Start the Car With a Dead Key Fob Battery

Last updated: June 12, 2026

The Subaru Forester (Mk5/SK, 2019–Present) uses Subaru’s Keyless Access with push-button start, and the START/STOP button itself doubles as a back-up reader for a flat fob. When the coin cell dies, hold the access key fob against the button and the immobiliser still reads the chip, so the SK Forester starts normally.

Start the SK Forester with a dead fob

1. Unlock and get in using the emergency key first (next section), then sit in the driver’s seat and shut the door.
2. Press and hold the brake pedal — the Forester will not start unless the brake is down.
3. Touch the Subaru badge side of the access key fob directly against the push-button START/STOP switch and hold it there. The button contains the back-up reader coil.
4. With the fob still held against the button, press the button. The chip is energised at close range and the engine starts.

If the combination meter shows the key is not detected, press the fob flat and square against the button and try once more — the read range is only a centimetre or so.

Unlock the SK Forester with the emergency key

1. Slide the small release catch on the back of the access key fob and pull out the metal emergency key.
2. At the driver’s door handle, insert the key into the lock cylinder — on the SK it sits behind a slim cover that you pop off the underside of the handle.
3. Turn the key to unlock. The alarm may chirp until the engine is started and the system reads the chip.

Immobiliser note

The fob’s CR2032 cell powers only the proximity broadcast and the lock buttons. Engine authorisation comes from a passive transponder that draws power inductively from the coil behind the start button, so a flat cell never stops you starting the car — it only stops the hands-free locking and remote.

Replace the fob battery

The SK Forester access key uses one CR2032 3V lithium coin cell in a snap-together case with no screws. Pull the emergency key out first, then prise the two halves apart at the seam left by the key slot. Lift the old cell, fit the new one + side up to match, click the case shut and refit the emergency key. Locking and keyless entry work again at once with no re-coding.

Frequently Asked Questions

Do I hold the fob to the start button or the steering column on the SK Forester?

To the START/STOP button. On the Mk5 Forester the back-up reader is built into the button, so that is where the dead fob must touch — not the column.

My Forester has a PIN/access-code feature — can I use it with a dead fob?

2019-on Foresters with the keypad PIN option let you enter your code at the tailgate to unlock, which is a useful back-up if you cannot get the door open. You still start the engine by holding the fob to the button as above.

The emergency key won’t turn the door lock — now what?

Make sure you have removed the small handle cover and seated the blade fully. If it still will not turn, the door may simply be stiff; once inside, the dead-fob start procedure is unchanged.

Is it the fob battery or the car’s 12V battery?

If the cabin is completely dead and nothing lights up when you open the door, suspect the Forester’s 12V battery, not the coin cell. A flat coin cell only affects the remote and hands-free locking.

How long will a CR2032 last in the SK fob?

Typically two to four years. A “key battery low” message in the combination meter is your cue to swap it before it dies completely.

If a warning light stayed on after the no-start, look it up on autodtcs.com to confirm it was only the fob and not an immobiliser fault code.