How To Replace The Battery In A Subaru Keyless Fob: Step-by-Step Guide

Learn how to replace the battery in your Subaru keyless fob using simple household tools to restore instant remote and proximity keyless entry functions. This guide covers modern rectangular and classic teardrop Subaru transmitters, outlining correct battery sizes, precise opening procedures, and immediate troubleshooting steps to avoid costly dealership programming fees.

Pre-Operation Planning & Subaru Fob Battery Identification

Before attempting to open your Subaru keyless remote, identifying your specific fob design and gathering the correct replacement battery is crucial. Using the incorrect battery size or inserting a cell with the wrong voltage can damage the internal circuit board or prevent the transmitter from communicating with your vehicle's receiver.

Most Subaru models from the mid-2000s onward use one of three keyless remote designs: the modern rectangular smart key (used on push-button start models), the classic teardrop-shaped keyless transmitter (common on turn-key ignition models), or the integrated key-head remote. Each style requires a specific lithium coin-cell battery and a careful opening technique to avoid marring the plastic housing or breaking internal retaining clips.

Required Materials, Tools, and Project Benchmarks

• Replacement Lithium Battery: 1x CR2032 (most modern smart fobs, 2015–present), CR1632 (older smart fobs, 2010–2014), or CR1620 (classic teardrop integrated keys).
• Precision Opening Tools: A small flathead screwdriver or a non-marring plastic spudger tool.
• Surface Protection: A clean microfiber cloth or a strip of electrical tape (to wrap around the metal screwdriver tip to prevent scratching the plastic fob body).
• Cleaning Supplies: Isopropyl alcohol (90% or higher) and a clean cotton swab to clean oxidation off battery contacts (optional but recommended).
• Estimated Cost: $2.00 to $8.00 depending on the battery brand.
• Estimated Time: 5 minutes.
• Prerequisite Knowledge: Understanding how to release the mechanical emergency key from the transmitter housing.

Step-by-Step Instructions for Modern and Classic Subaru Fobs

Subaru keyless transmitters fall into distinct design categories based on vehicle generation and ignition type. Follow the appropriate procedure below for your specific key fob style to guarantee a successful battery swap.

Method A: Replacing the Battery in Modern Subaru Smart Keys (Push-Button Start)

This procedure applies to the sleek, rectangular fobs with silver accents used across the Subaru lineup (Outback, Forester, Crosstrek, WRX, Legacy, Ascent) from roughly 2015 to the present.

Step 1: Release and Extract the Emergency Key

Turn the key fob over to expose its back surface. Locate the small, square silver release button positioned near the top of the casing. Press and hold this button down with your thumb while simultaneously pulling the metal keyring loop outward. The emergency mechanical key blade will slide completely out of the transmitter body. Set this key aside.

Step 2: Locate the Internal Pry Points

Hold the key fob with the emergency key cavity facing upward. Peer inside the slot where the key blade was just removed. You will notice a small, structural plastic partition separating the key slot from the rest of the housing, along with a dedicated rectangular notch designed specifically for prying.

Step 3: Split the Key Fob Housing

Wrap the tip of a small flathead screwdriver in a thin layer of electrical tape or microfiber cloth to safeguard the outer plastic from gouges. Insert the protected flathead tip directly into the rectangular pry notch inside the key slot. Twist the screwdriver gently like a key. Avoid pushing the screwdriver deep inside the remote to prevent striking the green circuit board. The twisting motion will cause the two halves of the key fob body to pop open, releasing the perimeter clips. Work your tool around the seam to separate the front and back covers completely.

Step 4: Remove the Old Lithium Battery

Once open, you will see the green circuit board seated on one side, and the round coin-cell battery sitting in its designated circular retaining compartment on the other side. Note the orientation of the battery before removal. The positive (+) side, denoted by engraved text and a plus symbol, must face upward. Use a non-metallic tool, such as a plastic spudger or a wooden toothpick, to gently pry the battery out from under the tiny plastic retention tabs.

