Adaptive Cruise Control problems of the 2015 Ford Mustang

Hi, I was driving on the freeway and suddenly my car stopped accelerating. I would push the acceleration pedal but it wouldnt speed up. And for a few times it would speed up very much. This was very rapid fluctuation. I also noticed that the cruise control was not working. This was very scary being on the highway with this kind of speed fluctuation. After I came back home, I noticed that the brake light wouldnt turn off at all. After doing some research I found that the brake light switch broke and the car was sensing that the brake was being applied and hence was doing acceleration fluctuations. I also found out that there are many other same vehicles which has the same issue.

The contact owns a 2015 Ford Mustang. The contact stated that the vehicle was repaired under NHTSA campaign number: 22v011000 (service brakes, hydraulic); however, while driving with the cruise control activated, the brake pedal was depressed but instead the vehicle accelerated and failed to stop as needed. The contact stated that an excessive amount of pressure was needed to depress the brake pedal while stopping the vehicle. The contact stated that the failure only occurred while the cruise control was activated. The contact had taken the vehicle to the dealer and the mechanic was also able to duplicate the failure. The dealer diagnosed that the cruise control had malfunctioned and caused the brakes to not operate as needed to deactivate the cruise control. The dealer replaced the cruise control switch; however, the failure persisted. The manufacturer was not made aware of the failure. The approximate failure mileage was 54,000.

Rubber stopper on brake sensor dry rotted and broke off. This caused the car to think I was applying the brakes when I wasn’t. It would cut the throttle while trying to maintain speed and my brake lights were always on even though I wasn’t touching the brakes or in the car for that matter.

Traveling on highway using cruise control at posted speed limit. Approached slowdown due to accident and applied brakes. Accelerated to limit (manually) after passing accident. I was in middle lane. Vehicle abruptly began to decelerate. Continuous pressure on gas pedal did not increase speed, so I put on hazards and moved to slow lane. No failures on dashboard and quick scan through gages did not identify an issue. Re-applied pressure to gas pedal wanting to get to next exit. Car sped up, but when approaching 50 mph, it decreased again. Found that pumping gas would allow me to maintain highway speed. Pulled into truck stop at exit and turned car off. Message on console "hill start assist not available". Let vehicle rest 15 minutes, added gas. Quick web search seemed to point to problem with abs sensor. Seemed to drive ok in parking lot and road leading to highway ramp. Decided to try to get closer to home. Problem occurs immediately after climbing to 50 mph. Cruise control won't work. By carefully monitoring speed and pumping gas into overdrive when needed, I was able to get home. Could not get appointment with dealership until late afternoon next day. Hill start assist message comes on again when stopping. After arriving home and parking in garage I went inside for about 30 minutes. Needed to unload items from car and went back to garage noticing that the strip of lights above trunk are still on. Got back in car, started it (got hill assist message), turned lights on/off and turned off car. Now my rear brake lights are also on. I had seen a post about this, so unhooked battery to prevent drain. Next morning, reattached battery and had same problem. After more internet investigation, awesome humans who have also had this dangerous issue and provided a $5 fix instead of a $500+ dealership fix. . Read more...