What auto start does and why cars have it
Auto start — sometimes called remote start or push-button start — is a feature that lets you start your car's engine without turning a physical key or being inside the vehicle. You press a button on your key fob, a button on your dashboard, or use a smartphone app, and the engine turns on from a distance. The car warms up, the air conditioning or heat begins, and the windows or mirrors may defrost, all before you get in.
The main reason manufacturers added this feature is convenience and comfort. On a cold morning, you can start the engine while you finish getting ready indoors. In summer, you can cool the cabin before you sit down. For people with mobility challenges, remote start reduces the physical effort of getting into a cold or hot car. It also means your car is ready to drive when ready — no waiting for the engine to warm up once you're behind the wheel.
Auto start comes in two forms: factory-installed (built into the car when it was made) and aftermarket (added later by a shop or dealer). Factory systems are integrated into the car's computer and key fob. Aftermarket systems are separate devices wired into the ignition and starter, usually controlled by a separate remote or your phone.
Key Takeaways
- Auto start lets you turn on your engine from outside the car using a key fob button, dashboard button, or phone app, so the car is warm or cool before you enter.
- Factory auto start comes built into newer cars and is controlled by your original key fob, while aftermarket systems are added later and use a separate remote or app.
- Auto start will shut itself off after a set time (usually 10 to 20 minutes) to prevent the engine from running unattended for hours and wasting fuel.
- Some cars require you to press the brake pedal or turn the key to the "On" position within a few minutes of remote start, or the engine will shut down automatically.
- Aftermarket auto start systems can interfere with your car's computer or security features, so installation by a professional is important and may void your warranty.
How factory auto start differs from aftermarket systems
Factory auto start is engineered by the car manufacturer and integrated into the vehicle's electrical and computer systems from the assembly line. It uses your original key fob — the same one that locks and unlocks the doors — and communicates directly with the car's engine control module. When you press the remote start button, the car recognizes the signal, disables the steering wheel lock, and cranks the engine. Factory systems are reliable because they're designed specifically for that car's engine and transmission.
Aftermarket auto start is a third-party device installed by a dealer, car alarm shop, or independent mechanic after you buy the car. It's wired into the ignition switch, starter motor, and sometimes the car's data bus (the network that lets different computer modules talk to each other). Aftermarket systems come with their own remote control or connect to your smartphone. They're cheaper to install than buying a car with factory auto start already included, but they require more wiring and can sometimes conflict with the car's original security or computer systems.
The choice between them usually depends on what your car came with. If your car has factory auto start, use it — it's the safest option. If you want to add auto start to an older car that doesn't have it, an aftermarket system is your only choice, but have it installed by someone who knows your specific car model.
Safety features that prevent the engine from running unattended
Auto start systems include built-in limits to keep the engine from running indefinitely while nobody is in the car. The most common limit is a timer: the engine runs for a set period — usually 10 to 20 minutes, depending on the car — and then shuts off automatically. This prevents fuel waste and reduces emissions if you forget that you started the car remotely.
Many cars also require you to take an action inside the vehicle to keep the engine running past the timer. You might need to press the brake pedal, turn the steering wheel, or move the gear shift. Some cars require you to insert your key fob into the ignition or press the start button on the dashboard within a few minutes of the remote start. If you don't, the engine shuts down. This feature prevents theft: if someone steals your key fob and starts your car remotely, they can't drive away unless they can also get inside and complete the next step.
A few cars also have a range limit: remote start only works if you're within a certain distance of the vehicle, usually 300 feet to a quarter mile depending on the system. This is a security measure to prevent someone far away from starting your car.
When auto start won't work or will shut down
Auto start has several conditions that prevent it from working or cause it to stop. If your car is already running, you cannot remote start it — the button will do nothing. If the doors are unlocked, many systems won't start the engine as a security measure. If the hood is open or a door is ajar, the engine may not turn on or will shut down when ready.
Some cars disable remote start if the battery voltage is low, because starting the engine drains the battery and the system wants to make sure you can still start the car normally if needed. If you've lost your key fob or it's out of battery, you won't be able to use remote start, though you can still start the car the traditional way — with the key or push button inside.
