Initial Inspection and Diagnostic Overview
How to Troubleshoot the Adaptive Cruise Control (ACC)
ACC Indicator (Amber)
When the ACC system is OK, the ACC indicator comes on for about 2 seconds after pressing the engine start/stop button to select the ON mode, then it goes off.
When the ACC system detects a problem while in operation, the ACC system stops control, and the ACC indicator changes from green to amber and stays on.
NOTE: The ACC system is communicating with the PCM, the VSA system, and the gauge control module by F-CAN. If a connected unit malfunctions, the ACC system will not operate. In this case, both the ACC indicator and the connected unit indicator come on and stay on (except the gauge control module).
ACC Activation Indicator (Green)
When the ACC system is OK, the indicator comes on when the MAIN switch is ON, and goes off when the MAIN switch is OFF. If the ACC system detects any malfunctions, the indicator color changes from green to amber, and stays on.
Self-Diagnostic Function
The ACC system has a self-diagnostic function. If the self-diagnostic function detects a malfunction, the ACC system stops control, turns on the ACC indicator (amber), and stores DTCs.
Multi-Information Display (MID) Indication
When the ACC system is OK, the ACC indicates its operation on the multi-information display (MID) when the MAIN switch is ON.
ACC Unit
The ACC unit uses input from the millimeter wave radar to control the vehicle's speed and brakes to maintain a constant distance between the vehicle and other moving vehicles directly ahead.
Millimeter Wave Radar
The millimeter wave radar calculates the distance between the moving vehicle ahead and your vehicle, and detects the two vehicles' speed differential.
The ACC unit receives this information from the millimeter wave radar.
The millimeter wave radar also has an error detection function, and it sends a signal to the ACC unit if an error is detected.
CAN Communication
The ACC unit is on the F-CAN, and it communicates with other units (AcuraLink, Gauge control module, Steering angle sensor, PCM, SH-AWD, SRS, E-pretensioner unit, ADS, TPMS, Yaw rate-acceleration sensor, and VSA) via the F-CAN.
If the ACC unit detects a communication error or a malfunction in another connected unit, the ACC system will not operate even though it is OK.
In this case, both the ACC indicator (amber) and the related unit indicator will come on and stay on.
Millimeter Wave Radar Aiming
If the millimeter wave radar is removed or replaced, do the millimeter wave radar aiming procedure. If the aiming is incomplete, the ACC indicator comes on.
How to Troubleshoot DTCs
Check the DTCs with the HDS. Make a copy of the freeze data, then clear the DTC.
Before troubleshooting, check and note these items:
- Ask the client about the conditions when the problem occurred, and try to reproduce the same conditions for troubleshooting.
- If the symptom does not appear and the 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 the same conditions as when the DTC was originally set. Make sure the ACC indicator does not come on.
- The ACC system sometimes stops control because of the environment (weather, road conditions, driving conditions, etc.). A DTC may be stored in these cases.
DTCs may be stored even when the system is OK:
NOTE: The ACC indicator does not come on when the following DTCs are stored (except DTC 199: ACC unit Programming Error).
DTC 83: Millimeter Wave Radar Detection Unstable
Driving behind a target vehicle that caused unstable reception.
DTC 84:Target Vehicle Comes Closer Than the Millimeter Wave Radar Detecting Limits
The target vehicle brakes suddenly, etc.
DTC 85: Extensive Driving on a Rough or Winding Road, or VSA System Malfunction
DTC 86:Abnormal Tire Pressure
Abnormal tire pressure, flat tire.
DTC 87:ACC Brake Control Temporarily Prohibited
The ACC brake works continuously, or ACC brake control is temporarily prohibited by a communication line error detected between the ACC unit and VSA modulator-control unit.
DTC 88:Millimeter Wave Radar Out of Detection Condition
The millimeter wave radar temperature is too high, the millimeter wave radar supply voltage is too low, or out of detection condition.
DTC 89: Front Wheel Spin
DTC 91: Vehicle Skidded, Spun Out, or Abrupt Steering Wheel Movements
DTC 93:Front Tire Problem
Different diameter tires, flat tire, or large air pressure differential.
DTC 94:Rear Tire Problem
Different diameter tires, flat tire, or large air pressure differential.
DTC 95: Power Supply Voltage Too High
DTC 96: Power Supply Voltage Too Low
DTC 99: Acceleration/Deceleration Abnormality
DTC 101: Rear Wheel Locked
Driving with the parking brake applied, or the parking brake stuck.
NOTE: Loose or poor connections are a common cause of intermittent DTCs and other symptoms. If your troubleshooting results in no trouble found, monitor the ACC, CMBS, and VSA data lists while flexing all the circuit connections between the various sensors and their control units. If any values change, you have found a poor connection.
How to Retrieve DTCs
NOTE: Make sure the battery is fully charged before you begin.
1. Press the engine start/stop button to select the OFF mode.
2. Connect the HDS (Honda Diagnostic System) to the data link connector (DLC) (A) located under the driver's side of the dashboard.
3. Press the engine start/stop button to select the ON mode.
4. Make sure the HDS communicates with the vehicle and the ACC unit. If it does not communicate, troubleshoot the DLC circuit Testing and Inspection.
5. Use the HDS to check for ACC DTCs.
6. Read and record the DTC.
7. Press the engine start/stop button to select the OFF mode, then wait for 10 seconds.
8. Disconnect the HDS from the DLC.
9. Do the troubleshooting procedure for the DTC.
How to Clear DTCs
NOTE: Make sure the battery is fully charged before you begin.
1. Press the engine start/stop button to select the OFF mode.
2. Connect the HDS (Honda Diagnostic System) to the data link connector (DLC) (A) located under the driver's side of the dashboard.
3. Press the engine start/stop button to select the ON mode.
4. Make sure the HDS communicates with the vehicle and the ACC unit. If it does not communicate, troubleshoot the DLC circuit Testing and Inspection.
5. In the DRIVING SUPPORT MENU of the HDS, select ACC, then DTCs choose the clear DTCs icon, and follow the prompts.
6. Press the engine start/stop button to select the OFF mode, then wait for 10 seconds.
7. Disconnect the HDS from the DLC.