Alpine 4 Channel Amplifier and Powered Subwoofer Installation Guide | 2016-2023 Tacoma

🛠️ Please read this entire guide before beginning your installation:

Your kit now includes the updated Alpine KTA-450 amplifier, which is different from the amplifier shown in the installation video below.

The installation video can still be used as a general guide. However, some amplifier connections, settings, and installation steps have changed with the KTA-450.

Please follow the written instructions in this guide whenever they differ from the video.

If you have any questions during your installation, please contact our support team at support@trailgridpro.com.

Welcome to the installation guide for your 2016–2023 Toyota Tacoma Alpine Plug & Play 4-Channel Amp & Powered Subwoofer Kit from Trail Grid Pro! This step-by-step guide is designed to make the installation process as smooth as possible, whether you're a seasoned DIYer or tackling your first head unit upgrade.

In this guide, you’ll find:

• 📢 Important Updates: The written guide includes the latest updates and adjustments that may not be shown in the video, ensuring you have the most up-to-date instructions for a flawless installation.
• 🎥 Installation Videos: Visual instructions to help you through the process.
• 🛠️ Parts Included and Tools Needed: A quick list of everything you'll need to get started.
• 📝Step-by-Step Instructions: Clear, easy-to-follow directions.
• ⚠️ Special Notes: Important information and considerations for your installation.
• 🛠️ Common Troubleshooting Solutions: Quick and effective fixes for common installation and performance issues.

Table of Contents

• Important Updates
• Installation Video
• Parts Included
• Tools Needed
• Step 1: Disassembling the Dash
• Step 2: Disassembling Your Tacoma
• Step 3: Routing the Power Wire
• Step 4: Routing the Main Harness
• Step 5: Making Connections to Your Head Unit
• Step 6: Installing the Bass Control Knob
• Step 7: Reinstall Your Head Unit
• Step 8: Connecting the Ground Wire
• Step 9: Modifying the Rear Storage Compartment
• Step 10: Installing the Rear Storage Compartment
• Step 11: Connecting the Power Wire to the Battery
• Amplifier & Subwoofer Settings - Reference Only
• Step 12: Testing System Functionality
• Step 13: Reassembling Your Tacoma
• Common Troubleshooting Solutions

📢 Important Updates & Notes

Update (September 2026): Factory Head Unit Installations
If you have a factory head unit, please disconnect the RCA connections and connect the two red 4-pin connectors directly to each other. Then, press the SPIN/REM button on the PWE-S8 so that SPIN is pressed IN and enabled.

Update (September 2026): Video Installation Notes
At 51:07 in the video, a separate installation guide is referenced. This guide is no longer applicable. Please follow this web-based installation guide for the most current instructions.

At 53:00 in the video, we walk through adjusting the amplifier settings. You can skip this step, as we now pre-set the amplifier settings before your bundle ships.

At 54:21 in the video, a third mounting bolt hole is referenced. This bolt hole is no longer required with the updated kit and can be ignored.

🎥 Installation Video

🛠️Parts Included:

• Amplifier assembly:
• Vehicle specific mounting bracket
• Alpine PWE-S8 powered subwoofer
• Alpine KTA-450 4 channel amplifier
• AudX T-Harness
• Main harness
• RCA adapters
• Power Cable
• 10 Zip Ties
• 10mm Ground Bolt
• Female and male bullet connector

🛠️Tools Needed:

• Panel removal tool
• 10 mm socket
• 12 mm socket
• 14 mm socket
• 3 mm Allen
• Ratchet wrench
• Socket extension
• Phillips head screwdriver
• Zip ties
• Razor knife
• Wire fish
• Wire brush

📝Step-by-Step Instructions

Step 1: Disassembling the Dash

• Pull the outer dash trim straight back toward you to remove it.
• Loosen the four 10mm bolts securing the radio bracket

Step 2: Disassembling Your Tacoma

• Remove the driver-side door sill by pulling straight up.
• Remove the driver-side kick panel:
  • Twist the button retainer counterclockwise to remove it.
  • Pull the kick panel out to detach it.
• Remove the driver-side rear door sill by pulling straight up.
• Remove the lower seat belt screw cover on the B-pillar.
• Use a 14 mm socket to remove the bolt securing the lower seat belt mount.
• Pull back the weather seal on both sides of the B-pillar.
• Use a panel tool to release and remove the B-pillar cover.
• Remove the rear seat headrest on the driver side.
• Flip the driver-side rear seat down and remove the two screw covers on the lower part of the seat.
• Use a 14 mm socket to remove the two mounting bolts from the lower part of the seat.
• Remove the seat back and set it aside.
• Use a 12 mm socket to remove the two bolts on the bracket next to the C-pillar and remove the bracket.
• Remove the rear storage pocket:
  • Use a 10 mm socket to remove the two or three bolts securing the plastic compartment.
  • Remove the plastic compartment.
• Pull back the weather seal from the C-pillar.
• Gently pull out on the C-pillar cover to remove it.

