Reviewed: August 2026. We recheck this guide every 6 months.
A keyless, push-button car has two unrelated ways to leave you stuck. A dark, silent car with no dashboard lights has a flat 12V battery, the same failure any car can have, and it jump-starts the normal way with a jump starter or jumper cables. A car with working lights and locks that will not sense your fob has a flat coin cell inside the fob itself, and jump-starting will not help. Tell the two apart first.
Two problems, not one
It is easy to lump these together because both show up as "the car won't start," but they have nothing in common under the hood. A flat 12V battery means the car has no power for anything: no dashboard lights, no interior chime, no response when you press the brake or the start button. This is the same dead-battery problem every car has, keyless or not, and it is fixed the same way: by jump-starting the 12V battery. A flat fob coin cell is a completely different situation. The car itself is fully powered. Lights work, the doors unlock or lock with the physical buttons, but the car cannot detect the fob's signal to authorize a start, so pressing the start button does nothing or gives an error message about the key not being found.
How to tell which one you actually have
Before doing anything, check what the car is doing when you try to start it.
| What you see | Likely cause | What to do |
|---|---|---|
| No lights, no chime, no response to anything electrical | Flat 12V battery | Jump start the 12V battery |
| Dashboard lights work, doors respond, but start button gives a "key not found" message or does nothing | Flat fob battery | Try the fob-against-button method or the mechanical key blade |
| Dashboard lights work, but the car is otherwise completely unresponsive | Could be either; check your fob's indicator light or try a spare fob first | If a spare fob works, it is the original fob's battery; if not, treat it as a 12V battery issue |
If you are still unsure after checking these signs, treating it as a 12V battery problem first is the safer default, since jump-starting a car that turns out to only have a fob issue does no harm.
Jump-starting the 12V battery in a keyless car
Once you have confirmed it is a genuine 12V battery problem, the process is the same one used on any car: connect a portable jump starter or jumper cables from a second vehicle, get in with your working fob in your possession, and press the start button with your foot on the brake. The keyless system does not change the mechanics of jump-starting; it only changes how you authorize the start once power is restored. The clamp order, which terminal to connect first, and how long to wait matter more than the fact that the car has no physical ignition key, and we cover that full procedure separately in our step-by-step guide to using a portable jump starter safely. If you do not yet own a jump starter, our independent buyer's guide to choosing a portable jump starter walks through what actually matters when picking one, and our guide to how many amps of jump starter you actually need helps confirm a pack is genuinely sized for your engine before an emergency, not after. If you have neither tool yet, jump starter or jumper cables covers which one suits a driver who is often alone versus one who usually has help nearby.
Finding your car's jump terminals: why the owner's manual is the authority here
Many modern vehicles, including many keyless ones, do not have an easily reachable 12V battery under the hood. It may sit in the trunk, under a seat, or somewhere else the manufacturer chose for space or weight reasons. To handle this, many of these vehicles provide a remote positive jump terminal, sometimes under the hood even when the battery itself is elsewhere, sometimes in the engine bay marked with a small battery symbol, and sometimes described only in the manual's roadside-assistance section. We are not going to name a specific location here, because it genuinely varies by manufacturer and model, and a wrong guess risks a bad connection. Your owner's manual is the correct source for this, specifically the section usually titled "jump starting" or "roadside assistance." If you cannot find your manual, most manufacturers also publish it as a free PDF on their owner-support website, searchable by your vehicle's model and year.
If it's the fob battery: the hidden mechanical key blade
Nearly every keyless fob has a small mechanical key blade hidden inside it, usually released by a small button, latch, or sliding cover on the fob's body. This blade exists specifically for situations like a dead 12V battery, since it lets you unlock the driver's door manually if the fob's remote unlock function has no power to reach. It is not, by itself, how you start the engine on most vehicles, since push-button cars generally do not have a traditional ignition cylinder for the blade to turn. Its role is opening the car when the doors will not respond to the fob, which matters if your 12V battery is also flat and the power locks will not budge. Check your fob's edges and the small logo panel on its face for a release button or sliding catch; the exact design differs by manufacturer, and the manual will confirm yours.
The fob-against-the-start-button backup method
If the 12V battery is fine but the fob's own coin cell is dead, most keyless vehicles have a documented workaround: hold the fob directly against the start button, with your foot on the brake, and press the button as normal. The button typically contains a low-power reader that can sense the fob's chip at very close range even without the fob's battery, which is enough to authorize the start. Some manufacturers instead provide a dedicated slot near the dashboard, console, or glove box for this purpose rather than the button itself. Because this detail is genuinely different across manufacturers, and some vehicles use neither method exactly as described, your owner's manual is again the correct source to confirm the exact procedure for your car. Once the car is running on a dead fob battery, plan to replace the fob's coin cell before it strands you the same way again.
FAQ
Can you jump start a push-button start car the same way as a regular car?
Yes, if the problem is a flat 12V battery. The clamp connections and jump procedure are the same as any other vehicle; keyless entry only changes how you authorize the start afterward, by pressing the button with the fob present.
What if the dashboard lights are on but the car still won't start?
That pattern usually points to a fob issue rather than a dead 12V battery, since a truly flat battery leaves the whole car unresponsive. Try a spare fob if you have one, or the fob-against-button method described in your owner's manual.
Where are the jump start terminals on a keyless car?
It depends entirely on the make and model. Many modern vehicles route the battery out of the engine bay and provide a separate remote jump terminal instead, but its exact location varies too much to state generally. Your owner's manual is the correct source.
Can a dead key fob battery drain the car's 12V battery too?
Not by design. The two batteries are unrelated, a coin cell inside the fob versus the car's main 12V battery. If both problems appear at once, treat them as a coincidence to check separately rather than assuming one caused the other.
Do I need the fob physically inside the car to jump start it?
Yes. Even once the 12V battery has power restored by the jump, the car still needs to detect a valid fob nearby to authorize pressing the start button, so bring the fob with you.
What if my car has no fob-against-button trick and no accessible key slot?
Procedures genuinely differ by manufacturer, and a small number of vehicles handle this differently than described here. If your owner's manual does not cover it clearly, contact the manufacturer or a dealer for the documented method for your specific model.
How do I know for certain if it's the fob battery and not the 12V battery?
Check whether the dashboard lights, interior lights, and power locks respond normally. If they do and only the start button fails to recognize the fob, it points to the fob's coin cell. If nothing in the car responds at all, it points to the 12V battery.