Freightliner CPC Problems: All You Need to Know to Fix and Avoid Them (2024)

Freightliners are semi-trucks manufactured by the American company of the same name. Freightliners are well known for crafting solid and durable machines. Their semi-trucks have a Common Powertrain Controller (CPC) that serves as the brain hub of the machine. Without a CPC, the Freightliner truck cannot function. Furthermore, if the CPC is experiencing any malfunction or problems, you will likely have problems operating your truck.

In this article, we will outline some common problems of Freightliner CPCs and what you need to know about them. Additionally, we will offer some suggestions for fixing Freightliner CPC problems. Finally, we detail some recommendations for avoiding CPC problems in your Freightliner semi-truck. Before any of that, we will explain what the CPC is. Please keep in mind that we focus on the fourth generation of the Freightliner CPC: CPC4.

Freightliner CPC Problems: All You Need to Know to Fix and Avoid Them (1)

What is a CPC?

The Common powertrain controller (CPC) is a powertrain control module that serves as the brain of the Freightliner truck or any other equipment that uses it. It controls the truck's powertrain and other essential engine functions. The CPC is an interface between the Freightliners Motor Control Module (MCM) and other parts, including the odometer, transmission, gas and brake pedals, brake switches, and dashboard gauges. So, unlike in other automotive systems, The CPC performs the combined functions of an engine control module (ECM) and transmission control module (TCM).

Efficient gear shifting, engine performance, timing, and fuel management are some of the interlinked sub-systems that the CPC manages or controls. So, the CPC constantly monitors inputs on your Freightliner and makes quick adjustments if various readings are out of place. In situations when the CPC cannot rectify an issue itself, it will trigger an error warning for the user to see through gauges and warning lights. This error will also be logged and can be further studied with the use of an onboard diagnostic tool.

Common Freightliner CPC Problems

The CPC is fundamental to the functioning of your Freightliner semi-truck. Without one in good condition, you cannot operate your truck. Below are some common issues that affect Freightliner CPCs.

1) Freightliner Semi-Truck Not Starting

Many issues can cause your semi-truck not to start. One of them is a faulty CPC. One common symptom is the engine cranking without starting. This occurs because the CPC cannot control the many components it regulates to run the powertrain. When driving your semi-truck, you should pay attention to abnormal behaviors (weird sounds, smells, or smoke) that may indicate a problem. This way, you can fix the problem before it becomes a more significant issue.

2) Drivability Issues

Fourth-generation Freightliner CPCs are known to cause issues that affect the driving experience of trucks and even an inability to run. This issue results from a faulty Ball Grid Array (BGA) microprocessor on the CPC's Printing Circuit Board (PCB). The Freightliner CPC gets protection from a conformal coating on the PCB. However, with time high temperatures and vibrations can cause the conformal coating to contract and expand. This situation can cause the solder to break. The effect of a contracted conformal coating is an interruption between the microprocessor and the PCB and will render the semi-truck inoperable.

This problem is fixable and may not necessitate a replacement CPC. However, if you are reading this, it is unlikely that you know how to go about repairing this problem. The repairing process will involve the following:

  • Removing the CPC from the truck.
  • Removing the microprocessor and conformal coating from the CPC.
  • Preparing the boards for resoldering, among many other complex and highly controlled steps.

We advise contacting a qualified service center or repairer for help regarding this issue.

3) Gas Accelerator Pedal Problem

The gas accelerator pedal problem occurs when the truck fails to respond when you press the accelerator pedal. This is also known as dead throttle or lack of accelerator response. This issue can be a severe hazard. While connection problems or damaged cables can cause an accelerator pedal issue, a problem with the CPC can also cause it.

If you are using a scan tool, some common fault codes associated with the gas pedal problem in Freightliner semi-trucks you can look out for include:

  • FMI 4 - accelerator pedal supply voltage failed low
  • FMI 8 - accelerator pedal 2 missing
  • FMI 8 - accelerator pedal signal 1 missing
  • FMI 12 - CPC hardware

These are the fault codes related to the CPC module. You might not see any error codes with some diagnostic devices, but that does not rule out a possible problem with the CPC. The CPC may be faulty if you hit the acceleration without any response.

