🔧 GS - 12V Battery Replacement

Your GS uses a 12-volt battery in the trunk. Replacing it is mostly about safe disconnect/reconnect order, keeping the vent tube connected, and securing the battery so it can’t move.

Difficulty Level: Beginner | Estimated Time: 0.5-1.0 hours

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⚠️ Safety & Precautions

• ⚠️ Turn the car OFF and keep the key fob 10+ feet away so the system stays asleep.
• ⚠️ Remove the negative cable first and install it last to reduce short-circuit risk.
• ⚠️ Do not let a tool touch the positive terminal and body metal at the same time.
• ⚠️ Batteries can vent gas—no sparks, flames, or smoking nearby.
• ⚠️ Keep the battery upright; acid leaks can damage the trunk area.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 3/8" drive ratchet
• 6" extension for 3/8" ratchet
• 12mm socket
• Trim clip removal tool
• Torque wrench (5-30 Nm range)
• Battery terminal puller (specialty)
• Memory saver (OBD-II) (specialty)
• Battery carrying strap
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• 12V car battery (AGM-type if originally equipped) - Qty: 1
• Battery terminal anti-corrosion spray - Qty: 1
• Battery terminal felt washers - Qty: 2

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📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Open the trunk and leave it open (so you don’t get locked out if power is lost).
• If you want to keep radio presets/settings, connect a memory saver (a small backup power device that plugs into the OBD-II port) before disconnecting the battery.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Access the battery in the trunk

• Open the trunk and lift/remove the right-side trunk floor/side cover to access the battery area.
• Use a trim clip removal tool to pop any plastic retainers without breaking them.

Step 2: Disconnect the negative (-) terminal

• Use a 10mm socket with a 3/8" ratchet to loosen the negative terminal clamp nut.
• Wiggle the clamp off the battery post. If it’s stuck, use a battery terminal puller (specialty). Don’t pry on the battery case.
• Tuck the negative cable end aside so it cannot spring back and touch the terminal.
• When reinstalling later: Torque to 5 Nm (44 in-lbs)

Step 3: Disconnect the positive (+) terminal

• Flip open/remove the red protective cover on the positive terminal.
• Use a 10mm socket with a 3/8" ratchet to loosen the positive terminal clamp nut and remove the clamp from the post.
• Move the cable aside so it can’t touch metal.
• When reinstalling later: Torque to 5 Nm (44 in-lbs)

Step 4: Disconnect the battery vent tube

• Locate the small hose on the side of the battery and pull it straight off by hand.
• This is the vent tube (it routes battery gases outside the trunk). Do not leave it disconnected during reassembly.

Step 5: Remove the battery hold-down bracket

• Use a 12mm socket with a 3/8" ratchet and 6" extension to remove the hold-down fastener(s).
• Remove the bracket and set it aside.
• When reinstalling later: Torque to 20 Nm (15 ft-lbs)

Step 6: Remove the old battery

• Put on nitrile gloves and safety glasses.
• Use a battery carrying strap and lift the battery straight up and out (it’s heavy).
• Keep it upright and place it on cardboard or a tray.

Step 7: Install the new battery

• Place the new battery into the tray in the same orientation as the old one.
• Reinstall the hold-down bracket using the 12mm socket, then tighten with a torque wrench: Torque to 20 Nm (15 ft-lbs)
• Reconnect the vent tube by pushing it fully onto the battery vent port.

Step 8: Reconnect terminals (positive first, negative last)

• Install felt washers (if used) on the posts, then apply battery terminal anti-corrosion spray.
• Reconnect the positive (+) clamp first using a 10mm socket, then tighten with a torque wrench: Torque to 5 Nm (44 in-lbs)
• Reinstall the red positive cover.
• Reconnect the negative (-) clamp last using a 10mm socket, then tighten with a torque wrench: Torque to 5 Nm (44 in-lbs)

Step 9: Reinstall trunk trim

• Reinstall the trunk side cover/floor panels.
• Use the trim clip removal tool to align and press clips back into place.

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✅ After Repair

• Start the car and confirm it cranks normally and no warning lights remain on after a short drive.
• Reset the clock and radio presets if they were lost.
• Re-initialize auto-up/down windows if needed: with the car ON, fully lower the window, then fully raise it and hold the switch up for ~2 seconds.
• Check that the trunk area has no battery smell and the vent tube is connected.

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💰 DIY vs Shop Cost

Shop Cost: $250-$450 (parts + labor)

DIY Cost: $180-$320 (parts only)

You Save: $70-$130 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.5-1.0 hours.

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🎯 Ready to get started?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.