Warning: Do not use a metal screwdriver to pry the battery directly out of its seat unless absolutely necessary. Metal tools can bridge the positive and negative contacts inside the holder, short-circuiting the remaining power or permanently damaging the delicate metal battery contacts on the board.

Step 5: Install the New CR2032 Battery

Take your new CR2032 lithium battery out of its packaging. Wipe the surface with a dry microfiber cloth to remove any conductive skin oils. Slide the edge of the new battery under the plastic retaining clips, then press down firmly until the battery snaps flat into the compartment. Ensure that the positive (+) side of the battery is facing upward, toward you.

Step 6: Snap the Fob Halves Together

Align the front and back plastic covers of the key fob. Ensure the rubber weatherproofing gasket is seated properly in its track around the perimeter. Squeeze the two halves together firmly starting at the bottom and working toward the top. You will hear a series of audible clicks as the internal plastic fasteners lock back into place. Slide the mechanical emergency key blade back into its slot until it clicks securely. Test the remote button functions near your vehicle.

Method B: Replacing the Battery in Classic Teardrop and Integrated Key Fobs

This procedure applies to older Subaru keyless entry remotes (generally pre-2015 models) and integrated key remotes where the remote buttons are built into the head of the physical ignition key.

Step 1: Remove the Housing Screw (If Equipped)

Examine the back of the key fob or key head. Some integrated key-head transmitters utilize a single small Phillips-head screw near the base of the key blade to secure the casing. If your key has this screw, use a precision size-0 Phillips screwdriver to remove it by turning counterclockwise. Set the screw in a safe place. If your key fob is a teardrop-shaped remote without an integrated metal key, skip directly to Step 2.

Step 2: Pry Open the Outer Shell

Look along the outer edge of the key fob or key head to locate a small molded indentation or slot. Insert a small, flat-bladed tool (like a mini flathead screwdriver or guitar pick) into this slot. Twist the tool slowly to break the seal and separate the two halves of the shell.

Step 3: Extract the Internal Transmitter Module

On many classic and integrated fobs, the electronics and battery are housed inside a secondary, sealed plastic box nested within the outer shell. If this is the case for your key, lift this small rectangular transmitter block out of the outer key plastic. Use your fingernails or a small pry tool to separate the clips holding this inner module together, exposing the green circuit board and the battery.

Step 4: Replace the Coin-Cell Battery (CR1632 or CR1620)

Locate the battery, noting its polarity. Gently slide the old battery out of its metal bracket. Clean the metal contact prongs inside the holder with a cotton swab dampened with a small drop of isopropyl alcohol if you spot any dark tarnish or white corrosion. Slide the new battery (typically a CR1632 for older smart keys or a CR1620 for integrated keys) into the bracket with the positive (+) side facing the direction indicated by the engraved markings on the plastic or metal holder.

Step 5: Reassemble the Components

Snap the inner transmitter box shut if your key used one, ensuring the soft rubber button pad aligns with the physical switches on the circuit board. Place the assembly back into the outer plastic key shell. Press the outer halves together until they snap shut along the seam. If you removed a tiny retention screw in Step 1, reinstall it now by turning it clockwise until snug. Do not over-tighten, as this can easily strip the soft plastic threads.

Technical Specifications & Battery Compatibility Matrix

Choosing the correct battery cell chemistry, physical dimensions, and voltage parameters is vital for maintaining the optimal transmitter range and longevity of your Subaru key fob. Refer to the matrix below to ensure you purchase the correct coin cell for your specific model year and key variant.

Pro-Tip: Always choose reputable, name-brand lithium batteries (such as Panasonic, Energizer, or Duracell). Cheap bulk batteries often suffer from inconsistent voltage delivery and high self-discharge rates, leading to premature fob failure in cold weather.

Diagnosing Post-Replacement Failures & Field Remedies

If your Subaru keyless remote fails to operate after installing a fresh battery, use the following structured diagnostic scenarios to pinpoint and resolve the underlying issue.

• Scenario 1: The key fob is completely unresponsive and the small LED indicator on the remote does not illuminate when buttons are pressed.

