Mercedes Collision Prevention Assist Plus Inoperative Message

Mercedes Benz Collision Prevention Assist Plus Inoperative

The warning error message “Collision Prevention Assist Plus inoperative” indicates that the collision prevention feature is no longer functioning and the vehicle will not detect potential collisions or automatically activate the brakes. COLLISION PREVENTION ASSIST PLUS in the Mercedes-Benz helps to reduce your risk of rear-ending another vehicle. Collision prevention may malfunction. The vehicle warns the driver by a warning message on the dashboard, stating, “Collision Prevention Assist Plus Inoperative See Owners Manual.”

Throttle response may become sluggish, and the car may feel like it has no power. This is a problem reported that can affect 2015 and newer Mercedes-Benz C-Class, GLS-Class, and E-Class owners. Collision assists malfunctions can be caused by something as simple as low battery voltage but can also indicate a faulty Engine Control Unit (ECU).

What does Collision Prevention Assist Plus Inoperative mean?

Error message Mercedes Collision Prevention Assist Plus, Inoperative See Owners Manual, means that the system has malfunctioned. The error message “Collision Prevention Assist Plus inoperative” is a warning that the car’s collision prevention system has ceased to operate. This means that the vehicle will no longer be able to detect potential collisions or automatically activate the brakes, reducing the level of safety and protection for the driver and passengers.

COLLISION PREVENTION ASSIST PLUS monitors the traffic in front of the vehicle. If it determines that you are about to hit another car, it will warn you with a message on the dashboard plus an audible sound. With collision assist disabled, your vehicle will no longer avoid a potential accident or automatically apply the brakes if you get too close to the vehicle in front of you.

Keep a safe distance from the vehicles in front of you and stay alert. If the warning happened only once and went away after restarting the vehicle, there may not be a reason to worry.


In most cases, you will experience one or two of these symptoms:

  • Collision Prevention Assist Plus Inoperative message
  • The vehicle loses power or won’t respond to the gas pedal.
  • The transmission gets stuck in limp mode.
  • The car won’t accelerate.
  • Brake Assist warning message on the dashboard.

Common Causes

Replace Battery on Mercedes-Benz GLK
  • Low temperatures: Extremely low or high outside temperatures can affect the system and cause it to malfunction.
  • Interference: You may get Collision Prevention Assist Plus Inoperative error if you drive near electromagnetic radiation sources, such as a radio station.
  • Battery Voltage: This message may come up if the voltage is too low. For example, if you turn off the engine but keep the ignition on while parked. Once you restart the car, you may be greeted with Collision Prevention Assist Plus Inoperative error message. Keeping the vehicle idle or driving for about 30 minutes should charge the battery and reset this warning.
  • Sensors: Sensors mounted at the front of the vehicle may stop working correctly if excessive dirt is at the front.
  • Engine Control Unit: Poor Engine Control Unit (ECU) connections due to loose, dirty, or overspray pins can cause communication issues with the accelerator pedal (gas pedal), proximity sensors, and throttle actuator contacts. This may be the problem if a vehicle is scanned with a Mercedes STAR scanner, and fault codes are stored for implausible data or communication.

Fix Collision Prevention Assist Plus Inoperative

While getting this error once a year may not be a concern, you want to get the system diagnosed if the Collision Prevention Assist Plus Inoperative error keeps coming up periodically.

Turn off then Restart Engine

Restart vehicle to reset Mercedes Collision Prevention Assist Plus Inoperative See Owners Manual

Find a safe location. Pull over, turn off the ignition, wait 2 minutes, and restart the vehicle. If the battery is partially discharged, you may need to let the car idle for at least 15 minutes before resetting the error.

Distance Sensors

radar sensors Mercedes Collision Prevention Assist Plus Inoperative See Owners Manual

Inspect the front bumper for excessive dirt or ice. Clean the bumper by removing any dirt on the bumper or on the cross member that is mounted near the radiator.

Update Software

Ask the dealer to perform a software update for the Collision Prevention Assist Module. Locate a Mercedes-Benz dealer near you. Call them and provide your VIN.

