These instructions apply to the Subaru WRX Mk1 (VA) 2015-2021.
For other models, please choose your vehicle here.
When the remote on a Subaru WRX (VA, 2015–2021) starts making you stand right next to the door before it will lock or unlock, the culprit is nearly always the little coin cell inside the fob rather than anything wrong with the car. The VA-generation WRX — the first WRX sold as its own model line rather than a hopped-up Impreza — shipped with two remote styles depending on trim: a keyless-access “smart” fob on Premium and Limited cars (the one that lets you keep the key in your pocket and start with the button), and a simpler remote-entry key on base cars. Both are easy to service at home in a couple of minutes, and this guide walks through the exact cell, how the case comes apart, and why a spare key is the one thing you can’t sort yourself.
How to Tell the Fob Battery Is Dying
- You have to be almost touching the car. Range collapsing from across the car park to arm’s length is the earliest and most reliable warning sign.
- Push-button start gets fussy. On keyless-access cars you may see a “Key battery is low” or key-warning symbol in the combination meter, and the car may ask you to hold the fob against the start button to start.
- The fob no longer flashes. The red LED on the remote should blink on every button press; a cell that’s too weak to transmit often can’t light it either.
- It only plays up when it’s cold. A tired lithium cell loses voltage in low temperatures, so a fob that’s fine in summer can drop out on a frosty morning.
Reckon on two to four years from a fob battery. A keyless fob left right next to the car keeps waking to look for it, so those tend to run flat sooner.
The Battery You Need
Both WRX remote styles take a single CR2032: a 20 mm, 3-volt lithium coin cell that any supermarket, hardware shop or petrol station will stock. Fit a fresh branded cell rather than a bargain multipack — the transmitter pulls a brief burst of current on each press, and a cheap cell can sag under that load and give poor range even straight out of the packet.
Method 1 — Keyless-Access “Smart” Fob
- Slide the release catch on the side of the fob and pull the metal emergency key blade straight out. This is what gives you a purchase point to open the case.
- Slot a flat plastic pry tool (or the emergency blade itself) into the gap the blade left, or into the seam that runs around the fob, and twist gently to pop the two halves apart. It takes very little force.
- Lift out the old CR2032. Fit the new one with the positive (+) face pointing up, toward the back cover of the fob.
- Press the halves together until they click all the way round, then push the emergency blade back in until it latches.
Method 2 — Base Remote-Entry Key
- Look at the back of the fob. If there’s a small screw, undo it with a fine cross-head driver; if not, there’s a seam you can prise apart.
- Ease the case open with a flat plastic tool, working round the edge so the clips release rather than snap.
- Note which way the old cell faces before you touch it, then swap in the new CR2032 the same way round.
- Close the case, refit any screw snugly — the housing is plastic, so don’t crank it — and test every button.
⚠️ Mind the polarity. A CR2032 dropped in upside down bridges the contacts the wrong way, gives you no range, and can slowly drain itself flat while it sits there. The smart fob wants the plus side up; if you’re ever unsure, copy the orientation of the cell you just removed.
Confirm It Worked
Step back a good few metres and lock, then unlock, the car. Full range should be back straight away and the LED should blink cleanly on each press. If the meter had been showing a low-key warning, it clears once the car has read a healthy fob — sometimes instantly, sometimes after the next start.
If a Fresh Cell Doesn’t Fix It
- Re-seat the battery. It has to sit flat and firm under its clip against clean metal; a cell that’s slightly proud makes intermittent contact.
- Clean the terminals. A wipe with a dry cloth clears finger grease or light tarnish that can throttle the signal.
- Rule out the car’s 12 V battery. If the WRX is slow to wake or the dash lights are dim, a weak main battery can mimic key faults.
- Try the spare. If a known-good second fob acts the same way, the receiver is a likelier suspect than either remote — time for a dealer or locksmith to scan it.
New Key or Spare — Why It’s a Dealer Job
Changing the cell leaves the fob’s existing coding untouched, so there’s nothing to reprogram — it works the moment the case clicks shut. Adding a spare or replacing a lost key is a different story: Subaru’s immobiliser has to be married to the new fob with a diagnostic tool, and blank keyless fobs are ordered against the car’s VIN and cut to match. That’s a job for a Subaru dealer or a properly equipped locksmith, so it pays to keep your spare’s battery fresh too — that way you’re never down to a single working key.
Frequently Asked Questions
What battery does a Subaru WRX key fob take?
A single CR2032 3-volt lithium coin cell — the same size whether you have the keyless-access smart fob or the base remote-entry key.
Which way round does the battery go?
On the keyless-access fob the positive (+) side faces up, toward the rear cover. On the base remote, match the orientation of the cell you removed. Getting it backwards leaves the key dead and can flatten the new cell.
Do I have to reprogram the WRX after changing the battery?
No. A battery swap doesn’t affect the fob’s coding, so it pairs with the car again the instant you close the case. Only a brand-new key needs programming.
How long should the fob battery last?
Usually two to four years. A keyless fob stored right beside the car wakes constantly and can run down a little quicker, so don’t be surprised if yours is at the shorter end.
The key still won’t work with a new battery — now what?
Check the polarity and that the cell sits firmly, then wipe the contacts. If the LED still won’t light with a known-good cell, the transmitter itself may have failed, which is rare compared with a flat or upside-down battery.
Can I still start the WRX if the fob is completely dead?
Yes. Use the emergency blade to unlock the driver’s door, then hold the fob against the push-button start (the car reads it by proximity) and press the brake to start. A flat cell won’t leave you stranded.
If the remote died the moment the car’s 12 V battery was disconnected — rather than fading over weeks — the cause is more likely the pairing than the cell, and there may be a stored code behind it worth reading on autodtcs.com.
Independent guide — not affiliated with Subaru. Always follow your official service manual and safety precautions. Read our full disclaimer.