Solving the Mercedes Collision Prevention Assist Plus Inoperative Issue in a Mercedes-Benz CLS 550
Collision Prevention Assist Plus is a crucial safety feature in modern vehicles, designed to help prevent accidents by alerting drivers to potential collisions and automatically applying the brakes if necessary. However, when this system becomes inoperative, it can compromise the safety of the vehicle and its occupants. In this article, we explore a real-world case study of a 2016 Mercedes-Benz CLS 550 4MATIC with an inoperative Collision Prevention Assist Plus system and the steps taken to resolve the issue.
Why is my Mercedes Collision Prevention Assist Plus not working?
Case Study Background : Mercedes Collision Prevention Assist Plus Inoperative
A 2016 Mercedes-Benz CLS 550 4MATIC was brought to our shop with a host of problems. The most pressing issue reported was the inoperative Collision Prevention Assist Plus system. The previous mechanic had replaced several components, including the ESP (Electronic Stability Program), ECU/control unit, and speed sensors, but the problem persisted.
Diagnosis Process
Given the extensive list of components already replaced, we decided to start our diagnosis by focusing on the ESP system. The ESP is critical as it monitors the vehicle’s speed and stability. Upon closer inspection, we discovered that the speed sensors previously installed were not original parts. These non-original sensors were providing incorrect values, even when the vehicle was stationary.
To resolve this, we replaced both front speed sensors with genuine Mercedes parts. After the replacement, the erroneous values returned to zero, as expected, indicating that the speed sensors were now functioning correctly.
Tracing Collision Prevention Assist Issue
With the speed sensor issue resolved, we shifted our focus to the Collision Prevention Assist system. We conducted a thorough inspection of the system, checking for any visible damage, wire melting, bridged connections, or water damage to the connectors. However, we found no issues in these areas.
Next, we decided to check the auxiliary battery, which controls the ECO Start/Stop function. We discovered that the auxiliary battery had a voltage of only 0.47 volts. This low voltage had caused the FRONT SAM (Signal Acquisition Module) to have a short circuit to ground. The auxiliary battery was essentially dead, likely for years, which explained the persistent issues with the Collision Prevention Assist system.
Solution Implementation
To address this, we replaced the auxiliary battery with a new one. After the replacement, we reset the system and performed a series of tests to ensure that all related systems, including the Collision Prevention Assist Plus, were functioning correctly. The system was now operational, and the vehicle was ready to be returned to the owner.
Conclusion
This case study highlights the importance of using original parts and performing thorough diagnostics when dealing with complex automotive systems. The initial replacement of non-original speed sensors led to incorrect readings and a misdiagnosis of the problem. Additionally, the auxiliary battery’s condition was a critical factor that had been overlooked.
Mercedes collision prevention assist plus sensor location
The Collision Prevention Assist Plus system in a Mercedes typically uses a combination of radar sensors and cameras to monitor the vehicle’s surroundings. Here are the locations of the key sensors:
- Radar Sensor: The primary radar sensor is usually located behind the front grille or bumper. It is positioned centrally to provide a wide field of view and detect obstacles and vehicles ahead.
- Camera Sensor: There is often a camera mounted behind the windshield, near the rearview mirror. This camera works in conjunction with the radar sensor to provide visual data and assist with features such as lane-keeping and traffic sign recognition.
- Additional Sensors: Depending on the specific model and configuration, there may be additional radar sensors located in the corners of the front bumper. These sensors help with detecting vehicles and obstacles in adjacent lanes, improving the system’s overall performance.
These sensors work together to continuously monitor the vehicle’s surroundings and provide real-time data to the Collision Prevention Assist Plus system. Proper maintenance and calibration of these sensors are crucial for the accurate functioning of the system.
Mercedes collision prevention assist plus inoperative reset
Resetting the Collision Prevention Assist Plus system in a Mercedes-Benz vehicle often involves a combination of checking and addressing underlying issues and performing a system reset using diagnostic tools. Here are the steps to reset the system:
Step-by-Step Guide to Resetting Collision Prevention Assist Plus
1. Check for Underlying Issues
- Inspect Sensors: Ensure that all sensors (radar and camera) are clean and free from obstructions.
- Check Wiring and Connectors: Look for any signs of damage, corrosion, or loose connections in the wiring and connectors associated with the Collision Prevention Assist Plus system.
- Battery Health: Verify that both the main and auxiliary batteries are in good condition. A low battery voltage can cause the system to become inoperative.
2. Perform a Diagnostic Scan
- Diagnostic Tool: Use a Mercedes-Benz-specific diagnostic tool, such as Xentry or STAR Diagnostic, to scan for fault codes related to the Collision Prevention Assist Plus system.
- Interpret Codes: Review and interpret any fault codes to identify specific issues that need to be addressed.
3. Address Identified Issues
- Replace Faulty Components: If the diagnostic scan reveals any faulty components, such as speed sensors, radar units, or control modules, replace them with genuine parts.
- Clear Obstructions: Ensure that all sensors have a clear line of sight and are not obstructed by dirt, snow, or other debris.
4. Reset the System
- Using Diagnostic Tool: With the diagnostic tool connected to the vehicle, navigate to the Collision Prevention Assist Plus system and perform a reset or reinitialization.
- Follow Instructions: Follow the on-screen instructions provided by the diagnostic tool to complete the reset process.
5.Test the System
- Road Test: Conduct a road test to verify that the Collision Prevention Assist Plus system is now functioning correctly.
- Monitor for Alerts: During the road test, monitor the dashboard for any alerts or warnings related to the system.
Conclusion
Resetting the Collision Prevention Assist Plus system requires a methodical approach to identify and address any underlying issues. By ensuring that sensors, wiring, and batteries are in good condition and using a diagnostic tool to perform the reset, you can restore the functionality of this critical safety feature.