How To Change Battery In Subaru Key Fob: Step-by-Step Guide

Replacing the battery in your Subaru key fob requires a CR2032 or CR1632 3-volt lithium coin cell battery, a small flathead screwdriver, and protective electrical tape to prevent plastic marring. By releasing the internal mechanical emergency key and carefully levering the dedicated seam notch, you can safely open the housing, swap the depleted cell, and restore your remote keyless entry without losing vehicle transponder synchronization.

Pre-Maintenance Subaru Fob Equipment & Model Verification Checklist

Before opening your Subaru remote key casing, you must identify your exact fob generation and gather the proper precision tools. Subaru utilizes two distinct key fob architectures across its vehicle lineup, each requiring a specific battery type and disassembling technique.

Applying excessive force or using uninsulated metal tools can snap internal retention tabs, tear moisture-sealing rubber gaskets, or short-circuit the printed circuit board (PCB). Preparing the correct workspace and components ensures a seamless battery replacement without damaging the expensive integrated transponder hardware.

Essential Gear and Replacement Materials

• Target Replacement Battery: One Panasonic, Energizer, or Duracell 3V Lithium Coin Cell (CR2032 for modern smart keys; CR1632 for older integrated head keys).
• Precision Opening Tool: Flathead micro-screwdriver (2.0mm to 3.0mm blade tip width) or a rigid plastic trim prying tool.
• Surface Protection: Vinyl electrical tape or masking tape to wrap around the screwdriver tip to avoid scratching the key casing.
• Cleaning Supplies: Precision microfiber cloth and 99% isopropyl alcohol (optional, for clearing oxidized terminal contacts).

Mandatory Prerequisite Standards and Knowledge

• Model Generation Rules: Subaru vehicles equipped with Push-Button Start (2015–Present Outback, Forester, Crosstrek, Ascent, Impreza, WRX, Legacy) almost universally use the teardrop-style smart key powered by a CR2032 battery. Turn-key ignition models and pre-2015 smart keys typically utilize a CR1632 battery housed inside a rectangular or oval body.
• Static Electricity Safety: Work on a non-conductive, clean surface (such as a wooden desk or silicone mat) to eliminate electrostatic discharge that could damage the sensitive radio frequency (RF) transmitter chip.

Project Benchmarks

• Estimated Budget: $3.00 to $8.00 USD for a two-pack of name-brand lithium batteries.
• Total Duration: 3 to 5 minutes.
• Technical Skill Level: Beginner (DIY friendly, no diagnostic programming required).

Comprehensive Subaru Key Fob Battery Replacement Workflow

Follow this procedure to disassemble the housing, remove the spent battery cell, install the new power supply, and reassemble your Subaru key fob without disrupting the vehicle pairing code.

Step 1: Disengage Emergency Mechanical Key

1. Hold the key fob with the rear facing upward so the silver release button or latch is visible.
2. Depress and hold the small silver spring-loaded release button located on the back or side of the housing.
3. Pull the metal emergency key out from the bottom base of the key fob body. Set the mechanical key aside in a safe spot.

Pro-Tip: The mechanical emergency key provides access to the driver-side door lock cylinder if your vehicle's main battery or key fob battery dies completely. Keep this key free from dirt and lubricant build-up.

Step 2: Protect the Housing Seam and Pry Point

1. Wrap a single layer of vinyl electrical tape around the tip of your 2.0mm or 3.0mm flathead screwdriver. This prevents metal-on-plastic friction, preserving the cosmetic integrity of the fob's seam edges.
2. Inspect the cavity left exposed by the removed mechanical key. You will see a small, rectangular notch or pry-slot designed specifically for housing separation, located along the internal plastic seam.

Warning: Never force the screwdriver blade directly into the outer exterior perimeter seam of the key fob without using the designated interior pry slot. Doing so can shear off plastic locking tabs and prevent the key fob from snapping tightly back together, compromising its water resistance.

