Start the Car With a Dead Key Fob Battery

Last updated: June 12, 2026

The Kia Picanto (Mk3/JA, 2017–Present) is sold across a wide trim ladder, and which starting system you have decides what to do when the remote dies. Base and mid Picantos use a conventional bladed key you slot into the ignition; higher trims with the Smart Key pack get keyless entry and a push-button start. If the fob has gone quiet, the right recovery depends on which of those two your Picanto has.

Start a Push-Button Picanto With a Dead Fob

If your Picanto has a START/STOP button and the dash shows “Key not detected”, the radio in the fob is dead but the immobiliser can still read the key’s passive transponder at point-blank range.

1. Get into the car first using the emergency blade (see below), sit in the driver’s seat and press the brake pedal down hard.
2. Hold the Smart Key flat against the START/STOP button, keeping the fob roughly square to the button so its transponder coil sits over the reader behind it.
3. With the fob still touching, press the button through the fob. The immobiliser energises the chip, recognises your key and releases the engine.
4. The engine cranks and starts. If nothing happens first time, rotate the fob a few degrees and try again — the read zone behind the button is only a centimetre or two wide.

Picantos with the ordinary bladed ignition are simpler still: slide the metal key into the barrel and twist as you always do — a flat coin cell never stops a turn-key Picanto starting.

Unlock the Door With the Emergency Key Blade

A dead fob will not pop the locks by radio, so Kia folds a metal blade into the key.

1. On a Smart Key, press the small release catch on the back and pull the metal blade straight out. On a standard fob the blade releases from a chrome button on the side.
2. Go to the driver’s door. If a slim cap covers the lock cylinder behind the handle, lever it off with the blade tip to expose the barrel.
3. Insert the blade and turn to unlock. The alarm may chirp; starting the car clears it.

Why a Flat Battery Doesn’t Lock You Out

The Picanto’s immobiliser never depended on the coin cell to verify your key. Inside the fob is a passive transponder powered by induction from the car’s reader coil, like a contactless bank card. The dead battery only kills the long-range radio that locks the doors from a distance. Hold the fob against the button, or twist the blade in the ignition, and the short-range coil powers the chip directly so the car still knows the key is yours.

Replace the Coin Cell

1. Pull the emergency blade out to expose the seam in the fob.
2. Twist the two halves apart with a coin or thin plastic tool, working from the slot the blade left.
3. The Mk3 Picanto fob uses a single CR2032 3V lithium coin cell. Note which way up the old one sits — the plus (+) side usually faces the rear cover.
4. Fit the new cell the same way, handling it by the edges so finger oils don’t shorten its life, then clip the halves together until they click.

The buttons should respond again at once. A fresh cell lasts roughly two to three years.

Frequently Asked Questions

Where exactly do I hold the fob on a push-button Picanto? Flat against the START/STOP button on the dash, ideally square to it. That is where the backup reader coil sits — there is no slot or cubby to drop the fob into on the Mk3.

My Picanto has a normal turn key. Does the dead battery stop it starting? No. The flat battery only affects the remote-lock buttons. Use the blade in the door to get in and the same blade in the ignition to start.

Where is the hidden door lock? Behind the driver’s door handle, often under a small clip-off cap. Prise the cap off with the blade to reach the barrel.

Which battery does the Mk3 Picanto fob take? A CR2032, sold in any supermarket or hardware shop.

The car only started when I touched the fob to the button — is something broken? Usually it just means the coin cell is weak or flat. Fit a fresh CR2032; if it keeps happening with a new cell the fob’s transmitter may be failing.

If a warning light stayed on after you got moving, you can look up exactly what the code means on our sister site autodtcs.com.