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PAC AmpPRO AP4-FD21 Amplifier Replacement Interface

Allows seamless replacement of the premium factory amp in select 2012-up Ford vehicles

8 Reviews | 6 questions - 12 answers

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Our take on the PAC AmpPRO AP4-FD21 Amplifier Replacement Interface

You can make a less-than-ideal premium factory system actually sound premium by replacing the weak factory amplifier with a more powerful aftermarket amp. PAC's AmpPRO interface consists of a module and a vehicle-specific T-harness that make the job much easier. Now, you can install an amplifier of your own without losing any of your vehicle's factory audio features like warning chimes, navigation prompts, and Bluetooth functions.

Your amp will sound better than the factory amp

You can make a less-than-ideal premium factory system actually sound premium by replacing the weak factory amplifier with a more powerful aftermarket amp. PAC's AmpPRO interface consists of a module and a vehicle-specific T-harness that make the job much easier. Now, you can install an amplifier of your own without losing any of your vehicle's factory audio features like warning chimes, navigation prompts, and Bluetooth functions.

Simple to install

The package's T-harness plugs into the factory radio and vehicle harness. The small module fits behind the dash, converting your radio's speaker outputs into six preamp-level outputs ready for connection to your amp. The factory radio controls, such as volume, balance, and fade, will work as before for your front and rear speakers. A separate wired remote level control lets you adjust the volume of the subwoofer channels from your front seat. An optional add-on module, PAC's APA-TOS1 adapter, provides an optical digital output for your high-end digital processors and amplifiers to handle.

An app for tweakers

After downloading the AmpPRO PC App and connecting to your Windows-run PC via USB, you can access the factory 3-band parametric equalizer (EQ) and customize the tone of your system to perfection. The app also lets you adjust chime volume, the system's minimum volume level, and update the product firmware when needed.

Important Note: This AmpPRO interface simplifies the installation of a car amplifier (not included). You'll also need to purchase anything required to install your new amp: an amp wiring kitspeaker wire (to replace factory wiring), and RCA cables. Your factory amp must be working and connected to the factory radio for this interface to work.

Product Highlights:

  • amplifier replacement module and T-harness
  • works with select 2012-up Ford vehicles with a premium sound system
  • 6-channel RCA outputs (front, rear, subs)
  • switchable 5- or 4-volt RMS output
  • retains factory radio controls and audio features
  • wired remote level control for sub channels
  • remote turn-on lead for amplifiers
  • AmpPRO PC App, available from PAC, lets you adjust minimum and chime volumes and 3-band EQ via your Windows-run PC
  • optional TOSLINK adapter provides digital output
  • warranty: 1 year
  • Our 60-day money-back guarantee

What's in the Box:

  • Amplifier integration interface module
  • T-harness
  • 6' Rotary-knob cable
  • Rotary-knob
  • Installation Instructions

Critchfield has the best technology on the market and professional staff. Crutchfield knew exactly what I needed in my F-150 to install an after market Amp on my truck. Thank you and keep up the great work! Ed Tuccio

Ed, Puyallup, WA


PAC AmpPRO AP4-FD21 Amplifier Replacement Interface Reviews

Average Customer Review(s):

(8 Reviews)

PAC AmpPRO AP4-FD21 Amplifier Replacement Interface

Ed from Puyallup, WA on 2/26/2019

2014 Ford F-150 Lariat
Crutchfield Customer Review (What's this?)

Critchfield has the best technology on the market and professional staff. Crutchfield knew exactly what I needed in my F-150 to install an after market Amp on my truck. Thank you and keep up the great work! Ed Tuccio

Pros: Up to date software and staff

Cons: ..

PAC AmpPRO AP4-FD21 Amplifier Replacement Interface

Crutchfield customer from Falls Church, VA on 12/30/2018

2016 Ford F-150 XLT
Crutchfield Customer Review (What's this?)

Great alternative to spending $1,000 to replace headunit!! I love it



Works w/ Ford Flex Sony system

Jordan from Eau Claire, WI on 12/17/2018

2013 Ford Taurus
Crutchfield Customer Review (What's this?)

A wonderful product! Very happy to have found this. I can confirm that it does work in my 2013 For Flex w/ Sony system as well, despite not being listed. Made the install a breeze.

