also a trouble code. And you can quickly solve this problem and know the reason for it. I will write the details about this in the article.
What is the meaning of the U0109 code?
U0109 code= Lost comm with fuel pump control module
There is a meaning under the code U0109. When the car loses control of the fuel pump module, the OBD2 scanner shows you this code on your car’s screen. This circuit is known as the control area network or CAN bus. This bus primarily scans all of the modules in the vehicle, and if any problems are discovered, a code is displayed on the car screen. So all the modules, wiring, circuit connecting, etc., are related to the CAN bus. If there is a problem with the CAN bus, it’ll be bad news for your car, and you won’t get any information from the OBD 2 scanner then.
The powertrain control module, or PCM, mainly gives information about the fuel pump control module or PCM. If you don’t get any data from the PCM, the fuel module doesn’t work correctly. This problem uplifts diesel for engine usage because this module is mainly used for the gasoline engine. The module’s malfunction can also be influenced by the vehicle’s manufacture, communication type, wire number, and so on.
What are the symptoms of the U0109 trouble code?
If you are careful, you can notice some symptoms in the beginning. This sign will quickly lead you to the problem. Like:
- The car engine starts but is unable to move,
- The malfunction Indicator Light is on,
- The running engine shows some vibration, insufficient power, fault in performance, or misfire in cylinders.
What is the reason for the code U0109?
When you see the code, you may ask why this trouble code is. The U0109 trouble code reason:
- The open or short ground in FPMC.
- Short circuit voltage in fuel pump monitor.
- Poor or faulty connection in the CAN bus.
- Malfunction in the inertia of fuel shutoff.
How to Diagnose the U0109 code?
Diagnosis of the problem of the code U0109 is also straightforward. You need to follow some easy steps to learn about this problem:
- First, if you are in a hurry, I suggest you go with the technical services bulletins or TSBs. These TSBs contain all data about your vehicle, so when technicians run over the data of TSBs, it just saves some time to find the problem. And you also get the solution to fix the problem quickly. So it saves time and saves some money if you can do it yourself.
- The fault can relate to bus communication or faulty battery, so diagnose this side first. Sometimes, you get some fault message from the scanner if this type of trouble code happened before and is erased.
- The malfunction can be related to FPCM. So try to communicate with this module to diagnose the problem. The scanner also shows the trouble code of the relation between GPCM and FPCM. So also check this out.
- Sometimes the module loses power or ground. So you also need to check all the FCPM whether it got powered correctly or not.
How to repair the U0109 OBD code?
There are many steps to repair this problem code, U0109. At first, you can quickly notice the problem with the help of the TSBs list or data. With the data of TSBs, the technician can easily find out the problem and solve it quickly. It is a very efficient method to repair the problem primarily.
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Check FPCM
After that, if you cannot solve the problem, examine the module of FPCM. If you cannot access the code, try to communicate with this module. But when you relate with the FPCM module, it acts like an intermittent or a memory code. They try to connect with GPCM, whether it’s working or not. If you are unable to connect, then the problem is still on. This problem occurs with the loss of power or ground in the module. So check whether the power or ground is working correctly or not in the FPCM module.
If this also can’t help you, try to find the ground connection to the FCM module and check whether this connects tightly or not. If the wire is connected poorly or damaged by accident, you face this problem. And replace or repair this connection.
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Fix CAN-BUS Connection
After that, repair the connection, clean the code from memory and reprogram the system. If the code didn’t pop up again, the problem was solved. But if the code pops up again on the car’s screen, you need to do another step to solve it. Now you need to locate the CAN bus connection and FPCM module connection. First, disconnect the battery cable from the FPCM. Then inspect all the relations between the FPCM module. For locating the problem, check all the wires and connections of the module. Sometimes scraping, bare wires, burn spots, rubbing, or melted spots is the reason for the poor relationship. So pull out the connection and carefully visualize all the terminals inside the links.
If you notice a burning spot or any corrosion, use the electrical contact cleaner or brush to remove this. This brush is used to clean the terminals. Now dry the area and cover it with dielectric silicone grease in the terminal connection.
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Use DVOM
You need to check the voltage before connecting the FCPM with connectors. A digital voltage ohmmeter or DVOM to examine this problem. Now check the power and ground of the FCPM module. The result of the DVOM helps you determine the power and ground, which can come from the FPCM module. When the FPCM disconnects, attach the battery to count the power. If you can read that some battery voltage came out from the FPCM modulator and got good ground in the voltage meter, the result is positive. You got a good power with the perfect ground. If you don’t get the expected answer, I think you know the problem related to the power and ground voltage. Try to repair this problem then.
And if you face the problem, take a look at the CAN bus. You find CAN C+ and CAN C-. Now attach the CAN C+ in the red lead and black lead with the voltmeter. If you got a 2.6 c voltage that fluctuates slightly, then exchange the connection in the red with CAN C-.here. If you got a minimum of 2.4 volts, the CAN bus is working perfectly. But if the FPCM is absent in your vehicle, you need to learn about the communication of PCM and AFCM. Now determine the voltage for their circuit. I think that will help you solve the problem. If you are still unable to repair the code, you need consultation from a professional. That means you need to go to the technician to fix the problem. After solving the problem, they also reprogram the system and remove the old trouble code from memory.
The cost you need to solve the code U0109:
After reading about the solution process, I know you think repairing the problem from the technician will be very costly and time-consuming. But a professional needs around one hour to fix the problem. And the cost is also not so much. You can fix your car U0109 trouble code for only 75$ to 150 $. But this cost varies with the model of your vehicle and the place where you went to repair it. I will give you an idea about the charge and time. So I think it will help you make a budget to fix your car.
This problem is a minor case. You don’t need to change your vehicle after finding the problem. You just face some trouble driving it, like the engine is not starting or suddenly stops working while going. So don’t worry about this. But I suggest you solve the problem as soon as you notice.
Fix Related Trouble Codes: U010c, U0121, U0107
Meet our professional car mechanic, Russell D. Steele, who has been in this field for five consecutive years and works with several automotive companies. He completed the "AUTOMOTIVE & LIGHT DUTY DIESEL TECHNOLOGY" course from NorthWest Lowa Community College, where he learned essential diagnostic and transportation management skills and became a certified mechanic.
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