What Does Check ACC/CMS System Mean? (What Is ACC/CMS System)

If you have not run into these acronyms before, these systems are part of the Wabco RADAR unit that goes from there at the front to the back where the Cummins ECM and Allison transmission reside. They can go bad and cause a lot of problems for you.

The letters ACC means adaptive cruise control and its main duty is to sense the distance between your vehicle and the one in front of you. The adaptive portion puts the brakes on when it senses the distance between your vehicle and the car in front is narrowing.

To learn more about this and the CMS system, just keep reading our article. The information this article contains should help you out when you are seeing alerts and having trouble with your vehicle. Take a few minutes to get familiar with these systems

What is ACC/CMS System?


The ACC is called the Adaptive Cruise Control system and it is similar to regular cruise control except for one thing. It uses radar to judge the distance between your vehicle and the car in front of it.

When engaged and set, the ACC will slow your vehicle down when the car in front slows down. It does this automatically so you do not have to worry. CMS stands for Collision Mitigation system.

Its duty is to keep accidents from happening. This system does not automatically slow your vehicle down. Instead, a camera is mounted near your rearview mirror and monitors what is happening in front of you.

It is actually called CMBS or Collision Mitigation Braking System and what it does is when the camera notices a vehicle or other obstacles in front of you it sounds a buzzer and turns on an alert signal. It is supposed to help you watch the road when you get distracted.

When enacted, it can also tug your seat belt and apply light braking, all to get your attention. Both systems are designed to keep you and your family safe from accidents in their own way.

Both systems are driver-assist features and are not intended to be a replacement for responsible and safe driving. They are there to help you avoid accidents or lower impact speeds to keep everyone in the vehicle safe.

With the ACC system, if it keeps adjusting the speed of the vehicle constantly, you may find it more prudent to turn the system off and drive the vehicle yourself. It is important to keep your vehicle free from dirt, debris, and other contaminants.

Those items will interfere with the system's operation and ruin them. Then if you find that the systems are not working correctly, go to your dealer, etc., and get them repaired right away. These are safety devices that need to be in top shape all the time.

What Does The Check ACC/CMS System Mean?


Like any alert, you receive for other parts on your vehicle, this check ACC/CMS system means you have a problem and need to take care of it. The problem with these systems is that they are not well protected.

A good rain can short them out or cause other damage rendering them useless. This problem is not limited to these two systems. The ECM on an RV sits too low and a heavy rain can affect it as well. One owner sits out heavy rains to make sure there are no problems later on in their holiday.

One thing you have to be cautious about is that there are many electronic parts on an RV that sit too low and are underneath the vehicle. This positioning does create havoc when you are driving through puddles, etc.

The alert may appear when there is a problem with the wiring. For some reason, even over-stretching wires can cause these systems to malfunction. Excess water will not just short out the system. It can obstruct the view of the radar and end up confusing it.

Then the system may shut itself down when it realizes it is not getting the information it thinks it should be getting. There are many reasons why you will have problems with these two systems and the ones mentioned here are just the tip of the iceberg.

Some of those reasons include a miscommunication along the J1939 CANbus system. When a problem does occur, these systems can make a mess with the Allison shifting pattern as well as the Cummins performance

More Detailed Information


In our research, we have come across some posts on an RV discussion forum that are very detailed and lengthy. We will post links to those posts so you can get the information on your own time. They are too lengthy to reproduce here.

We have used some of this information already but felt it is best for you to read it all first hand so you can get the full details about these systems. The poster's name is Gary.Jones and you should read through each thread to make sure you get all the information pertaining to this topic.

The website at the end of this link only has 2 pages of information. The website at the end of this second link has 10 pages to read through. Even though the posts are long and detailed, they contain very important information that we cannot post here.

Some Final Words

The ACC/CMS systems were created and installed for your protection. However, they may not be as protective as they can be. There are too many flaws in the system right now to be effective 100% of the time.

Take the time to read through those posts and do your own research to make sure you know what to do when the systems fail or send you an alert. Being prepared for any event is one of the best ways to keep yourself and your family safe as you travel rough or on any road.

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