Step 3: Routing the Power Wire

• The kit includes a spyder-wrapped power wire with an inline fuse.
• Open the hood and secure it in place.
• Begin with the ring terminal near the positive battery terminal.
• Route the power wire along the driver’s side fender, toward the firewall, and through the driver-side firewall grommet.

• Use a utility knife to cut an "X" in the grommet.
  • ⚠️Note: Many Toyota firewall grommets have both an exterior and interior membrane, so ensure you cut through both while avoiding damage to any vehicle wiring.
• To make routing easier, you may use a wire fish to pass the blue bullet connector end of the power wire into the vehicle’s cab.
• Once the power wire is inside, pull the slack into the driver’s floorboard.
• Continue routing the power wire through the factory wiring channel along the driver’s side, toward the rear seat.
• Secure any loose wiring in the engine bay using the provided zip ties.

Step 4: Routing the Main Harness

• Begin by connecting the amplifier and subwoofer near the area where the rear storage cubby was removed.
• Route the opposite end of the main harness (with the T-harness end) as follows:
  • Start along the bottom of the C-pillar and follow the factory wiring channel near the driver-side rear door.
  • Continue through the factory wiring channel under the B-pillar and along the wiring channel near the driver-side front door until you reach the front seat mount support.
  • Route the T-harness end of the main harness under the carpet toward the transmission tunnel.
  • Continue along the floor toward the front side of the center console (toward the dash).

• Guide the T-harness up into the lower dash cavity and toward the radio.
• At this stage, fully remove the radio to access the necessary connections.
• Run the T-harness inside the dash toward the main radio connections.

Step 5: Making Connections to Your Head Unit

Making connections to your 2016-2019 head unit:

Factory Head Unit:

• Disconnect the 10-pin and 6-pin connectors from the back of the head unit.
• Connect the male end of the AudX T-Harness to the 10-pin and 6-pin locations on the back of the head unit.
• Connect the 10-pin and 6-pin connectors from the vehicle to the female end of the AudX T-Harness.

Aftermarket Head Unit:

• Front Speakers:
  • White to White
  • Grey to Red
• Rear Speakers:
  • Green to White
  • Purple to Red
• Subwoofer:
  • White to White
  • Red to Red
• Disconnect the 10-pin and 6-pin connectors from the back of the head unit.
• Connect the male end of the AudX T-Harness to the 10-pin and 6-pin locations on the back of the head unit.
• Connect the 10-pin and 6-pin connectors from the vehicle to the female end of the AudX T-Harness.
• Connect RCA cables from the AudX T-Harness to the RCA outputs on the aftermarket radio.

Making connections to your 2020-2023 head unit:

Factory Head Unit:

• Disconnect the 10-pin connector from the back of the head unit.
• Connect the male end of the AudX T-Harness to the 10-pin location on the back of the head unit.
• Connect the 10-pin connector from the vehicle to the female end of the AudX T-Harness.
• Use the provided remote wire T-harness inline with the AM/FM connection from the back of your head unit.
  • Disconnect the AM/FM antenna connection from the back of the head unit.
  • Connect the female end of the T-harness to the male end coming from your dash.
  • Connect the male end of the T-harness back into your factory head unit.
  • Connect the blue remote wire (female bullet connector end) to the blue remote wire from the main harness.

Aftermarket Head Unit:

• Front Speakers:
  • White to White
  • Grey to Red
• Rear Speakers:
  • Green to White
  • Purple to Red
• Subwoofer:
  • White to White
  • Red to Red
• Disconnect the 10-pin connector from the back of the head unit.
• Connect the male end of the AudX T-Harness to the 10-pin location on the back of the head unit.
• Connect the 10-pin connector from the vehicle to the female end of the
  AudX T-Harness.
• Use the provided bullet connectors to connect the remote turn-on wire (Blue with White Stripe) to the aftermarket head unit.
• Connect the RCA cables from the AudX T-Harness to the RCA outputs on the aftermarket radio.

