Front radar sensor blocked

Radar should be right here...

 

Sometimes heavy rain, snow/slush, or too many bugs will block the radar sensor of the OnGuard system, causing the issue you describe. I've experienced this a few times. If it is caused by rain, then when the rain lets up you can stop, turn off the truck, and when you turn it back on the system should function as normal. With snow/slush, I've had to stop and clean it off before. However, if you are traveling in messy weather it can prove to be an exercise in futility because it just get's blocked again. I've also had it occur when the unit did not appear to be dirty or blocked by anything obvious.

Having said all of that, you can override the system so that you can still use the cruise control. You turn the cruise on/off three times and then when you turn it on the 4th time you set the speed. The cruise will function normally but you will not have access to the other features of the OnGuard system (collision avoidance, warning for following distance, speed of vehicle ahead, etc.) A word of caution on this though: if a driver is over-reliant on the OnGuard system to beep for insufficient following distance or routinely allows it to decelerate automatically when approaching slower traffic, this could lead to an accident. Common sense and prudent driving habits would deem the OnGuard system unnecessary, but it is worth noting because a distracted driver who is used to the system taking over could be right up on someone while subconsciously waiting on the OnGuard to do its thing.

 

Buzz strips on the sides of the road can knock it out too if you ride to long on them.

 

Huh... A day ago, wasn't it you? Had this whole trucking thing figured out? Lol.