How to Replace the Auxiliary Battery on a 2025 Toyota Tundra (V35A-FTS)

If your 2025 Toyota Tundra is showing signs of electrical issues—like slow starts, dim lights, or warning messages on the dash—it may be time to replace the auxiliary battery. This battery supports key vehicle systems and ensures reliable starts, especially on Tundra Hybrid (HV) models. Replacing it with a genuine Toyota OEM auxiliary battery keeps your truck performing at its best.

In this guide, we’ll explain what the auxiliary battery does, when it’s time to replace it, and how to perform a safe, step-by-step removal and installation.

Why the Auxiliary Battery Matters

The auxiliary battery is separate from your Tundra’s main hybrid or starting battery. It powers essential electronics such as:

• Control modules and sensors

• Lighting and accessories

• Key-off memory (clock, radio presets, etc.)

A failing auxiliary battery can lead to unreliable starts or loss of key vehicle settings. Using a genuine Toyota replacement battery ensures perfect fitment and the correct specifications for the V35A-FTS 3.5L twin-turbo V6 engine.

Signs Your Tundra’s Auxiliary Battery Needs Replacement

• Slow cranking or trouble starting

• Dimming interior or exterior lights

• Warning lights on the dashboard

• Measured voltage consistently below manufacturer specs

If you notice any of these issues, it’s time to plan a replacement before the battery leaves you stranded.

Tools and OEM Parts You’ll Need

Before starting, gather the right parts and tools. Using Toyota OEM components ensures long-term reliability and factory-correct fitment.

• Genuine Toyota Auxiliary Battery (V35A-FTS specification)

• Battery terminal wrench

• Protective gloves and safety glasses

Shop all Toyota Tundra OEM batteries and accessories

to ensure your replacement meets Toyota’s quality standards.

Step-by-Step: How to Remove the Auxiliary Battery

Toyota’s official service information outlines a clear removal process

Auxiliary Battery (V35A-FTS) - …

. Below is a simplified summary:

1. Precaution and Safety

   • Switch the ignition OFF and remove the key.

   • Disconnect the negative terminal first to prevent short circuits.

2. Remove Interior Components

   • Remove the rear seat cushion assembly (LH) to access the auxiliary battery compartment.

3. Disconnect Battery Components

   • Remove the battery cover.

   • Detach the negative and then the positive auxiliary battery terminals.

   • Disconnect the battery hose.

4. Remove the Battery Clamp and Battery

   • Unbolt the No. 3 battery clamp.

   • Carefully lift out the auxiliary battery.

Pro Tip: Always handle the battery carefully to avoid spilling electrolyte or damaging surrounding components.

Reinstallation and System Reset

After installing the new auxiliary battery, some electronic systems may require calibration or initialization. This can include window auto-up/down, steering angle sensors, or other key vehicle settings. Follow Toyota’s service instructions or have a certified technician perform these resets for you

Auxiliary Battery (V35A-FTS) - …

.

Order Genuine Toyota Tundra Parts Online

When replacing critical electrical components like the auxiliary battery, OEM parts are essential. Aftermarket batteries may not match Toyota’s exact specifications, which can shorten lifespan or cause electrical issues.

Shop confidently for 2025 Toyota Tundra OEM auxiliary batteries

and related accessories from our parts store. We ship fast and guarantee every part is Toyota-approved for a perfect fit.

Keep Your Tundra Ready for the Road

Your Toyota Tundra was built for reliability and performance. Keeping the auxiliary battery in top shape is a small step that makes a big difference. Whether you drive the hybrid or gasoline model, replacing your battery with a genuine Toyota part ensures the truck you depend on starts every time.

Shop OEM Batteries and Accessories Today
Upgrade and protect your Tundra with genuine Toyota parts engineered for your exact model year. Browse our full selection of OEM batteries, clamps, and accessories

and keep your truck running strong.

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