Step 6: Installing the Bass Control Knob

• Use the provided switch blank to install the bass knob.
• Secure the knob in place using the provided nut, then attach the knob to the dial.

Step 7: Reinstalling Your Radio

• Ensure that all previously disconnected connections are securely reconnected.
• Place the head unit back into the dash and secure it using the four factory 10mm bolts.
• Do not fully reassemble the dash yet—functionality should be tested before completing the installation.

Step 8: Connecting the Ground Wire

• Use the provided ground wire to connect the ring terminal to the factory ground located under the rear middle seat racket
  
• Before securing the ground connection, thoroughly clean the grounding location with a wire brush to expose bare vehicle metal. There should be no paint, coating, debris, or other material between the ring terminal and the bare metal.
• Tighten the ground connection securely and verify that the ring terminal does not move.

Step 9: Modifying the Rear Storage Compartment

• Trim the left side of the rear plastic compartment toward the center of the truck.
• A 2.5-inch hole saw can be used as an alternative method.

• Remove the trimmed plastic piece.

Step 10: Installing the Rear Storage Compartment

• Reinstall the C-pillar trim and press it into place.
• Place the rear storage compartment back into the truck.
• Route the main harness through the opening in the plastic.
• Connect the main Alpine harness to the amplifier by connecting the black 22-pin connector.

• Secure the amplifier bracket to the plastic compartment using one of the provided bolts.
  • ⚠️Note: Some vehicles may not have the lower bolt position.

• Position the subwoofer near the storage cubby and connect it to the subwoofer.
• Connect the White 14-pin connector to the subwoofer.
• Connect the RCA cables from the main harness to the subwoofer:
  • Red to Red
  • White to White

• Slide the subwoofer into the lower amplifier bracket.
• Secure the subwoofer bracket to the factory mounting locations using the provided bolts and standoff spacers.

Step 11: Connecting the Power Wire to the Battery

• Use a 10 mm or 12 mm wrench to remove the nut from the positive battery terminal.
• Place the ring terminal from the Alpine power wire onto the positive terminal and secure it with the factory nut.
• ⚠️ Note: A small spark may occur when connecting the ring terminal to the battery—this is completely normal.

Amplifier & Subwoofer Settings - Reference Only

⚠️ Reference Only: Your amplifier and subwoofer settings are pre-set by Trail Grid Pro before your kit ships. You do not need to adjust these settings during installation. The settings below are provided only as a reference in case you need to verify or restore them.

Subwoofer (PWE-S8) Settings:

Factory Head Unit Amplifier Settings:

Aftermarket Head Unit Amplifier Settings:

Step 12: Testing System Functionality

• Power on your vehicle and verify that all components are functioning properly.
• Play a song that will run continuously for a few minutes.
• Check the Balance/Fade settings to ensure all speakers are playing correctly.

Once you have confirmed that your system is working and the gains are adjusted to your preference, reassemble your vehicle and enjoy your newly amplified system!

Step 13: Reassembling Your Tacoma

• Reinstall the weather seal around the rear door.
• Reattach the seat bracket for the rear seat and secure it using the factory 12mm bolts.
• Reinstall the seat back and secure it with the factory 14mm bolts.
• Replace the bolt covers on the lower part of the back seat.
• Flip the seat up and reinstall the headrest.
• Press the B-pillar trim back into place.
• Secure the weather seal around the B-pillar.
• Tighten the 14mm bolt that secures the bottom seat belt mount.
• Reinstall the driver-side kick panel and secure it with the button retainer.
• Press the driver-side door sill and rear door sill back into place.
• Tighten the four 10mm bolts securing the radio.
• Press the dash trim back into place to complete reassembly.

Congratulations on installing your new Alpine 4 Channel Amplifier and Powered Subwoofer kit!

🛠️ Common Troubleshooting Solutions: Experiencing issues with your installation? Try these steps before reaching out for support.

1. Check the Connections Behind the Head Unit

If you have a factory head unit:

• Ensure all main vehicle connectors are fully seated and locked into place.
• Verify the remote wire from the amplifier harness is properly connected.
• Inspect the harness connections for any loose terminals, bent pins, or wires that may have backed out of the connectors.
• Make sure no wiring or connectors are pinched behind the head unit when it is installed.

