Start the Car With a Dead Key Fob Battery

The DS 3 Crossback (2019–Present) — DS Automobiles’ compact crossover, also sold as the DS 3 E-Tense electric — comes with keyless entry and start on most trims. When the fob coin cell dies, the doors stop responding and the START/STOP button shows “key not detected”. It looks like a flat car battery, but it is only the fob. The DS 3 Crossback key still holds a battery-free transponder the car reads at close range, so you can unlock and start it.

Note this is the keyless DS 3 Crossback, not the older DS 3 hatch, which uses a different remote. Get into the car with the blade, hold the fob to the steering column, and the immobiliser reads the chip anyway.

Start the keyless DS 3 Crossback with a dead fob

1. Open the car with the emergency blade (next section), sit in the driver’s seat and close the door so the cabin antenna can search for the key.
2. Press and hold the brake pedal — on the electric E-Tense the same brake-and-button sequence applies.
3. Press the START/STOP button once. The DS cluster shows “key not detected”.
4. Hold the flat face of the fob against the steering column, just left of the START button, over the backup antenna.
5. With the fob held there and the brake pressed, press START/STOP again. The immobiliser reads the passive chip and the car starts, or shows READY on the E-Tense.

Unlock the doors with the emergency key blade

1. Slide the catch on the fob and pull out the metal emergency blade.
2. The DS 3 Crossback has flush, retracting door handles; on the driver’s handle, lever off the small cover at the rear end with the blade tip to reach the hidden lock cylinder.
3. Insert the blade, turn to unlock, then refit the cover. The alarm may sound until the car recognises the key and starts.

Why this works — the immobiliser note

The DS 3 Crossback fob carries a battery-powered radio for hands-free entry and a passive RFID transponder powered wirelessly by the car. A flat coin cell silences only the radio; the transponder still answers the immobiliser when held against the column antenna. That is the whole reason the close-range start works on a dead battery.

Replace the fob battery

The DS 3 Crossback fob uses a single CR2032 3V lithium coin cell — the larger modern cell, not the CR1620 of the old DS 3 hatch, so check the marking. Remove the emergency blade, prise the back cover off where the DS logo sits, lift the old cell and fit the new one with the + face up, then clip it shut. A fresh CR2032 lasts two to three years; once keyless range drops, change it before it strands you.

Frequently Asked Questions

Does the electric DS 3 E-Tense use the same method? Yes. Hold the fob against the steering column and press START/STOP with the brake down to bring it to READY.

Where do I hold the fob on the DS 3 Crossback? Flat against the left of the steering column by the START button. If it doesn’t read first time, nudge the fob a centimetre and press again.

How do I reach the keyhole with the flush handles? Use the blade tip to pop the small cover off the rear of the driver’s door handle, which exposes the lock cylinder.

What battery does the DS 3 Crossback fob take? A CR2032 lithium coin cell — not the CR1620 used by the earlier DS 3 hatch. Match the printed code.

The alarm sounded when I used the blade — is that a fault? No. Mechanical entry trips the alarm by design and it stops as soon as the car reads the key and starts.

If a warning light or fault code appeared with the key message, you can decode it on our sister site autodtcs.com.