In cold climates, some cars won't allow remote start if the outside temperature is below a certain threshold (often around -20°F), because the engine oil becomes too thick and starting it remotely could damage the engine. In very hot climates, some systems won't start if the interior temperature is above a certain point, to avoid running the air conditioning for too long and draining the battery.
What happens to your warranty if you add aftermarket auto start
Adding an aftermarket auto start system can affect your car's warranty, depending on what the warranty covers and how the system is installed. If the installation damages a component that's covered by warranty — for example, if wiring is cut incorrectly and it damages the dashboard — the manufacturer may refuse to cover that repair. Some manufacturers have a rule that any modification voids the entire powertrain warranty, while others only void coverage for the specific system that was modified.
Before you have aftermarket auto start installed, ask the shop whether they carry insurance that covers installation mistakes, and ask your car's manufacturer or dealer whether the installation will affect your warranty. Get the answer in writing. A professional installer who specializes in your car model is less likely to cause problems than a general shop, and they'll know which systems are compatible with your car's computer.
Fuel and battery drain from using auto start regularly
Using auto start does consume fuel and battery power, but the amount depends on how often you use it and how long the engine runs. Each remote start session burns a small amount of fuel — roughly the same as idling for 10 to 20 minutes. If you use remote start once a day on a cold morning, the fuel cost is minimal over a month. If you use it multiple times a day, the cost adds up.
The bigger concern for most people is battery drain. Remote start requires the battery to have enough charge to crank the engine, and if you use it frequently in very cold weather, the battery has to work harder. In extreme cold, a weak battery might not have enough power to both remote start the car and start it normally later if the battery dies. If your car's battery is old or weak, have it tested before relying on remote start in winter.
Modern cars manage this by monitoring battery voltage and disabling remote start if the battery is too low. If you see that remote start isn't working, it may be because the system detected that your battery needs to be preserved for a normal start.
Smartphone apps and remote start from a distance
Some newer cars come with a smartphone app that includes remote start, letting you start your car from anywhere you have a cellular signal — not just within range of a key fob. Examples include the OnStar app for General Motors vehicles, the FordPass app for Ford cars, and the MyBMW app for BMW. These apps use your car's built-in cellular modem to receive the command and start the engine.
Aftermarket systems also offer smartphone control, usually through a separate app provided by the installer. These systems use either cellular data or your phone's Bluetooth connection to communicate with the device installed in your car. The advantage is convenience — you can start your car from work or home. The disadvantage is that you depend on the app company's servers staying online, and if the company goes out of business or stops supporting the app, the feature may stop working.
Smartphone remote start has the same safety limits as key fob remote start: the engine runs for a set time and then shuts off, and many systems require you to take an action inside the car to keep it running. Check your car's manual or app to see what those limits are.
Frequently Asked Questions
Does auto start drain my car battery if I use it every day?
Regular use does draw power from the battery, but modern cars are designed to handle it. The bigger risk is in very cold weather, when the battery is already working harder. If your battery is old or weak, have it tested before winter. If remote start stops working, it usually means the system detected low battery voltage and disabled the feature to protect your ability to start the car normally.
Can I use remote start if my car is parked in a garage?
You can press the button, but the engine will start and then shut down within seconds or minutes because the car detects that it's in a closed space. Never let a car run in a garage — the exhaust contains carbon monoxide, which is deadly in enclosed spaces. Remote start is meant for outdoor parking only.
What if my key fob battery dies — can I still use remote start?
No. Remote start requires a functioning key fob to send the signal to the car. If the fob battery is dead, replace it with a new battery (usually a coin-cell battery available at any drugstore or electronics store for a few dollars). You can still start the car normally using the backup key or the push button on the dashboard.
Does remote start work if the car is locked?
Yes. Remote start is designed to work on a locked car — that's the whole point. The engine starts, but the doors remain locked until you unlock them with your key fob or the unlock button on the door handle. This is a security feature.
Will aftermarket auto start work with my car's security system?
It depends on the system and the car. Some aftermarket systems integrate smoothly with factory security, while others can cause conflicts — for example, the car might think it's being stolen and trigger the alarm. A professional installer who knows your specific car model can tell you whether the system is compatible and can install it correctly to avoid problems.