Auto Stop-Start System No Longer Working - Before You Jump For Joy, Here Are the Likely Causes, and Why You Need to Have the Car Looked At Right Away

If you like auto stop-start in your car, raise your hand. OK, can we all agree that this is a universally despised “feature” of cars that nobody asked for and everyone would love to shut off permanently? Well, mine quit this week, and I was at first pretty psyched that it did. No more hassles at stop signs, no more having to shut it off manually. Then I did a bit of research and found out what can cause the auto stop-start to quit. The news is not good.

What Causes Auto Stop-Start To Stop Working
There are a number of reasons that auto stop-start can quit working. Many of the reasons are simply part of the system’s normal programming. Let’s explore those first. Because the system discontinues the engine operation, auto stop-start will often refrain from operating on its own when running the engine is needed for various reasons. Here’s a quick punch list of those normal scenarios.

Auto Stop-Start and Cold Temps
If it is very cold outside, your car’s auto stop-start system will often not operate. This is because the car is still warming up, and the HVAC system needs that heat to warm the cabin. So, auto stop-start temporarily holds off on operating under this scenario. It’s normal.

In addition, auto stop-start may pause when temperatures are below around 32°F. The vehicle may need the engine to operate to maintain its heating ability. So, even after the car has “warmed up,” auto stop-start may not operate in colder temps. Again, this is normal.

Auto Stop-Start - Certain Vehicle Positions
In addition to cold temps, your auto stop-start may stop working if the vehicle is at an odd angle or if the steering wheel is turned sharply while you are stopped. This is a normal situation. Not a fault with the system.

Auto Stop-Start - High Electrical Load
If you are running everything at once, such as wipers, headlights, HVAC fan, glass defrosters, heated seats and steering wheel, infotainment, and other power draws, the auto stop-start system may pause its normal functioning because it is programmed not to deplete your battery. This is normal, and it will resume when the load is less.

Auto Stop-Start - Safety Interlocks
There are also a number of safety interlocks that prevent auto stop-start from operating temporarily. Here’s a quick list of things that temporarily disable the auto stop-start system.
 - The driver's seatbelt is unfastened.
 - A door or the hood is open.
 - The transmission is in a gear other than  - Drive (D) (or neutral for manuals).
 - Insufficient brake pedal pressure in an automatic vehicle.
 - The vehicle has not reached a minimum speed since the last stop.

Auto Stop-Start - Problem With Your Battery
The biggest concern when your car’s auto stop-start suddenly ceases operation without any of the causes above is that your vehicle’s charging system or battery is not working properly. This can simply be the battery aging and reaching its end of life, or it could mean the alternator or other charging components are failing. This is why we say, “don’t jump for joy yet.” When my auto stop-start system stopped working, this was one of the causes. AAA tested my battery and found it was not holding sufficient charge for auto stop-start to operate. At just 45%, it was too low. I needed a new battery.

A Ford Bronco Sport owner named Howard M. posted this help request in a Facebook group that I found to be very helpful when my auto start-stop system ceased operating. He asked,

Advertising

Who is having issues with the stop/start system working?  I tried using the control button, but nothing happened.  Is it due to the battery? I own a 2024 Bronco Sport Badlands 2.0L.

Auto Stop-Start - Coolant System Failure or Problems
Another reason that auto stop-start can cease is if the “cooling” system is having some sort of trouble. Coolant is also “heatant” if you think about it. If the system is not allowing the car to warm up properly, auto stop-start will not operate. A failing water pump, a leaking hose or radiator, or a lack of coolant can all cause the auto stop-start to pause its operation.

Auto Stop-Start - There Is Hope That the Dumb Mandate Will Be Removed From New Cars
The latest news on auto stop-start may not help those who already have a system, but your next new vehicle may not require it be on with every startup. U.S. Environmental Protection Agency (EPA) Administrator Lee Zeldin, under President Trump, has said that the agency will not require it to auto-reset on future cars. Hopefully, a permanent “OFF” setting will be part of future vehicle designs. Zeldin posted on X:

Start/stop technology: where your car dies at every red light, so companies get a climate participation trophy. EPA approved it, and everyone hates it, so we’re fixing it.

Auto Stop-Start - What To Do If It Fails
If your auto stop-start system stops operating and the car is warm, temperatures are above 40°F, and the vehicle has been warmed up, take note of whether it works after a long drive. If it does not, you should first check that you have coolant. Refer to your owner's manual for instructions on how to check it. Next, have your battery and charging system tested. Finally, bring the vehicle in for service. Although nobody likes auto stop-start, we generally like an unexpected breakdown a lot less.

Have you had your auto stop-start cease operation unexpectedly? Tell us your experience in the comments section below. 

Hat tip to the Facebook Ford Bronco Sport Group on Facebook, members of which contributed insights to the story. 

John Goreham is the Vice President of the New England Motor Press Association and an expert vehicle tester. John completed an engineering program with a focus on electric vehicles, followed by two decades of work in high-tech, biopharma, and the automotive supply chain before becoming a news contributor. He is a member of the Society of Automotive Engineers (SAE int). In addition to his fourteen years of work at Torque News, John has published thousands of articles and reviews at American news outlets. He is known for offering unfiltered opinions on vehicle topics. You can connect with John on LinkedIn and follow his work on his personal X channel or on our X channel. John employs grammar and punctuation software when proofreading, and he sometimes uses image generation tools.