Pros: -Easy to install -Bass knob is handy -Literally plug and play -Plenty of excess wiring to make mounting easy

Cons: -Volume decrease when backup sensor starts going off very slightly delayed - only a fraction of a second

PAC AmpPRO AP4-FD21 Amplifier Replacement Interface

Crutchfield customer from Winnie, TX on 12/10/2018

2016 Ford F-150 Lariat
Crutchfield Customer Review (What's this?)

The Amp pro works perfectly in my 2016 F-150 with the Sony system. easy to install.



Great integration solution

Chad from Kentucky on 9/4/2018

2016 Ford Taurus
Crutchfield Customer Review (What's this?)

I'm using this in my 2016 Ford Taurus SHO. Crutchfield says it's not compatible, but they are wrong. It works perfectly, and I expect it would work in a lot more Sync3 equippped Fords with the Sony system that Crutchfield and Pac say are not compatible. I had a feeling it would work because the ACM is the same from 2013 to present, and the APIM has the same pinout whether it's Sync3 or MyFordTouch. This module just piggybacks on those two modules, so it should work the same in anything with a Sony ACM and a Sync APIM. This thing is awesome compared to the piece of garbage Rockford Fosgate DSR1 I just sent back. My stereo actually sounds like it should, not all muddy and artificial like before, and the amp turn on, steering wheel controls, Sync prompts, backup sensors, etc all work properly. I used the optional optical output with a dedicated dsp, and there is no noise, so I can't speak to how it works stand alone noise wise.

Pros: Sounds great, all original functions retained perfectly

Cons: Pain in the butt to install since the dash has to be ripped apart.

Noisy little bugger

Joshua from College Station, TX on 8/1/2018

2018 Ford Edge
Crutchfield Customer Review (What's this?)

If you're looking for a way to easily integrate an after market amp into your Sony system, this will do that. It does keep all the dings and Nav voice. What it adds is why it got 3 stars. Whenever I change songs it makes a weird noise sometimes, and this thing introduces some noise! I mean very very noticeable noise. I'm running Mosconi Zero amps, Focal BE and Illusion Audio Carbon speakers, all going into a Mosconi 8to12 Aerospace DSP. So I've got some nice equipment, and I was running it all on the Forscan Sony hack, but it has some weird problems, it would power on the amp through the RCA's, and sometimes it would pop when shutting off. So I thought why not try this. Well I went from an almost zero noise floor to some crazy hiss coming through my speakers, at first I thought maybe I got a bad unit, so I swapped it out a different one, still the same thing. This is all running over Stinger 9000 series RCA's, which are very high quality RCA's. The only thing that solved it was buying a good optical add-on cable. (Spending a lot on an optical cable isn't necessary, but you will audibly hear the difference). I went with Audioquest Carbon. After doing all that it sounds much better. My problem with it is I shouldn't have to buy an additional add on module, an optical cable, and reconfigure my whole system (optical cables require adjustments of amp gains) just to make this thing work as it should.

Pros: -Easy to use -Harness is of nice thick gauge wire

Cons: -Audible hiss -Weird noise when changing songs.

PAC AmpPRO AP4-FD21 Amplifier Replacement Interface

Crutchfield customer from Anaheim, CA on 6/19/2018

2013 Ford F-150 Platinum
Crutchfield Customer Review (What's this?)

I recommend the Amppro. I used it in 2013 F-150 and it works great. I also got the optional optical connection. System sounds are the right volume and the amps receive a clean signal.



Just buy it!

Bryce H. from Virginia Beach, VA on 8/12/2017

2004 Dodge Ram 1500

Amazing product. Installed 3 of them so far for my clients with F-150's. If you have the chance to get the Optical Toslink output add-on module, do it! Your DSP will thank you. Can't recommend this unit enough.

Pros: Sound Quality, Optical Output, no loss of NAV guidance, SYNC commands etc..., small form factor, prewired T-Harness with Tessa Tape!. Perfect!

Cons: Sony amplifier needs to stay in the vehicle (plugged in) in order for the OEM volume control on the head unit to continue working. PAC has told me they are working on a new firmware fix for that.


Hands-on research

Product Research


Amplifier Integration Interface: The PAC AmpPRO AP4-FD21 simplifies the installation of aftermarket amplifiers in select Ford vehicles with data-bus controlled factory sound systems. With the AmpPRO AP4-FD21, you can improve your vehicle's audio performance while keeping an original radio's fit, finish, and features.


  • The factory radio and factory amplifier must remain connected in the vehicle and be operational in order to use the PAC AmpPRO interface.
  • If you are only using the PAC AmpPRO interface to add a subwoofer amplifier, the factory amplifier will still power the other speakers in the vehicle.