  
  
  
  • Root Cause: The new battery was installed upside down, preventing circuit completion; the battery has a clear, non-conductive protective film on its underside; or the delicate metal contact prongs inside the fob have lost physical contact with the battery surface.
  • Actionable Fix: Open the key fob housing. Check the back of the battery to verify that any clear plastic safety stickers have been completely removed. Confirm that the positive (+) side of the battery is oriented correctly. Inspect the metal contact prongs inside the holder; if they have been flattened or bent downward, use a plastic toothpick or a fine sewing needle to carefully lift them back up to ensure a firm, spring-loaded connection with the battery.

• Scenario 2: The physical buttons on the keyless remote work, but the vehicle fails to recognize the proximity key for push-button start, displaying a "Key Not Detected" warning on the dashboard.

  
  
  
  • Root Cause: The battery is weak out of the box, or the fob's internal transceiver requires a momentary proximity resync with the vehicle's immobilizer module.
  • Actionable Fix: To start the engine with a weak or desynced key fob, depress the brake pedal and hold the key fob with the Subaru logo facing directly against the vehicle's physical Engine Start/Stop button. The immobilizer system uses passive RFID technology to read the key at close range even if the battery is critically low. To resync the proximity system, drive the vehicle for a brief period or cycle the accessory power several times with the key inside the cabin.

• Scenario 3: The keyless fob buttons feel spongy, catch on the outer plastic casing, or fail to click.

  
  
  
  • Root Cause: Misalignment of the green circuit board or the internal silicone rubber button membrane during reassembly.
  • Actionable Fix: Re-open the key fob shell. Lift the circuit board and the silicone rubber keypad completely out of the plastic housing. Realign the rubber buttons into their respective cutouts first, ensuring they pop through the front of the shell cleanly. Place the circuit board flat against the rubber backing, making sure it sits flush within the aligning plastic tabs. Carefully snap the back cover back on.

• Scenario 4: The keyless fob works only when standing directly next to the driver's door, whereas it previously worked from dozens of yards away.

  
  
  
  • Root Cause: A low-voltage battery cell was installed, or there is local electromagnetic interference (EMI) blocking the radio frequency.
  • Actionable Fix: Measure the voltage of the replacement battery with a digital multimeter; it should register at least 3.0V to 3.3V. If the voltage is correct, check if the issue persists in different geographic locations to rule out interference from high-power radio towers or wireless security systems.

Frequently Asked Questions

Will replacing my Subaru key fob battery reset the remote programming?

No. Your Subaru's keyless transmitter stores its pairing signature in non-volatile flash memory, which does not require constant electrical current to maintain. Changing the battery will not delete this pairing, and the remote will function normally immediately after reassembly.

How do I open the Subaru keyless fob without a flathead screwdriver?

If you do not have a flathead screwdriver handy, you can use the physical emergency key blade that you extracted from the remote. Insert the tip of the key blade into the molded notch inside the key slot and twist it gently to pry the two halves of the casing apart.

Why is there a tiny red light flashing on my Subaru key fob?

The tiny red LED light is a transmission indicator. It flashes when a button is pressed to confirm that the remote is actively sending an RF (Radio Frequency) signal to your vehicle. If this light flashes rapidly on its own or fails to light up when buttons are pressed, it is a clear indicator that the battery is depleted.

Can I use a CR2025 battery in place of a CR2032 in my modern Subaru remote?

No. While both batteries share the same 3.0-volt charge and 20mm diameter, the CR2025 is only 2.5mm thick, whereas the CR2032 is 3.2mm thick. Using a CR2025 in a fob designed for a CR2032 will leave a physical gap inside the compartment, causing the battery to lose connection with the contacts and render the remote unreliable.

Keep Your Subaru Running at Peak Performance

If your keyless entry system requires professional diagnostic troubleshooting or you need a spare OEM transmitter matched to your vehicle's computer, seek out an authorized dealership or certified automotive locksmith. Ensure your vehicle remains safe and reliable on every journey by using high-quality components and trusted diagnostic services.