How to Replace a Subaru Key Fob Battery?

To replace a Subaru key fob battery, work out which of the three Subaru fob styles you are holding, buy the coin cell that matches it, twist the case open with a small flathead screwdriver, and fit the new cell the same way up as the old one. Push-button start fobs take a CR2032. The job takes about three minutes and no reprogramming is needed afterwards.

The one thing that trips people up is buying the battery before checking the fob. Subaru has used three different coin cells across its range, and two Subarus of the same model year can take different ones depending on how the car was equipped. So start here.

First, work out which Subaru fob you have

Look at your fob, not your model year. The shape tells you the battery.

Your fob	Coin cell	How it opens
Rectangular smart key, push-button start, metal blade hidden inside	CR2032	Pull the blade out, twist a screwdriver in the slot it leaves behind
Metal blade sticking out of a plastic head with buttons on it	CR1620	Twist into the notch on the seam, then open a second case inside
Small remote on the keyring with no blade at all	CR2025	Twist into the seam along the edge

The rectangular smart key is what came with most Subarus sold from around 2015 onwards, including the Outback, Forester, Crosstrek, Impreza, Legacy, Ascent, WRX, and BRZ. If your car unlocks when you walk up to it and starts with a button, this is you, and you want a CR2032.

The head key is the one with a metal blade permanently attached to a plastic head. It was common through the 2010s and it hides a CR1620, which is a much smaller and thinner cell than the other two.

This is why the model year on its own will not answer the question. Through the 2010s Subaru fitted the head key to base trims and the proximity smart key to higher ones, so a Forester and its neighbour on the same forecourt could leave with different fobs and different batteries. Checking the fob in your hand takes five seconds and saves a second trip to the shop.

Whichever you have, the number stamped on the flat face of the old battery settles it. If you can open the fob before you go shopping, do that first. Your car’s manual lists the size too, and every Subaru manual is free to download from Subaru’s vehicle resources hub.

What you need

• The right coin cell: CR2032, CR1620, or CR2025
• A small flathead screwdriver, or the metal blade from the fob itself
• A strip of tape or a soft cloth wrapped round the screwdriver tip
• A clear worktop, because a CR1620 that hits a carpet is gone

Buy a name brand cell, and buy it somewhere with turnover. Coin cells lose charge sitting on a shelf, so one that has been in a rack for years starts out weaker than a fresh one.

How to replace the battery

The rectangular smart key (CR2032)

1. Release the metal blade. Turn the fob over and find the small silver tab. Slide it across and hold it while you pull the metal emergency key out. Set the key aside. This matters for more than storage: pulling the blade is what exposes the opening slot.
2. Twist the case open. Inside the empty blade channel there is a narrow slot. Wrap your screwdriver tip so it does not mark the plastic, push it into the slot, and twist. Twist, do not lever. The two halves separate at one clip first, then you work gently round the seam and let the others let go one at a time.
3. Photograph the battery before you move it. Ten seconds on your phone removes all doubt later. On the Subaru smart key the plus face points up at you once the back is off. Lift the old cell out sideways from under the retaining clip rather than levering it straight up, which bends the contact.
4. Fit the new CR2032. Hold it by the rim. Fingerprints on the flat faces sit between the metal and the contact and shorten the life of the cell. Slide it in the same way up as the old one and press until it sits flat.
5. Snap it shut and put the blade back. Line the halves up, press round the whole edge until the clips click, then slide the emergency key home. Run a finger along the seam. Any step you can feel means a clip has not caught.
6. Test it properly. Stand back from the car and press lock, then unlock. Walk up to the door with the fob in your pocket and see whether it recognises you. Then get in, press the brake, and start the engine. Locking, proximity sensing, and starting all use the fob differently, so check all three before you put the screwdriver away.

The head key with the metal blade (CR1620)

This one catches people out, because there is a second case inside the first.

1. Find the notch on the seam. Look along the edge of the plastic head for a small indentation. Push a wrapped screwdriver in and twist to split the outer shell.
2. Lift out the inner unit. Inside the shell you will find a smaller sealed module, not a bare battery. This is normal. Nothing has gone wrong.
3. Open the inner unit. Small tabs run round its seam. Press them and the module opens to reveal the CR1620.
4. Swap the cell, then close both cases. Fit the new CR1620 the same way up, click the inner module shut, drop it back into the shell in the same orientation, and press the shell together.

If the fob is dead the moment you close it, the cell is almost certainly upside down. Open it and turn the battery over before you try anything else. That is the single most common reason a fresh battery changes nothing.

Does the fob need reprogramming afterwards?

No. Your Subaru and its fob keep their pairing in memory that survives a total loss of power, so taking the battery out does not wipe it. Fit the new cell and everything works as it did.