If you have an aftermarket head unit:

• Ensure all main vehicle connectors are fully seated and locked into place.
• Verify that the RCA connections are fully plugged in.
• Check that the remote wire from the amplifier harness is connected to the radio harness.
• Make sure the subwoofer output is turned ON in the head unit settings menu.
• Verify that the front and rear RCA connections are connected to the correct outputs on the head unit, if applicable.
• Inspect the harness connections for any loose terminals, bent pins, or wires that may have backed out of the connectors.
• Make sure no wiring or connectors are pinched behind the head unit.

2. Check the Alpine Amplifier Settings

• Remove and clean the ground connection. Disconnect the ground and thoroughly clean the grounding location with a wire brush. There should be no paint, coating, debris, or other material between the ground terminal and bare vehicle metal. Once cleaned, reconnect the ground and make sure it is tight and secure.
• Confirm that the front and rear gain settings are turned low/off.
  
• Double-check the dip switches on the amplifier—the recommended settings can be found in the installation guide.

3. Check the Subwoofer Settings

• Make sure the input selector is set correctly for your head unit:
  • Aftermarket head unit: Set the input selector to REM (Remote).
  • Factory head unit: Set the input selector to SPIN, making sure SPIN is pressed IN and is not sticking out.
• Verify that the blue indicator light is on.
• Check that the gain and crossover dials are set to low/off.
• Verify the correct audio connections:
  • Aftermarket head unit: Ensure the RCA adapter from the amplifier harness is connected to the RCA inputs on the subwoofer.
  • Factory head unit: Disconnect the RCA connections and connect the two red 4-pin  connectors directly into each other.

If the RCA adapter is not connected and you have an aftermarket head unit, follow these steps:

• Locate the red 4 pin connector on the main harness near the subwoofer.
• Disconnect the male and female ends of the red 4 pin connector.
• Find the RCA adapter in the "Extra Parts" bag.
• Attach the male 4-Pin connector from the RCA adapter to the female red 4 pin connector.
• Connect the RCA's to the RCA inputs on the subwoofer.
• Play music and adjust the subwoofer gain to your preferred level.

4. Bass Knob 

If your bass knob is not working with a factory head unit, please verify the following:

• Make sure the PWE-S8 is set to SPIN.
• Make sure the RCA connections are disconnected.
• Confirm that the two red 4-pin connectors are connected directly to each other.

Please refer to Troubleshooting Step 3 for additional details.

5. Optimizing Sound Quality and Tuning Your System

Once you’ve confirmed all connections and verified that the amplifier and subwoofer are functioning properly, follow these recommendations to fine-tune your system.

• If using a factory head unit, keep in mind that the audio signal level increases as the volume is raised.
• Setting the amplifier gain too high can cause distortion or may cause the amplifier to enter protection before reaching higher volume levels.
• Gain should be used to properly match the amplifier to the incoming audio signal, not simply as a volume control.

Recommended Tuning Process:

• Turn the gain adjustments on both the amplifier and subwoofer to their lowest settings.
• Play a clean, high-quality song that will continue playing for several minutes.
• Gradually increase the head unit volume to approximately 75% of maximum volume.
• If you hear distortion, experience audio cutout, or the amplifier enters protection before reaching this level, stop increasing the volume and refer to the troubleshooting section before continuing.
• Using a small flathead screwdriver, slowly increase the Front Gain until you reach your desired output level without distortion.
• Repeat the process for the Rear Gain.
• Slowly adjust the Sub Gain to blend the PWE-S8 with the rest of the system.
• Fine-tune the subwoofer crossover based on your listening preference.

Important: Avoid continuing to increase the gain or volume if you hear distortion, popping, crackling, or experience complete audio cutout. These symptoms should be addressed before continuing with tuning.

Final Adjustments & Sound Tweaks

• If you hear distortion, clipping, popping, crackling, or experience audio cutout, stop increasing the volume or gain and refer to the Troubleshooting section before continuing.
• Adjust the EQ settings within your head unit to fine-tune the sound to your preference.
• Avoid excessive bass or EQ boost, as this can cause distortion or place additional demand on the amplifier and speakers.
• If using an aftermarket head unit, make sure the subwoofer output is turned on in the head unit settings menu.
• Make small adjustments at a time and test the system before making additional changes.

Contact Us

If you're still encountering difficulties and need additional troubleshooting support, please reach out using this contact form, and someone will get in touch as soon as possible.