Alpine 4 Channel Amplifier and Powered Subwoofer Installation Guide | 2010-2024 4Runner

Note: This kit is NOT compatible with Factory JBL amplified systems.

Installation Video

Parts Included:

• Amplifier assembly:
• Vehicle specific mounting bracket
• Alpine PWE-S8 powered subwoofer
• Alpine KTP-445U 4 channel amplifier
• T-Harness
• Main harness
• RCA adapters
• Power Cable
• 10 Zip Ties
• 10mm Ground Bolt

Tools Needed:

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

To ensure that your items arrived un-damaged we have made a procedural change to the assembly of the kit. 

Please use the following instructions to complete final assembly of your Alpine 4 Channel Amplifier and Subwoofer kit from Trail Grid Pro.

Step 1

• Remove the subwoofer from the packaging.
• Place the subwoofer on a flat table with the speaker grille facing down to the table.
• Orient the subwoofer so that the Alpine sticker and subwoofer controls are facing you.

Step 2

Installing the Left bracket:

Remove the bracket labeled PSU-BKT FRN L from the packaging and place it on the table as shown below:

• Remove the amplifier from the packaging and place the amplifier onto the Left bracket.
  • Ensure that the gain controls are facing you. 

• Use the provided screws from the “Amplifier Mounting Screws” bag to secure the amplifier to the bracket.

• Rotate the bracket over and place on the Left side of the subwoofer.

• Use the provided screws in “Bracket Mounting Screws” bag to secure the Left bracket.
  • Assembly: 1 bolt, then place a split washer on the bolt and then a flat washer, Repeat 8 times.
• Secure the Phillips head bolts, be sure not to over tighten. 

Step 3

Installing the Right bracket:

• Remove the bracket labeled PSU-BKT FRN R from the packaging and place it on the subwoofer as shown below:
  

• Use the provided screws in “Bracket Mounting Screws” bag to secure the Right bracket.
  • Assembly: 1 bolt, then place a split washer on the bolt and then a flat washer, Repeat 8 times
  • Secure the Phillips head bolts, be sure not to over tighten.
    

Step 4

Removing your radio:

• Remove the two side panels on either side of the HVAC control by pulling straight back.
• Remove the HVAC control panel by pulling straight out.
• Remove the wire holder using a panel removal tool.
• Disconnect the wire connector from the back of the panel.
• Loosen the four 10mm bolts that secure the radio to the dash. 
• Do not completely remove the radio, we will need to disassemble other areas before we need access to the rear of the radio. 

Step 5

Remove the center console:

• If you have a manual 4WD gear shifter, remove the handle by twisting counter clockwise.
• Remove the gear shifter handle by twisting counter clockwise. 
• Lift up on the shifter panel to remove.
• Disconnect any wire connections before fully removing.
• Remove the lower trim panel using a pry tool to lift out the plastic trim cover.

• Remove the two 10mm bolts that secure the trim panel containing the 12V outlet and USB. 

• Pull straight out to release the retaining tabs.
• Disconnect any connectors before fully removing. 

Step 6

Remove the passenger front seat: 

• Remove the passenger front door sill plate by lifting straight up.
• Remove the plastic nut holding on the passenger side kick panel.
• Remove the kick panel by pulling out. 
• Remove the plastic covers from the front seat bolt brackets. 
• Remove the front seat bolts using a 14mm socket.
• Move the seat to the forward position.
• Remove the plastic covers from the rear of the front seat brackets.
• Remove the front seat bolts using a 14mm socket.
• Move the seat back to the middle position and lean the seat back to access the bottom.
• Remove the connectors by depressing the tabs.
• Remove the seat from the vehicle. 

Step 7

Routing the power wire:

• Provided in the kit is a spyder wrapped power wire with inline fuse. 
• Open and secure the hood.
• Start with the ring terminal near the positive battery terminal.
• Route the power wire along the drivers side fender, across the firewall and towards the passenger side firewall grommet. 
• Locate a spot to cut an "X" in the grommet using a utility knife. Keep in mind that many Toyota firewall grommets have an exterior and interior membrane that you will need to cut through. Take extra care to not damage any other vehicle wiring when cutting your "X."
• You may choose to use a wire fish to help with passing the blue bullet connector end of the power wire into the cab of the vehicle. 
• Once the power wire is through the firewall, pull the slack into the passenger floor board. 
• Secure any loose wire in the engine bay using the provided zip ties. 

