System Description

System Description

The adaptive cruise control (ACC) system automatically controls the vehicle speed, within the set speed, to maintain a safe distance to the vehicle ahead.

Operation Criteria
- When there is no vehicle ahead, adaptive cruise control (ACC) maintains the set speed.
- When there is a vehicle ahead, the adaptive cruise control (ACC) maintains a set distance within the set speed.
- If the vehicle ahead pulls over out of the way, the adaptive cruise control (ACC) accelerates the vehicle to the set speed and maintains that speed.
- The adaptive cruise control (ACC) measures the distance from the vehicle ahead using the millimeter wave radar unit, and it determines if the target vehicle driving ahead is in the same lane by using inputs from the vehicle speed sensor and the yaw rate sensor.
- If the adaptive cruise control (ACC) detects a slow vehicle and the distance to the vehicle ahead is closing, the vehicle speed is reduced primarily by closing the throttle, and additional slowing is accomplished by using the brakes. If the vehicle ahead is too close, an alarm sounds.
- If a slower vehicle ahead accelerates, the throttle is opened to accelerate the vehicle (up to the set speed.) to maintain the following distance.

Basic Adaptive Cruise Control (ACC) Pattern

- Radar detection: Max. 0.06 mile (100 m) ahead in a 16 degrees field of view
- Vehicle operating speed: 25-90 mph (40-145 km/h)

Adaptive Cruise Control (ACC) Unit

The adaptive cruise control (ACC) unit obtains information from external sensors and switches that are connected to their respective control units.

Adaptive Cruise Control Operation Range:
- Setting speed range is 25-90 mph (20-145 km/h)
- Setting following distance from vehicle ahead is 1.0-2.0 seconds
- Maximum deceleration is 0.30 G

Millimeter Wave Radar Unit

The millimeter wave radar unit is installed on the front bulkhead on the main bracket. The main bracket allows the radar unit angle to be adjusted ±3 degrees vertically and horizontally (the horizontal adjustment includes the ±2 degrees of auto-aiming margin) by moving the main bracket adjusters. The millimeter wave radar unit has these functions:

Basic distance function
The millimeter wave radar unit radiates 76-77 GHz radar waves with in a range of 328 ft (100 m) ahead and 16 degrees horizontally and 3.9 degrees vertically, and it receives the reflected waves. In doing so, it can calculate the distance from the vehicle ahead, the relative speed (the difference of speed between two vehicles), and position and output the data to the adaptive cruise control unit.

Aiming function
The millimeter wave radar unit has a horizontal auto-aiming function and runs auto aiming in the range of ±2 degrees in accordance with the directions from the adaptive cruise control (ACC) unit. It also has a mechanical adjustment mechanism that covers the range that the auto-aiming cannot.

Self-diagnosis function
The millimeter wave radar unit has a self-diagnostic function, and it outputs the self-diagnostic information to the adaptive cruise control (ACC) unit.

Sensitivity-lowering detection function
When the detecting performance of the radar is deteriorated by dirt, dust, or other contaminants, it signals the condition malfunction to the adaptive cruise control (ACC) unit until the performance is restored.

Adjuster-misalignment detection function
When more than ±5 degrees of adjuster misalignment is detected while driving, it signals the condition to the adaptive cruise control (ACC) unit.

Brake Fluid Pressure Sensor

The brake fluid pressure sensors are installed in the right and left sides of the brake line 4-way joint. The brake fluid pressure is converted to a signal (voltage value) and is output to the adaptive cruise control (ACC) unit. The adaptive cruise control (ACC) unit is always monitoring the adaptive cruise control (ACC) brake operation and the brake pressure controlled by the signal sent from the brake fluid pressure sensor.

Gauge Control Module

When the adaptive cruise control (ACC) system is working, the adaptive cruise control (ACC) activation indicator (green) comes on and the working condition is displayed on the multi-information display (MID). If a system problem is detected, the adaptive cruise control (ACC) indicator (amber) comes on and it is displayed on the MID.

Adaptive Cruise Control (ACC) System Related Switches

The switches are installed on the right side of the steering wheel for ease of operation.

How to Troubleshoot DTCs

Check and clear the DTCs with the HDS. Before troubleshooting, check and note these items:
- Ask the customer about the conditions when the problem occurred, and try to reproduce the same conditions for troubleshooting.
- If the symptom does not appear and the adaptive cruise control (ACC) indicator does not come on during the test-drive, but troubleshooting is done based on the DTC, check for poor connections or loose terminals at all connectors related to the circuit that you are troubleshooting.
- After the troubleshooting or repairs are done, clear the DTCs, and test-drive the vehicle under same conditions as when the DTC was originally set. Make sure the adaptive cruise control (ACC) indicator does not come on.
- The adaptive cruise control (ACC) system sometimes stops control because of the environment (weather, road conditions, driving conditions, etc.). A DTC may be stored in these cases.

DTCs that may be stored even when the system is normal:

DTC 83: Adaptive cruise control indicator (ACC) does not come on

Performance of the millimeter wave radar unit is not stable. (Driving behind a target vehicle that caused unstable reception.)

DTC 84: Adaptive cruise control (ACC) indicator does not come on

Target vehicle comes closer than the millimeter wave radar unit detecting limits (The target vehicle brakes suddenly, etc.).

DTC 85: Adaptive cruise control (ACC) indicator does not come on

Extensive driving on a rough road or a winding road, or VSA system detects problem.

DTC 86: Adaptive cruise control (ACC) indicator does not come on

Abnormal tire pressure, flat tire.

DTC 87: Adaptive cruise control (ACC) indicator does not come on

Adaptive cruise control (ACC) brake works continuously, or adaptive cruise control (ACC) brake control is temporarily prohibited by a communication line error detected between the adaptive cruise control (ACC) unit and VSA modulator-control unit.

DTC 88: Adaptive cruise control (ACC) indicator does not come on

Millimeter wave radar unit temperature is high, millimeter wave radar unit supply voltage is low, or out of detection area.

DTC 89: Adaptive cruise control (ACC) indicator does not come on

Front wheel spin

DTC 91: Adaptive cruise control (ACC) indicator does not come on

Vehicle skidded, spun out, or abrupt steering wheel movements.

DTC 93: Adaptive cruise control (ACC) indicator does not come on

Target vehicle comes closer than the millimeter wave radar detecting limits.

DTC 94: Adaptive cruise control (ACC) indicator does not come on

Rear tire problem (different diameter of tires, flat tire, or large air pressure differential).

DTC 95: Adaptive cruise control (ACC) indicator does not come on

Power supply voltage is too high.

DTC 96: Adaptive cruise control (ACC) indicator does not come on

Power supply voltage is too low.

DTC 99: Adaptive cruise control (ACC) indicator does not come on
Detects acceleration or deceleration that is out of the normal system operating range.

DTC 100: Adaptive cruise control (ACC) indicator does not come on

CMBS initial check is incomplete.

DTC 101: Adaptive cruise control (ACC) indicator does not come on

Rear wheel locked (driving with the parking brake applied, or the parking brake stuck).

DTC 107: Adaptive cruise control (ACC) indicator comes on

Millimeter wave radar unit aiming is incomplete.

Adaptive Cruise Control (ACC) System Inputs And Outputs:

Adaptive Cruise Control (ACC) System Inputs and Outputs