Programming is a different job, and it only comes up when a new fob is being added to the car. On recent Subarus that needs dealer equipment. A battery is a few dollars and a replacement fob with programming runs into the hundreds, so try the cheap fix first.

If the fob still will not work

Go through these in order. The first two explain almost every case:

• Polarity. Open it and flip the cell over.
• Seating. Check the battery is flat under its clip and the case has fully clicked shut. A case that is a millimetre proud will not hold the contact.
• The battery. Cheap cells sometimes arrive flat, and an off spec one can sit a fraction too low. Try a fresh name brand cell.
• Dirty contacts. Wipe the metal clip and both faces of the battery with a dry cloth.
• The inner module, on a head key. Check it went back into the outer shell the same way round it came out. Upside down, the case will close but the contacts will not line up.
• Your spare fob. If the spare behaves perfectly, the fault is inside the first fob, not in the car.

One clue worth knowing. If the buttons do nothing but the car still starts when you hold the fob against the start button, the security chip in the fob is fine and only its radio has failed. That points at the fob, not at the vehicle.

Getting in and starting your Subaru with a dead fob

You are not stranded, but there is one surprise to prepare for.

Slide the silver tab, pull out the metal blade, and use it in the driver’s door lock. On many Subarus that lock sits under a small cover on the door handle that pops off with a fingernail.

Expect the horn. Opening the driver’s door with the blade while the alarm is armed sets the alarm off, because the car never saw the fob unlock it. This is normal Subaru behaviour, not a fault. Pressing any button on a working fob stops it, and so does switching the ignition on. With push-button start, starting the car clears it.

To start the engine, press the brake and hold the fob flat against the START button, then press. There is a coil behind that button that reads the chip inside the fob from a couple of centimetres away, which is why a car with a completely flat fob battery will still recognise the key on contact. Some older models have a fob slot in the dash or console instead, and the fob goes in there.

How long does a Subaru key fob battery last?

Two to three years of daily use, sometimes four in a car that is driven less. The fob tends to warn you first. Range drops, so you find yourself walking closer to the car. One press stops being enough. Newer models put a low key battery message on the dash, and a car that cannot find the fob at all will say so directly.

Cold weather usually delivers the final blow. A cell that is already low puts out less voltage near freezing, which is why fobs give up on the first hard frost rather than in July. If yours is getting vague in the autumn, change it then.

One habit drains the cell faster than anything else. A smart key parked within a few feet of the car, on a hook by the garage door for instance, keeps talking to the vehicle all night. Move the hook further inside and the battery lasts noticeably longer.

What to do with the old cell

Do not put it down on a table or a low shelf. More than 3,500 people in the United States swallow button batteries every year, and one stuck in the throat can cause severe burns in as little as two hours. The 20 mm lithium coin cell, which is exactly what a CR2032 is, is the size most often involved.

Poison Control’s button battery page is worth reading if you have small children in the house. Tape over both faces of the old cell and put it in a battery recycling box. If you think a child has swallowed one, go straight to an emergency room and call the National Battery Ingestion Hotline on 800-498-8666 on the way.

Conclusion

Identify the fob first, because Subaru uses three coin cells and the shape of the fob tells you which. Push-button smart keys take a CR2032, head keys take a CR1620, and older blade free remotes take a CR2025. Pull the blade, twist the case open, note which way the old cell sits, fit the new one the same way, and click it shut. Nothing needs reprogramming.

Frequently asked questions

What battery does a Subaru key fob take?

It depends on the fob, not the model. Rectangular push-button start smart keys take a CR2032, keys with a metal blade in a plastic head take a CR1620, and small blade free remotes usually take a CR2025. The number is printed on the old cell.

Do I need to reprogram my Subaru key fob after changing the battery?

No. The pairing between fob and car survives losing power, so a battery swap changes nothing. Programming only applies when a new fob is added to the vehicle, and on recent Subarus that needs dealer equipment.

Why does my alarm go off when I unlock the door with the metal key?

Because the car never saw the fob unlock it, so it treats the opening as a break in. It is normal. Press a button on a working fob, switch the ignition on, or start the car with push-button start, and the horn stops.

Can I use a CR2032 in place of a CR1620?

No. A CR1620 is 16 mm across and 2 mm thick, while a CR2032 is 20 mm across and 3.2 mm thick. It will not physically fit the holder, and forcing it damages the contacts. Match the number on the old cell exactly.

Why is my Subaru fob still dead after a new battery?

Nine times out of ten it went in upside down, so open it and flip it. If not that, check the cell is flat under its clip, the case is fully shut, and the contacts are clean. Then test your spare fob to see whether the fault is in the fob or the car.

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