Step 8

Routing the main harness:

• Start with the main harness in the area under the front passenger seat.
• Begin with the T-harness end of the main harness and route it towards the head unit. 
• Begin by going under the carpet directly towards the gear shifter. 
• Once you are into the transmission tunnel area continue towards the front of the vehicle.

• At this point, you will want to remove the radio fully to gain access to the connections. 
• Continue running the T-Harness up the inside of the dash and towards the main radio connections. 

Step 9

Making connections to your 2010-2019 head unit:

• Factory Head Unit:
• Disconnect the 10 pin & 6 pin connector from the back of the head unit.
• Connect male end of the Alpine T-Harness to 10 pin & 6 pin locations in the back of head unit. 
• Connect 10 pin & 6 pin connectors from vehicle to female end of the Alpine T-Harness.
• Aftermarket Head Unit:
• Disconnect the 10 pin & 6 pin connector from the back of the head unit.
• Connect male end of the Alpine T-Harness to 10 pin & 6 pin locations in the back of head unit. 
• Connect 10 pin & 6 pin connectors from vehicle to female end of the Alpine T-Harness.
• Connect RCA's to RCA outputs from aftermarket radio:
• Front
• White to White
• Grey to Red
• Rear
• Green to White
• Purple to Red
• Sub
• White to White
• Red to Red

Making connections to your 2020-2024 head unit:

• Factory Head Unit:
• Disconnect the 10 pin connector from the back of the head unit.
• Connect male end of the Alpine T-Harness to 10 pin location in the back of head unit. 
• Connect 10 pin connector from vehicle to female end of the Alpine T-Harness.
• Connect Alpine 2 pin connector to the cigarette lighter harness.
• Disconnect the harness directly from the back of the cigarette lighter. 
• Connect the male end of the 2 pin T-harness to the cigarette lighter.
• Connect the female end of the 2 pin T-harness to the factory wiring for the cigarette lighter. 
• Aftermarket Head Unit:
  • Disconnect the 10 pin connector from the back of the head unit.
  • Connect male end of the Alpine T-Harness to 10 pin location in the back of head unit. 
  • Connect 10 pin connectors from vehicle to female end of the Alpine T-Harness.
  • Use provided bullet connectors to connect remote turn on wire (Blue with White Stripe) to your aftermarket head unit. 
  • Connect RCA's to RCA outputs from aftermarket radio:
  • Front
  • White to White
  • Grey to Red
  • Rear
  • Green to White
  • Purple to Red
  • Sub
  • White to White
  • Red to Red

Step 10

Replace your radio into the dash:

• Now that your main wiring harness is connected, make sure that any other connections that may have been removed are reconnected. 
• Place your head unit back into the dash and secure with the four factory 10 mm bolts. 
• Do not completely reassemble your dash at this time. We will want to test functionality before completely putting the truck back together. 

Step 11

Connecting the ground wire:

• Using the provided Alpine ground wire, attach the ring terminal to the factory ground under the passenger seat. 
• If not factory ground bolt is present, use the provided bolt to secure the ring terminal from the ground wire to the pre-thread hole under the passenger seat. 

Step 13

Routing the Alpine bass control knob:

• If you are using the PSU kit with a factory head unit and would like to control the bass, you will need to place and connect the provided control knob. 
• Use the provided velcro to place the bass control knob in your desired location. 
• Route the wire to the subwoofer/amplifier assembly and connect the 3.5mm headphone jack into the subwoofer. 
• Secure any extra or loose wire with zip ties as needed. 

Step 14

Placing the subwoofer/amplifier assembly in the vehicle:

• Place the subwoofer/amplifier assembly on the floor under the front passenger:
• The angled end of the brackets will go towards the front of the vehicle. 
• When properly placed, the holes in the legs of the bracket will line up with the factory seat bolts and locating pins from the seat.

• Make the connections from the Alpine main harness to the subwoofer and amplifier:
• Connect the White 14 pin connector to subwoofer.
• Connect the RCA's from the main harness to subwoofer:
• Red to Red
• White to White
• Connect the Black 16 pin connector to amplifier.
• Connect the Black 10 pin connector to amplifier. 

• Connect the bullet connector from the power wire that you ran from the battery earlier and connect to the yellow wire from the main harness.

• Use the provided zip ties to secure any extra or loose wires. 

Step 15

Connect the power wire to the battery:

• Use a 10mm or 12mm wrench to remove the nut from the positive battery terminal. 
• Place the ring terminal from the Alpine power wire on the positive terminal and secure with factory nut. 
• It is completely normal to get a small spark when placing the ring terminal on the battery. 