Vehicle Compatibility: The PAC AmpPRO AP4-FD21 amplifier integration interface is compatible with the following 2013-2017 Ford vehicles with a data-bus controlled factory premium sound system.

Make Model Year
Ford Edge 2015-2017
Expedition 2015-217
Explorer 2011-2017
F- Series (150/250/350/450/550) 2013-2017
Focus 2012-2017
Fusion 2013-2016
Taurus 2013-2015
Note: This interface is only compatible in vehicles equipped with a data-bus controlled premium sound system. To verify compatibility, look for a Sony badge on the door speakers, center speaker, or factory sub woofer. If this brand is not shown, check for the presence of a center speaker or subwoofer.

6Ch Pre-Outs: The PAC AmpPRO AP4-FD21 provides a 6-channel pre-amp output for use with aftermarket amplifiers. Using the full-range, fixed level factory radio output, in conjunction with data-bus CAN messages, the AP4-FD21 delivers a variable 5V RMS pre-amp output with fading, balance, equalization, and level control capabilities.

Non-Fading Level Control Knob: Channels 5-6 (Sub) of the AP4-FD21 are non-fading outputs. The output level of channels 5-6 can be controlled using the supplied level control knob. The level control knob comes with a 6' cable which plugs into the interface module and should be mounted in an accessible location.

Data Controlled Remote Turn-On: A data controlled remote amplifier turn on wire is also provided by the PAC AmpPRO AP4-FD21. The remote turn-on is rated at 2A of current. If more current is needed an external relay must be used.

Retained Factory Audio Features: The PAC AmpPRO AP4-FD21 also retains all audio from other vehicle features such as factory Navigation Prompts, Bluetooth, Sync, and Warning Chimes.

Minimum & Chime Volume: If the minimum volume of your factory radio is too loud once the AP4-FD21 is installed, you can manually set the level of the minimum volume using either the programming button on the side of the interface or the factory SWC (Steering Wheel Controls) in conjunction with the supplied level control knob. You can also use AmpPRO PC app. You can also adjust the chime volume level.

AmpPRO PC App: Using the AmpPRO PC App (for Windows PC only) allows you to configure user interface options such as Minimum Volume Level, Chime Volume Level, and a 3-Band EQ from your Windows computer or laptop. The app can also be used to update product firmware.

  • Minimum & Chime Volume Level: From the app you can set the minimum volume level of the factory radio, as well as the chime volume level.
  • 3-Band EQ: Enables the 3-band EQ (Bass-Mid-Treble) with frequency and Q-factory adjustment. The Bass Frequency can be set to 60, 80, 100, or 120Hz; while the Bass Q-Factor can be set to 0.5, 1.0, 1.5, or 2.0. The Mid Frequency can be set to 500, 1k, 1.5k, or 2.5k; while the Mid Q-Factor can be set to 0.75, 1.0, 1.25, or 1.5. The Treble Frequency can be set to 7.5k, 10k, 12.5k, or 15k; while the Treble Q-Factory can be set to 0.75 or 1.25.
  • Firmware: The AmpPRO app will also allow you to update the interface with new firmware as it becomes available.
Note: These AmpPRO PC App settings can be adjusted with the module installed in the vehicle or on the bench. However, it is recommended to make the adjustments with the module installed, and the factory radio on so that the changes can be heard.

Dip Switch: Set dip switch 2 to "ON" to lower the RCA output voltage to 4V. Set the dip switch 2 "OFF" to keep the RCA output voltage at 5V. Dip switches 3-4 are used for troubleshooting Sync & Bluetooth. Dip switch 1 is not used.

Optional Toslink Add-On Module: When used in conjunction with PAC's APA-TOS1 (541APATOS1; sold separately), the AP4-FD21 can provide a variable 2-channel fiber optic digital audio output (toslink). Toslink fiber-optical cable also sold separately.

Optional Amplifier Harness: The APH-FD01 installation harness (541APHFD01, sold separately) simplifies speaker wire connections when using the PAC AmpPRO AP4-FD21 (sold separately) to add an aftermarket amplifier or amplifiers in select 2007-2017 Ford and Lincoln vehicles that feature factory amplified sound systems. The APH-FD01 keeps you from having to cut or modify your vehicle's original factory wiring, providing "plug-n-play" connection at the vehicle's original factory amplifier location (you will need to make hardwire connections at the aftermarket amplifier/s). 

