Understanding the Adaptive Cruise Control System

2012 Dodge Durango adaptive cruise control radar.
2012 Dodge Durango adaptive cruise control radar.

A key part of being able to diagnose a problem with Advanced Driver Assistance Systems (ADAS) is understanding how the system works. Knowing what is happening inside the system will help you properly diagnose why the system may be failing. This will prevent replacing parts that are not causing the system issue. Let’s take a look at the inner workings of an adaptive cruise control system (ACC).

Adaptive cruise control systems primarily use cameras and sensors to regulate distance to the vehicle ahead. There are many variations in what is used to detect the distance. Some vehicles use an exposed radar in the front bumper, whereas some use a radar that is hidden behind the front bumper. There are even OEMs, such as Volkswagen or Cadillac, that utilize more than one radar behind the front bumper. Some systems utilize a forward-facing camera, near the review mirror, to help detect vehicle distance. There is at least one OEM that utilizes dual cameras near the rearview mirror to control the adaptive cruise control system.

Radar sensors works by sending radio waves that are reflected off of objects. The time it takes for the radio wave to return indicate how far away the object is, how big the object is, and what direction the object is traveling.

Normally, the radar sensor has its own built-in module. This module makes all the calculations to send and receive signals. Forward facing cameras may also have a module built in. These sensors and cameras detect if there is another vehicle present and the distance to that vehicle. The data from these modules is then sent to other modules in the vehicle, such as the powertrain control module to slow the vehicle if the vehicle ahead is decelerating. There will generally be many modules that use data from the sensor and/or camera. In order for the system to control the vehicle’s speed, information from sensors, such as wheel speed, steering angle, and engine torque, can all contribute to the ACC system. If one of these parts is not functioning properly, it can cause the whole system to fail.

Understanding how the system functions can shorten diagnostic times. Knowing what part of the system to test will help prevent installing parts that don’t actually fix the problem.