Start the Car With a Dead Key Fob Battery

Last updated: June 12, 2026

A dead fob battery will not leave you stuck in the Infiniti QX30 (H15, 2016–2019). The QX30 is the crossover sibling of the Q30 and shares the same Mercedes-derived keyless system, so the fix is an emergency key slot beside the steering column rather than the “hold the fob to the button” method used on Nissan-platform Infinitis. Below are the start procedure, how to unlock with the hidden blade, and how to fit a fresh coin cell.

Start the QX30 with a dead fob battery

An emergency ignition slot sits on the lower left of the steering column. Sliding the fob in lets the slot’s antenna read the transponder directly, so a flat coin cell does not prevent starting.

1. Sit in the driver’s seat with the doors closed and press the brake pedal fully.
2. Find the key slot to the left of the steering column; a small light usually glows beside it when the fob cannot be detected.
3. Insert the Intelligent Key into the slot, orienting the buttons as the port requires (buttons up for a horizontal slot, toward the door for a vertical slot).
4. With the brake held down, press the START/STOP button. The engine fires.
5. Keep the QX30 running until a new battery is fitted — a later restart may not be recognised.

Unlock the doors with the mechanical key

With a flat fob the remote buttons and keyless walk-up entry are disabled, so open the car with the emergency blade.

1. Press the release catch on the back of the fob and slide the metal blade free.
2. Insert the blade into the driver’s door lock and turn to unlock.
3. Open the door. The alarm may chirp briefly until the key is recognised inside.

Immobiliser note

The QX30 immobiliser is paired to a passive transponder inside the Intelligent Key. Because the steering-column slot powers that chip directly, an authorised key still starts the engine with a completely dead coin cell. A flat battery only disables remote locking and proximity detection — the immobiliser is not what stops you.

Replace the key-fob battery

The QX30 Intelligent Key takes a single CR2025 3 V lithium coin cell — the thinner Mercedes-platform cell, not the CR2032 used by Nissan-based Infinitis. Confirm the type printed on the old battery before buying.

1. Slide the mechanical blade out first to release the case latch.
2. Insert a small flat-blade screwdriver into one of the two seam slots and twist to part the halves.
3. Lift out the old cell and fit the new CR2025 positive-side down, close the case, reinsert the blade, and test the buttons.

Frequently Asked Questions

Why won’t my QX30 detect the key? A flat fob battery is the usual cause. Insert the fob into the steering-column slot to start, then replace the CR2025.

Can I hold the QX30 fob against the START button instead? No. The QX30 uses the Mercedes-style emergency key slot, so the touch-to-button trick from Nissan-platform Infinitis does not apply here.

What battery does the QX30 fob use? A CR2025 3 V lithium coin cell, widely available and inexpensive.

Will driving with a dead fob cause damage? No. Only remote locking and walk-up entry stop. The passive immobiliser transponder keeps working.

The car started but a key warning stays lit — normal? Yes. It stays on until a fresh cell is fitted, then clears at the next start.

If a key-detection problem appears together with a dashboard warning light or a stored fault code, our sister site autodtcs.com explains what each OBD-II trouble code means.