Common Issues with Adaptive Cruise Control on Mercedes-Benz C-Class W206 (2021-2024)

Adaptive Cruise Control (ACC) is a sophisticated system designed to enhance driving comfort and safety. However, like any advanced technology, it can encounter issues. Below are common problems, symptoms, diagnostic steps, tools required, and repair instructions for the ACC in the Mercedes-Benz C-Class W206.

Common Issues and Symptoms

1. ACC Not Engaging

   • Symptoms: The ACC system does not activate when the button is pressed. The cruise control light may also be absent on the dashboard.

2. Erratic Speed Control

   • Symptoms: The vehicle accelerates or decelerates unexpectedly, or it fails to maintain a constant speed.

3. Braking or Acceleration Issues

   • Symptoms: The car brakes or accelerates suddenly without driver input, or the system fails to respond to the vehicle ahead.

4. Camera or Sensor Malfunctions

   • Symptoms: Warning messages on the dashboard regarding the front radar or camera system. ACC may disengage unexpectedly.

5. Faulty Steering Wheel Controls

   • Symptoms: Buttons for ACC on the steering wheel do not respond.

Diagnostic Steps

Step 1: Visual Inspection

• Tools Required: Flashlight, OBD-II Scanner
• Instructions:
  • Inspect the radar sensor located in the front grille for any obstructions (dirt, debris, ice).
  • Check the windshield area for any cracks or damage near the camera sensor.
  • Examine wiring harnesses connected to the ACC system for any signs of wear or damage.

Step 2: OBD-II Diagnostic Scan

• Tools Required: OBD-II Scanner
• Instructions:
  • Connect the OBD-II scanner to the vehicle's diagnostic port.
  • Check for any trouble codes related to the ACC or related systems (e.g., radar sensor, camera).
  • Note any codes, especially those starting with C (chassis codes).

Step 3: System Reset

• Tools Required: OBD-II Scanner
• Instructions:
  • If codes are present, clear them using the OBD-II scanner.
  • Test the ACC function after clearing codes to see if the issue persists.

Step 4: Test Drive

• Instructions:
  • Take the vehicle for a test drive to evaluate the ACC's functionality.
  • Monitor for any warning messages or unusual behavior while engaging ACC.

Repair Instructions

Repair for ACC Not Engaging

1. Software Update

   • Tools Required: Star Diagnostic Tool
   • Instructions:
     • Use the Star Diagnostic Tool to check for software updates in the ACC module.
     • Follow manufacturer instructions to perform any available updates.

2. Inspect and Replace Switch

   • Tools Required: Screwdriver set, Multimeter
   • Instructions:
     • Remove the steering wheel cover to access the ACC switch.
     • Use a multimeter to test the switch for continuity.
     • If the switch is faulty, replace it with a new one.

Repair for Erratic Speed Control

1. Sensor Calibration

   • Tools Required: Star Diagnostic Tool
   • Instructions:
     • Connect the Star Diagnostic Tool and navigate to the ACC module.
     • Perform sensor calibration following the tool's prompts.

2. Radar Sensor Replacement

   • Tools Required: Socket set, Torque wrench
   • Instructions:
     • Remove the front grille to access the radar sensor.
     • Disconnect the wiring harness and remove the mounting bolts.
     • Install the new radar sensor, reconnect the harness, and reassemble the grille.

Repair for Braking or Acceleration Issues

1. Check and Clean Sensors

   • Tools Required: Cleaning cloth, Isopropyl alcohol
   • Instructions:
     • Clean the radar and camera sensors with a soft cloth and isopropyl alcohol to remove any grime that could interfere with operation.

2. Inspect Brake Pedal Sensor

   • Tools Required: Multimeter
   • Instructions:
     • Test the brake pedal position sensor for proper operation.
     • Replace the sensor if it is not functioning correctly.

Repair for Faulty Steering Wheel Controls

1. Inspect Wiring

   • Tools Required: Multimeter, Screwdriver set
   • Instructions:
     • Remove the steering wheel airbag and inspect the wiring harness connected to the ACC buttons.
     • Repair any damaged wires or connections.

2. Replace Steering Wheel Control Module

   • Tools Required: Socket set
   • Instructions:
     • Remove the steering wheel and replace the control module if the buttons are still unresponsive after checking connections.

Conclusion

The Adaptive Cruise Control system in the Mercedes-Benz C-Class W206 is essential for safe and comfortable driving, but issues can arise. Following the outlined diagnostic steps and repair instructions can help you identify and resolve these problems effectively. Always refer to the manufacturer’s service manual for specific details and torque specifications. If problems persist, seeking assistance from a qualified Mercedes-Benz technician is recommended.