Step 3: Separate Key Fob Halves with Controlled Leverage

1. Insert the tape-wrapped screwdriver blade firmly into the internal pry slot.
2. Apply gentle, steady rotational force—twisting the screwdriver like a key—rather than prying or levering up and down.
3. Listen for a distinct popping click as the internal plastic retention clips release.
4. Work the screwdriver along the primary seam to gently separate the front half (containing the rubber buttons) from the back half (containing the battery tray).

Step 4: Access Battery Cavity and Circuit Board

1. Place the opened fob halves on your clean work surface.
2. On 2015+ teardrop smart keys, the green printed circuit board (PCB) may lie loosely inside or be protected by a black plastic inner module. Lift the inner rubber button pad or circuit block out carefully if necessary.
3. Identify the circular coin cell battery housing held in place by metallic spring tension tabs.

Step 5: Depose Depleted Cell and Verify Polarity Orientation

1. Note the orientation of the original battery before removal. On virtually all Subaru key fobs, the positive side marked with a plus sign (+) must face DOWN or UP depending on the specific model layout (modern teardrop smart keys require the + sign facing DOWN toward the back cover, whereas older turn-key fobs have the + sign facing UP). Look for the stamped "+" or "-" indicator on the plastic housing floor.
2. Insert the edge of your micro-screwdriver or a plastic pry stick underneath the battery release notch opposite the metal tension contacts.
3. Pop the depleted lithium battery out of its retaining housing ring.

Warning: Avoid touching the flat top and bottom surfaces of the new lithium battery with bare fingers. Skin oils leave residues that accelerate corrosion and reduce electrical connectivity, cutting battery lifespan by up to 50%. Handle new cells strictly by their insulated rubber edges or wear clean nitrile gloves.

Step 6: Seat New Coin Cell and Reassemble Housing

1. Remove the new CR2032 or CR1632 battery from its protective blister packaging.
2. Wipe the battery surface with a clean, dry microfiber cloth to remove any factory film or dust.
3. Slide the new battery beneath the metal retaining tabs at a shallow 30-degree angle, then push down firmly until it seats flat within the circular recess. Verify that the polarity orientation matches the factory marking (+ facing the correct direction).
4. Realign the circuit board and internal rubber seal if they shifted during battery removal. Ensure the rubber O-ring gasket rests fully inside its channel along the perimeter wall to preserve moisture protection.
5. Align the front and back plastic halves of the key fob casing.
6. Press the two halves together firmly starting from the top loop and moving toward the base. Apply pressure across all edges until you hear consecutive snapping sounds confirming that all locking tabs are securely engaged.

Step 7: Conduct Signal Verification and Proximity Calibration

1. Reinsert the metal emergency mechanical key back into the key fob base until the spring button snaps locked.
2. Stand within 10 feet of your Subaru vehicle and press the Unlock or Lock button.
3. Confirm that the vehicle responds with visual light flashes and an audible horn chirp.
4. Check the small red LED indicator light on the corner of the key fob housing. It should emit a sharp, bright flash upon every button press.
5. For Push-Button Start vehicles, step inside the cabin with the key fob, depress the brake pedal, and press the engine Start button to confirm immediate transponder recognition.

Subaru Key Fob Specifications & Battery Compatibility Matrix

Choosing the correct power cell and understanding hardware variations across model years prevents key housing damage and operational failures. Review the technical parameters below to match your Subaru vehicle with the correct battery configuration.

Resolving Key Fob Post-Battery Replacement Malfunctions

If your Subaru key fob fails to operate or behaves erratically following a battery change, the underlying issue usually relates to contact alignment, reverse polarity installation, or signal interference. Use the diagnostic matrix below to troubleshoot common real-world failures.

