Do it yourself guide
How to Jump Start a Keyless Car
About 6 minutes to read
A keyless car with a flat battery throws up problems a traditional key never did. The doors may not unlock, the bonnet release is inside a car you cannot open, and pressing the start button does nothing because the car cannot see the fob. None of that means the jump itself is different. It just means there are a few extra steps before you reach the leads.
This guide covers getting in, finding where to connect, and getting the car to recognise the fob once there is power again. If the fob battery is the real culprit rather than the car battery, it also shows you how to tell.
Getting a keyless car started
1Find the mechanical key inside the fob
Almost every keyless fob hides a metal blade. Look for a small slider or button on the fob body. The blade opens the driver door, usually through a lock hidden under a small cover on the handle that you prise off gently with the blade tip.
2Expect the alarm
Opening the door with the blade on a car with no power, or very little, can set the alarm off once power returns. It will stop once the car recognises the fob. Warn the neighbours if it is late.
3Release the bonnet and locate the jump points
Pull the bonnet release in the footwell. On many modern cars the battery lives in the boot or under a seat, with dedicated positive and earth jump points under the bonnet instead. The handbook shows where they are, and they are often marked with a plus sign under a red cap.
4Connect in the normal safe order
Red to the positive jump point, red to the donor positive, black to the donor negative, final black to the marked earth point or bare engine metal. Let the donor or jump pack supply power for a few minutes before trying to start.
5Hold the fob against the start button or backup spot
If the car says no key detected, the fob battery may be weak too. Most keyless cars have a backup: press the start button with the fob itself, or place the fob in a marked slot or on a marked spot in the centre console or steering column. The handbook will show which your car uses.
6Foot on the brake or clutch, then press start
Keyless cars will not crank without the brake pedal on an automatic or the clutch on a manual. Press start once and let the car do the cranking itself. Try in short attempts with a rest between.
7Disconnect and keep the engine running
Remove the leads in reverse order with the engine running. Then drive for a proper length of time rather than switching off at the next shop, because the battery needs real charge back.
Car battery or fob battery?
Both cause a keyless car to refuse to start. These signs help you tell them apart.
| What you see or hear | What it means | What to do |
|---|---|---|
| Doors will not unlock with the fob, dash is dark | Car battery flat | Use the key blade, then jump start |
| Dash lights come on but the car says no key detected | Fob battery weak, car battery may be fine | Use the fob backup spot or slot, then replace the coin cell in the fob |
| Start button lights up, starter clicks or cranks slowly | Car battery low | Jump start, then get the battery tested |
| Everything works with the spare fob | The main fob battery or fob itself is the fault | Replace the fob coin cell. No jump needed |
What catches people out
- Clamping onto the battery negative on a car with a battery sensor instead of the marked earth point, which can upset the charging afterwards.
- Trying to force the door handle cover off with a screwdriver and scratching the paint, when the key blade tip is designed to do it.
- Leaving the fob in a pocket next to a phone or other keys, which can stop the car reading a weak fob.
- Pressing start repeatedly without the brake or clutch pressed, and assuming the jump has failed.
- Forgetting that a keyless car left locked for weeks still draws power as it listens for the fob, which is often why it went flat.
If you would rather we did it
We jumpstart keyless and push button start cars and vans 24 hours a day. We test the battery and charging on site, and if the battery is finished we can supply and fit the correct type there and then, including EFB and AGM batteries for stop start models, with warranty included.
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Questions
Q.Can you jump start a keyless car?
Yes. Electrically it is the same as any other car. The extra steps are getting in with the hidden key blade and getting the car to recognise the fob once it has power.
Q.Where do I connect jump leads on a keyless car?
Use the jump points the manufacturer provides, usually under the bonnet, even if the battery itself is in the boot. The handbook shows their location.
Q.Why does my keyless car say key not detected after a jump?
The fob battery is probably weak. Use the backup spot or slot described in your handbook, then fit a new coin cell in the fob.
Q.Will a jump start reset my keyless system?
Usually not. Some cars need the windows or clock reset afterwards, but the fob normally pairs again as soon as the car has power.
The short version
Open the car with the key blade hidden in the fob, connect to the marked jump points in the usual safe order, then hold the fob to the start button or backup spot with your foot on the brake or clutch. If the car still does not see the key, the fob battery is the next suspect.