How To Disable Collision Mitigation System On Kenworth T680

The Collision Mitigation System (CMS) on a Kenworth T680 is designed to improve safety by monitoring road conditions and assisting with braking if a potential collision is detected. However, there are situations, such as specific maintenance procedures or driving in unusual conditions, where disabling the CMS temporarily becomes necessary. Disabling this system is not always straightforward and should be done with care, as it affects key safety features.

This guide explains when, why, and how you can disable the CMS on your Kenworth T680, as well as what to consider before doing so. Follow these steps carefully to ensure you make the right decision for your situation.

Understanding the Collision Mitigation System on Kenworth T680

The Collision Mitigation System in a Kenworth T680 typically uses radar and camera sensors mounted in the front grille or windshield area. The system monitors traffic ahead and can apply the brakes automatically to help avoid or reduce the severity of a collision. It also works in conjunction with adaptive cruise control and lane departure warning systems in many models.

Kenworth's CMS is often sourced from Bendix or WABCO (now ZF), and each may have slightly different setup and interface methods. Standard features include forward collision warning, active braking, and sometimes lane-keeping alerts. Before you attempt to disable the system, identify which CMS version your truck uses by checking the owner’s manual or looking for a sticker on the dashboard or fuse panel.

Reasons Drivers Might Need to Disable the CMS

Most of the time, it’s best to leave the CMS active, but certain scenarios call for temporarily turning it off. Some common examples include when the system is giving false positives, such as detecting phantom obstacles in heavy rain, snow, or fog. This can cause unnecessary emergency braking, which might be dangerous in slick conditions or heavy traffic.

Occasionally, you might need to disable the CMS when taking the vehicle through a truck wash, performing certain types of maintenance that involve the front sensors, or when towing or pushing equipment that could interfere with the radar. Fleet managers sometimes need to deactivate the system during diagnostics, software updates, or calibration procedures.

Precautions Before Disabling the Collision Mitigation System

Disabling the CMS removes a major safety net designed to protect you and others on the road. You’ll lose automatic emergency braking and forward collision alerts, so extra vigilance is required. If your company or state regulations mandate the use of active safety systems, disabling the CMS may not be allowed except for maintenance by qualified personnel.

Always consult the owner’s manual and check with your fleet safety manager or dealer before proceeding. Disabling the system could also leave a fault code in the onboard diagnostics or trigger dash warning lights. Document any changes you make and restore the system as soon as possible after your procedure is complete.

Step-by-Step: Disabling the CMS via Dash Controls

On most Kenworth T680s equipped with CMS, you can temporarily disable collision mitigation via the dashboard controls:

1. With the ignition On but the engine Off, locate the menu button or home button on the right side of your steering wheel or instrument panel.
2. Navigate through the Driver Information Display (DID) using the arrow keys until you find the Driver Assistance or Collision Mitigation menu.
3. Select the Collision Mitigation option. You’ll typically see a toggle for enabling or disabling the system, sometimes labeled as CMS Override or System Off.
4. Press the select or OK button to disable the system. A warning icon should appear in your display, confirming that CMS is off. Some systems may require you to hold the button for several seconds to confirm.

This method only disables the system until the next key cycle (turning the ignition Off and back On). For longer-term or permanent disabling, other steps are required.

Disabling the CMS Using Diagnostic Tools or Software

For extended deactivation or troubleshooting, you’ll need access to diagnostic tools compatible with your truck’s electronic control unit (ECU). This is usually done by a qualified technician, but some fleet owners use tools such as Bendix ACom Diagnostics or the Kenworth DAVIE4 software. You’ll need a laptop and a proper communication cable to connect to the truck’s OBD port.

1. Connect the diagnostic tool to the truck.
2. Turn the ignition On.
3. In the software, select the CMS or ABS module.
4. Look for an option to disable or set the CMS to Service Mode. Some tools call this Override or Deactivation.
5. Apply the changes and save your settings. The system may prompt for a password or authorization, especially if it’s a fleet vehicle.

Note that this method can leave the CMS disabled until it’s manually reactivated, which may trigger fault codes or affect other safety features. Only use this approach if absolutely necessary and allowed by your management or regulations.

Disabling the CMS by Disconnecting Sensors or Fuses

Some drivers consider physically disconnecting the CMS radar sensor or removing the fuse for the collision mitigation module. This method is not recommended for regular use but may be necessary during sensor replacement or if the system malfunctions and cannot be disabled electronically.

To do this, locate the fuse box (usually under the dashboard or in an exterior compartment) and check the diagram for the fuse labeled CMS, Collision Mitigation, or Bendix Wingman. Remove the fuse with a puller or pliers. If you need to disconnect the front radar sensor, unplug its wiring harness, usually found behind the front bumper or grille. Afterward, the system will be completely disabled, and a fault light should appear. Always reinstall the fuse and reconnect the sensor promptly to restore normal operations.

What Happens After Disabling the CMS?

With the CMS disabled, your Kenworth T680 will no longer automatically apply the brakes or warn you of impending collisions. You may see warning lights or messages in the driver information display. Adaptive cruise control features may also be affected, depending on your truck’s configuration. If you disabled the system via dash controls, it will typically reset to active the next time you start the truck. Disabling by fuse or diagnostic software can require manual intervention to restore.

Always verify that the system is working properly after reactivation by checking for warning lights and confirming sensor status using the dash menu or diagnostic tool. If you see persistent errors or the system won’t reactivate, consult a Kenworth dealer or qualified technician for further troubleshooting.

Re-enabling the Collision Mitigation System

Restoring CMS functionality is crucial for safe operation. If you disabled it via the dash, simply cycle the ignition or use the same menu path to toggle the system back on. For software-based disables, connect your diagnostic tool and follow the prompts to reactivate the system, then clear any related fault codes.

If you removed a fuse or disconnected a sensor, replace the fuse and reconnect the harness, then cycle the ignition. Some systems may require calibration or a test drive to reset properly. If warning lights persist, a diagnostic scan is usually needed to clear any stored errors. Always verify CMS operation by checking the dash display and confirming you receive forward collision alerts during a test drive.

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