Failure Scenario 1: Key Fob Is Completely Non-Responsive (No LED Flash, No Door Lock Action)

• Root Cause 1: The new lithium coin cell battery was installed upside down (reversed polarity orientation), preventing power from reaching the circuit board.
• Actionable Fix: Reopen the key fob housing using the internal seam notch. Inspect the positive (+) symbol on the battery. On modern 2015+ teardrop key fobs, the + side must face DOWN into the back cover shell. Flip the battery over, snap the housing shut, and test.
• Root Cause 2: Fingerprint oil or protective factory sticker film remains on the battery contact points.
• Actionable Fix: Remove the battery. Inspect the cell for clear protective adhesive film (often placed on new CR2032 batteries child-safety packaging). Wipe both sides of the coin cell with 99% isopropyl alcohol and re-seat.

Failure Scenario 2: Red LED Light Flashes on Fob, but Vehicle Fails to Respond or Start

• Root Cause: The vehicle's keyless entry module has lost rolling-code synchronization due to rapid button cycling while the battery was out, or the key fob is stuck in power-saving mode.
• Actionable Fix: Stand beside the driver's door. Hold the Lock and Unlock buttons simultaneously on the key fob for 5 to 7 seconds until the key's red LED blinks twice. Release the buttons, wait 3 seconds, and press Unlock once to re-synchronize the rolling code sequence with your Subaru's Body Integrated Unit (BIU).

Failure Scenario 3: "Key Fob Battery Low" Warning Warning Persists on Dashboard Instrument Cluster

• Root Cause: The new replacement battery's voltage is below the system's threshold (under 2.85 volts), often caused by purchasing old stock batteries, or the vehicle's computer has not completed a power cycle.
• Actionable Fix: Test the replacement cell with a digital multimeter. A fresh 3V lithium coin cell should measure between 3.2V and 3.3V DC unloaded. If the voltage measures below 3.0V, replace it with a fresh name-brand battery. If the voltage is verified good, start the vehicle engine with the key fob present and allow it to run for 60 seconds to clear the cached low-battery diagnostic trouble code.

Failure Scenario 4: Push-Button Start Fails to Detect Key ("Key Not Detected" Warning)

• Root Cause: The active internal radio-frequency transmitter circuit is disrupted, or the metal contact tabs inside the key fob lost tension and are not making connection with the battery.
• Actionable Fix: Reopen the key fob casing and carefully lift the gold-plated metal tension contact tabs upward by 0.5 millimeters using a toothpick to increase pressure against the battery casing. To start the vehicle immediately in an emergency, touch the physical Subaru emblem on the key fob directly against the push-to-start engine button while depressing the brake pedal; an passive RFID chip inside the fob will bypass the dead battery and allow the engine to crank.

Frequently Asked Questions

Does changing my Subaru key fob battery clear its programming?

No, changing the battery will not delete or reset your Subaru key fob's stored programming. The transponder chip's unique security pairing code is stored in non-volatile memory (EEPROM) within the key fob circuit board, which retains all pairing data indefinitely even when completely unpowered.

How do I start my Subaru if the key fob battery dies completely?

You can still start your Subaru with a dead key fob battery. Remove the emergency mechanical key from the fob to manually unlock the driver's side door, sit in the driver's seat, depress the brake pedal, and push the engine Start/Stop button directly with the nose of the key fob (holding the Subaru logo side against the button). The car's induction coil will read the passive RFID chip inside the key and start the engine.

How long does a Subaru key fob battery typically last?

A standard CR2032 or CR1632 battery inside a Subaru key fob lasts between 2 to 3 years under normal usage conditions. Key fobs for vehicles equipped with keyless access and push-button start consume power faster because they continuously emit a low-frequency proximity signal to detect when you approach the vehicle.

Why is my Subaru key fob still not working after putting in a brand-new battery?

If a new battery does not restore function, ensure you removed any clear protective tape stuck to the underside of the new cell and verify the battery is placed with the correct polarity (+ orientation). If the red LED light on the fob illuminates but the car does not react, your car's main 12V 12-volt battery under the hood may be discharged, or the fob requires rolling-code resynchronization.

Ensure Your Subaru Remains Ready for the Road

Routine maintenance on your Subaru components keeps your daily drive seamless and stress-free. Keep a spare set of CR2032 or CR1632 batteries in your glove compartment or home toolbox so you are never caught unprepared by an unexpected smart key failure.