Start the Car With a Dead Key Fob Battery

Last updated: June 10, 2026

The Toyota C-HR (Mk2, 2023–Present) is a full-hybrid and plug-in-hybrid crossover sold with Smart Entry and push-button start across the range. Its keyless system is more sophisticated than the first C-HR — many cars add a digital key and welcome lighting — but the underlying fallback for a dead fob is the same proven Toyota method. Here is how to get the new C-HR open and started when the coin cell quits.

Start the New C-HR With a Dead Fob

When the fob battery dies the hands-free radio link drops and the dash shows a key-related warning, but the immobiliser can still read the fob’s chip at point-blank range.

1. Get inside (mechanical-key steps below) and settle into the driver’s seat with the door closed.
2. Press the brake pedal firmly and keep it down.
3. Touch the fob flat against the START/STOP button, badge face to the button. Listen for the confirmation beep.
4. With the brake still pressed, push START. The hybrid system powers up to READY and the car is ready to drive.

Because the Mk2 is a hybrid, you may not hear an engine crank — the green READY light and dash coming fully alive confirm it has started. If nothing happens, reposition the fob and try the opposite face.

Unlock With the Hidden Mechanical Key

The door buttons are dead with a flat fob, so use the emergency blade inside the Smart Key.

1. Press the catch on the fob and slide the metal key out.
2. On the Mk2 C-HR the driver’s door lock cylinder is hidden under a slim cover at the rear of the handle. Ease the cover off with the blade tip to reveal the keyhole.
3. Insert and turn to unlock. The alarm may sound until you start the car.

Why Touching the Fob to the Button Works

An induction antenna behind the start button energises the passive transponder in the key — a chip that carries no battery and is woken by the antenna’s field. A flat coin cell only disables the longer-range radio for hands-free locking and detection; the close-range immobiliser handshake still completes. That is precisely the backup Toyota engineers into every Smart Key vehicle, including this latest C-HR.

Replace the Coin Cell

Swap the battery promptly so the digital convenience features come back too.

1. Slide out the mechanical key to expose the case seam.
2. Twist a coin in the slot to part the two halves of the fob.
3. The Mk2 C-HR fob uses a CR2032 3V lithium coin cell. Fit the replacement with the positive (+) side facing the way the old one sat.
4. Hold the new cell by its rim, then click the case shut.

Stand beside the car and press lock once; the buttons and hands-free detection should be back to normal.

Frequently Asked Questions

How do I know my hybrid C-HR has started if there’s no engine noise? Look for the green READY indicator and a fully-lit instrument display after pressing START. In EV/hybrid mode the petrol engine may stay off at idle — that is normal.

Does the digital key still work with a dead fob? The phone-based digital key is separate, but it relies on your phone’s battery and Bluetooth, not the fob’s coin cell. If the physical fob is dead, the touch-to-button method is the reliable fallback.

Where is the keyhole on the Mk2 door handle? Hidden behind a removable cap at the rear edge of the driver’s door handle. The other handles have no barrel.

A key warning stayed on after I fitted a new battery. On hybrids this can also signal a weak 12V auxiliary battery. If a fresh coin cell doesn’t restore keyless entry, have the 12V tested.

Can the metal key start the car? No — it only unlocks the driver’s door. Starting is always through the push button.

If a dashboard warning persisted after you got moving, our sister site autodtcs.com can tell you what the stored code means before you assume it’s the smart-key system.