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team. They verify what’s in the box, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.

Q & A

Customer Q&A

Crutchfield asked  
Why did you buy this?

Because it was recommended by my local car audio shop. [ DAVID  Sep 16, 2018 ]
It had plenty of positive feedback on a popular Ford Explorer Audio Forum (2015 Ford Explorer Sport) and was endorsed by one of your knowledgeable technicians. [ Jeremy  Jul 18, 2018 ]
This is the 3rd one of these I've installed because the remote out power turn off has stopped working on both of the previous ones, but have to have it because my whole $5K system won't run in my Explorer without this interface. [ Corey  Jul 13, 2018 ]
to put an amp in my 15 F150 [ Nolan  Apr 12, 2018 ]
Thanks to the support of the service team at Crutchfield. I was advised to choose this product due to my stock Sony sound system my car is equipped with, this product allows me to remove the stock Sony amplifier, and continues to allow the stock head unit to function as it does normally, but with added clarity. And furthermore i can now add more aftermarket equipment to my vehicle in a much simpler and less congested way. [ jonathan  Mar 26, 2018 ]
works in my 2017 F350 [ DAVID  Jan 11, 2018 ]
Nice [ Chris  Dec 22, 2017 ]
This item will allow me to use my factory radio and create a customized high quality sound system and retain all factory functions. [ CALVIN  Oct 01, 2017 ]
Only way to have quality audio in a f150 with Sony package [ Gage  Sep 29, 2017 ]

6 questions already asked

Yes - you can connect the Toslink output of the AmpPro to your DM810 and the DM810 will split the 2 full range channels into 4 full range pairs and one mono pair for your subwoofer. It will also give you level controls between each channel in the PC interface. [ Carl  Dec 12, 2018 ]
Yes, you can use all your output channels. The DSP software processes and routes the signal to the DSP outputs. The optical signal the Amppro puts out is a non fading pure stereo PCM signal. I am using all 8 channels of my JL Audio Twk-D8 DSP with the optical output from the Amppro feeding it. [ CHAD  Dec 12, 2018 ]
That's technically a question which pertains to your DSP, not this PAC adapter. For example, using my JL Audio TWK-D8 I can take the 2 channels (full range) from the PAC AmpPro and map or route those to any combination of EQs and crossovers within the DSP. With 2ch stereo input I can get all 8 channels out of my DSP in any combination I need. Go get super comfy with your DSP documentation and/or software and you'll find your answer. [ Anthony  Dec 12, 2018 ]
Yes all of the output can be used. What I believe you lose is the ability to fade front to rear since the toslink only provides stereo left and right. [ Patrick Van  Dec 12, 2018 ]
If you have the Sony system this will work. If you have the B&O system you need the Nav-Tv [ Cone Computer  Jul 17, 2018 ]
You didn't mention the model of you vehicle but...I believe you should look into PAC AmpPro mode# AP4-FD11. You may have better luck. [ Anthony  Dec 12, 2018 ]
I checked but we didn't get any information as to why this product doesn't work in a 2010. I'd guess its either the connection, the audio transfer method, or maybe both. You might be able to call PAC to see if they have specifics on this product. Their phone number is 800-336-6500. My Bio: [ Paul  Dec 21, 2017 ]  Staff
I don't see this product anywhere in our databases right now and cannot find any information on if we will even carry it. I did put in a request to our merchandising team to pick it up. Hopefully we will! My Bio: [ Paul  Dec 31, 2017 ]  Staff
Short answer, no, this will not work for you. The PAC site states clearly that these interfaces require the amplified/premium OEM Sony sound systems. The reason is that these interfaces sit between the factory amplifier (absent in your system) and the factory stereo interface, and interpret the communications between them. [ Anthony  Dec 12, 2018 ]
I don't know as my truck had the Sony system, which it worked fine with. [ MARC  Nov 30, 2017 ]
If you look on Pac-Audios site they offer a module that plugs into the factory plug and you can wire it directly into an amp without cutting factory wires. [ Cone Computer  Jul 17, 2018 ]
The PAC AmpPRO simply provides the RCA pre-amp outputs you'll need to provide audio to an aftermarket amplifier. When adding a high-powered amp, I definitely recommend running thicker, aftermarket speaker wire to ensure the full power and fidelity from the new amp makes it to the new speakers. [ Ryan  Aug 26, 2017 ]  Staff

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