The dealer can tell you if a software update can fix your Collision Prevention Assist Plus Inoperative problems. If your dealer cannot help, consider filing a complaint with the National Highway Traffic Safety Administration (NHTSA).

Diagnose Collision Assist Module


To diagnose this problem further, you will need a scanner to read and clear Mercedes-Benz’s specific fault codes. The YOUCANIC Full System Scanner can read and clear all control modules of the Mercedes-Benz.


What does it mean when your Mercedes-Benz says inoperative?

Inoperative typically means that a particular feature or system in the Mercedes is not functioning properly. This could refer to various components, such as an audio system, a navigation system, or a climate control system. If your Mercedes displays an “inoperative” message, it may indicate a problem that needs to be addressed. It is recommended to have the car inspected by a qualified Mercedes-Benz technician to diagnose and resolve the issue.

What does collision prevention assist plus mean on a Mercedes?

COLLISION PREVENTION ASSIST PLUS provides peace of mind through its use of radar technology to detect potential collisions. The system alerts you if a vehicle or a stationary object is detected ahead and requires hard braking to avoid impact.

How do I get rid of collision prevention assist plus inoperative?

Allowing the car to stay turned off for 10-15 minutes can often restore power to the system. If the restart fails, inspect the front bumper where the sensors are located. If dirt or ice is blocking the sensors, clean the area and restart the car to enable the sensors to detect the road again. The next step would be to run a full system scan with a YOUCANIC scanner.

Does my Mercedes-Benz have collision prevention assistance?

You can verify if your Mercedes-Benz has collision prevention assistance by calling the dealer. The following models are known to have collision prevention assist.

C-class W205 Saloon Sedan
C-class S205 Estate
C-class A205 Convertible Cabriolet
C-class C205 Coupe
C Class C180 C200 C220 BlueTec C250 C300 C350e C400 4MATIC C450 C43 C450 C63 AMG
SL R231 SL450 SL550 SL63 AMG
CLS W218 C218 CLS550 CLS63 AMG
SLK R172
CLA C117 Coupe X117 Shooting Brake
CLA220d CLA250 CLA45 AMG
GLC X253 C253 W253 Hatchback Coupe
GLC GLC300 GLC350e GLC220d GLC 220d GLC250d GLC350d GLC300 4 MATIC GLC43 GLC63 AMG
GLA X156 GLA220d GLA250 GLA45 AMG
GLS X166 GLS450
AMG GT C190 R190
ML C292 Coupe
GLE350 GLE400 GLE550e GLE43 GLE63 AMG
B-class W242 W246
A-class W176
A class W177 Sedan Saloon Hatchback
A160 A160d A180 A180d A200 A200d A220 A220d A250e A35 A45 AMG 4MaticS-class W222 Saloon Sedan
S-class C217 Coupe
S-class A217 Convertible Cabriolet
S class S350 S400 Hybrid S500 S600 S300 BlueTEC S350 4Matic S550 S63 AMG, S65 AMG
E-class W212 S212 A207 C207 Facelift 2014 2015 2016 2017
E-class W213 S213 2016, 2017, 2018, 2019
E-class Coupe C238 2016, 2017, 2018, 2019
E-class Convertible A238 2017, 2018, 2019
E-class E200 E250 E300 E350e Hybrid E400 E450 E200d E220d E300d E350d E400d 4MATIC E43 AMG
CLS Class Coupe C257 2018, 2019
G Class W463 2018, 2019

These are only a few examples of vehicles that may be equipped with collision prevention assist plus. On some models, this system was optional.


  • Rushit Hila • ASE Certified

    Rushit Hila, an ASE-certified engineer (G1 Automotive Maintenance and Repair), brings over two decades of hands-on experience in the automotive world to his writing. With a strong educational background, including a Master of Science in Engineering and a Bachelor of Science in Engineering, he has honed his skills and expertise through years of practical work. As a respected authority in the field, Mr. Hila is dedicated to offering insightful and valuable content that resonates with both vehicle owners and mechanics.

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