Without error codes, diagnosing this problem will be difficult without advanced knowledge. You will need expert help to diagnose and fix the problem. If you are sure the CPC is the problem, consult your manual on how to take it out and take it or mail it to qualified technicians for repairs.

4) Increased Emissions

The CPC works to manage many aspects of the Freightliner's functioning. When it works well, it helps optimize engine performance and emissions. If there is a problem with the CPC, performance can suffer and cause increased carbon emissions from your semi-truck. Worse, you might not know that your truck is producing emissions at a higher rate than is accepted without an emissions test.

The issue could be a software problem or a sensor problem. Without carrying out a diagnosis, it will be hard to figure out. You can use a scan tool to check for errors related to this issue or contact an expert for help fixing this.

5) CPC Theft

Outside of performance issues, a significant problem with CPC in America today is CPC theft. Many reports across the USA show that the theft of CPCs has skyrocketed. The belief is that global chip shortages in the last few years have caused this increase in CPC theft. Because of the shortage, replacement modules are not always readily available, creating a scarcity of CPCs and increasing black market prices where they go for much higher than they usually cost.

While a new CPC module will cost around 1400 and 1600 dollars, they cost between 4000 and 8000 dollars on the black market. This high price makes CPCs very attractive to thieves. Once a CPC is stolen and reprogrammed, they are sold and installed on a new truck.

The only fix for a stolen CPC is purchasing a replacement part for your truck. Without replacing the CPC, the truck will not function. There are some things you can do to prevent Freightliner CPC theft; they include:

  • Use password protection for your CPC.
  • Be mindful of your surroundings, especially at night, and research areas you frequent to know where to avoid or be more careful.
  • Park in brightly lit lots with solid surveillance and guards whenever you can.
  • Ensure you close the cab windows and doors while away from the truck.
  • Do not leave your keys in the cab.
  • Equip your Freightliner semi-truck with an alarm and antitheft system.

Fixing The CPC

Any of the issues we mentioned can cause your Freightliner to be inoperable or perform poorly. A failed CPC will lead to the truck deactivating the throttle, making it impossible for you to operate. Fixing the CPC yourself can be difficult because of the complex and delicate technology that it is. If you have a scan device or diagnostic tool, you might be able to diagnose the CPC issues yourself.

However, we recommend getting your Freightliner truck or CPC to a certified technician for proper diagnosis, repair, or replacement.

How To Avoid Freightliner CPC Problems

Regular maintenance is the best way to avoid or prevent problems with semi-trucks or any vehicle. Maintenance and servicing, especially done by experts, will check all necessary aspects of the trucks, including the CPC and the sensors that report to it, to see if they are operable and help to fix error codes. Also, regular maintenance will include software updates for the CPC when available.

Furthermore, any issues you notice when driving the truck should be repaired as soon as possible to prevent further complications. Some warning lights, including the "check engine light," could signal, among other things, an issue with the CPC.


The CPC is the wits of the Freightliner semi-truck, and you must keep it in good working condition for the vehicle to function effectively. The CPC controls and optimizes engine performance, gear shifting, fuel management, emissions, and more. Further, it serves as an interface between various functions of the semi-truck, including the odometer, brake pedals, and dashboard gauges. Yet, as we have seen in this article, the CPC can run into problems.

To avoid these problems, you should frequently carry out maintenance and servicing for your Freightliner. Also, when the semi-truck or CPC shows any signs of a problem, it is crucial to seek the help of qualified repairers who can correctly diagnose and fix this issue. Besides technical issues, you must take special care of the security of your truck because CPC thefts are on the rise, and getting a replacement is expensive.

Freightliner CPC Problems: All You Need to Know to Fix and Avoid Them (2024)
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