Step 16

Test your system functionality:

• Power on your vehicle and test functionality. 
• Find a song that will play continuously for a few minutes:
• Check Balance/Fade setting to ensure all speakers are playing appropriately
• Below is the recommended amplifier setting for use with a Factory Head Unit:

• Below is the recommended amplifier setting for use with an Aftermarket Head Unit:

Once you have confirmed that your system is working and you have set the gains to your liking, reassemble your vehicle and enjoy your new amplified system!

Step 17

Replacing the front passenger seat:

• Once you are satisfied with the setting of your amplifier and subwoofer it is time to replace the front seat. 
• Make sure all loose wires are secured and that the brackets on the subwoofer/amplifier assembly are lined up with the mounting holes in the floorboard. 
• Gently place the seat into position.
• Replace any wiring harnesses that were disconnected during disassembly. 
• Start the four 14mm bolts that secure the seat by hand.
• Use a 14mm socket to fully tighten the seat bolts. 
• Replace the plastic covers over the seat bolts.

Step 18

Replacing trims panels and center console:

• Replace the kicker panel at the bottom of the A pillar and secure the plastic retention nut. 
• Replace the door sill panel. 
• Replace the plastic trim panel below the glove box. 
• Reconnect any wiring connector to the center console trim.
• Place the console trim into place and press to secure. 
• Replace the lower trim panel containing the 12V outlet and USB.
• Secure with two 10mm bolts.

Step 19

Replace the radio and center dash trim:

• Fully tighten the four 10mm bolts securing the head unit. 
• Reconnect the wiring connector to the HVAC panel and press into place. 
• Attach side trim panels.

Troubleshooting:

Check the following items behind the head unit:

Factory head unit:

• Are the main vehicles connectors fully seated?
• Is the remote wire from the amplifier harness connected to the radio with a T-tap or T-Harness?
• If you're using a T-tap do you have a solid contact between the wires? You will know if you have a solid connection when the blue indicator light on the subwoofer is illuminated.

Aftermarket head unit:

• Are the main vehicles connectors fully seated?
• Are the RCA connections fully seated?
• Is the remote wire from the amplifier harness connected to the radio harness?
• Please ensure that the subwoofer output is turned on in the settings menu of the head unit.

Check the following items at the amplifier:

• Are the front and rear gains set to low/off?
• Double check the dip switches on the amplifier, the recommended settings can be found in the installation guide above.

Check the following items on the subwoofer:

• Is the input selector in the out position and set to "Remote"?
• Do you have a solid blue indicator light?
• Check the gain and crossovers dials, are the dials set to low/off?
• Do you have the RCA adapter connected from the amplifier harness to the RCA connections on the subwoofer?
• If not, please use the following instructions to add the subwoofer RCA to the main harness:

1. 1. Locate the red 4 pin connector on the main harness near the subwoofer.
   2. Disconnect the male and female ends of the red 4 pin connector.
   3. Connect the RCA adapter (located in the spare parts bag), attach the male 4 pin connector from the RCA's to the female red 4 pin connector.
   4. Connect the RCA's to the RCA inputs on the subwoofer.
   5. Adjust subwoofer gain on subwoofer with music playing to achieve preferred setting.

Once you have verified that the connections are correct and that the amplifier and subwoofer are working, here are a few more items to consider:

• If you are using this kit with a factory head unit, it is important to note that the factory unit output is voltage regulated. This means that the higher the volume number, the more power the head unit puts out. If you have the amplifier gains set to high with a low volume number on the head unit, when you increase the volume on the head unit the door speakers will peak out before enough signal has been sent to the subwoofer to produce an a desirable level of bass.
• Our recommendation is the tune the amplifier and subwoofer using the following steps after installation is complete:
  • Turn the gain adjustments on the amplifier and subwoofer all the way to the left or the lowest setting.
  • Find a song that will play for at least a few minutes.
  • Turn up the volume on your head unit to about 75% of the MAX volume.
  • Using a small flathead screwdriver adjust the Front gains setting on the amplifier until your desired sound level is reached.
  • Repeat the same for the Rear gains setting on the amplifier.
  • Repeat once more for the Sub gain setting on the subwoofer.
  • Adjust the crossover setting on the subwoofer to desired level.
• This will set the overall sound level for your vehicle. If you start to notice distortion or that the sound is clipping or stopping you have set your gains to high!
  • You can further adjust to your liking using the EQ settings within your head unit.
• If you have an aftermarket head unit, please ensure that the subwoofer output is turned on in the settings menu of the head unit.

Congratulations on installing your new 4 Channel Amplifier and Powered Subwoofer Kit from
Trail Grid Pro!