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Axxess AXDSPX-GM31 Digital signal processor and T-harness — for select 2019-up Chevy and GMC vehicles without a factory amplifier

Item # 120XGM31

Let's face it, your GM vehicle's fancy feature-filled radio doesn't sound that good, but you can't replace it...

Find what Fits your vehicle


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Let's face it, your GM vehicle's fancy feature-filled radio doesn't sound that good, but you can't replace it...

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4 questions - 7 answers

Item # 120XGM31

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About the Axxess AXDSPX-GM31

Buck Pomerantz

Plug in for better sound

Let's face it, your GM vehicle's fancy feature-filled radio doesn't sound that good, but you can't replace it because of all the good things it does. Axxess has come out with this fully-tunable digital sound processor that plugs into your factory radio, so you can add aftermarket amplifiers and transform your vehicle's interior into the sweet-sounding music listening room you want.

Plug in for better sound

Let's face it, your GM vehicle's fancy feature-filled radio doesn't sound that good, but you can't replace it because of all the good things it does. Axxess has come out with this fully-tunable digital sound processor that plugs into your factory radio, so you can add aftermarket amplifiers and transform your vehicle's interior into the sweet-sounding music listening room you want.

Bluetooth® control

You make all your sound adjustments via the Bluetooth connection on your Android or Apple device using Metra's AXDSP-X app. Adjustment features on each channel include a 31-band graphic EQ with high-pass, low-pass, and bandpass filter options. Time delay allows you to align the sound of all your speakers in order to create the perfect sound stage centered on the driver or prime listener.

System options

If you're sending one of the assignable output channels to a sub amp, the AXDSP-X comes with a wired remote bass knob, so you can control the bass from the front. Nine other outputs in the harness allow you to add even more amplifiers and create your own large custom sound system.


Product highlights:

  • digital signal processor and T-harness
  • GM31 harness fits select 2019-up Chevy and GMC vehicles without a factory amplifier
    • plugs into factory radio
    • allows you to add aftermarket amplifiers then tune your system
  • 6 inputs, 10 individually assignable output channels
  • settings adjusted through tablet or smartphone running the AXDSP-X app
  • each channel Features:
    • 31-band graphic EQ
    • high-pass, low-pass, and bandpass filters
    • time delay (up to 10ms)
  • bass knob included
  • chime control for GMC vehicles
  • retains OnStar® voice prompts
  • 10 RCA outputs: front L and R, rear L and R, six assignable (up to 5 volts)
  • warranty: 1 year

What's in the box:

  • DSP Interface module
  • 56-Pin T-harness
  • 16-Pin Output harness (11 female RCAs / 2 bare-ended wires)
  • Remote bass control (attached 5' bare-ended red/black wires)
  • Bass control mounting bracket
  • Two 8mm screws
  • Instruction manual

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More details on the Axxess AXDSPX-GM31

Stacey B.

Product Research


Overview: The Axxess AXDSPX-GM31 interface lets you add aftermarket amplifiers to the factory radio in select 2019-up Chevrolet and GMC vehicles without a factory amplifier. It features 10 individually assignable pre-amp outputs, each with independent 31 band graphic EQ, high-, low-, and band-pass filters, along with up to 10ms of delay time for each channel. The DSP interface retains all parking sensor chimes and OnStar voice prompts, with adjustable levels.

Compatibility: The AXDSPX-GM31 can be used with the following Chevrolet & GMC vehicles with factory non-amplified sound systems. Compatibility can be verified by accessing the vehicle's RPO (Regular Production Option) code list, usually located on the inside of the glove box.

Make Model Year RPO Code
Chevrolet Camaro 2019-up IOR
Cheyenne 2019-up IOR
Colorado 2019-up IOR
Cruze 2019-up -
Equinox 2019-up IOR
Malibu 2019-up IOR
Silverado 2019-up IOR
Sonic 2019-up -
Spark 2019-up IOR
Canyon 2019-up IOR
Sierra 1500 2019-up IOR
Terrain 2019-up IOR

Configuration: All configuration of the Axxess AXDSPX-GM31 is done through your connected Bluetooth enabled smartphone or tablet after downloading the AX-DSP-X mobile app, available at the Apple App (iOS 12.1 or higher) and Google Play stores. Configuration options can be saved, recalled, and reset to default from your device. A Password can be assigned to lock the interface from tampering. The Lock Down feature saves all selected settings, and must be done before closing the app or cycling the key, otherwise all setting changes will be reset to their default. Configuration options include:

  • Outputs: Allows you to select how many output channels will be used and their location in the vehicle. The first 5 Outputs are pre-assigned to L&R Front, L&R Rear, and Subwoofer, with Outputs 6-10 not used. These can be assigned and used for individual driver use, such as a mid-range or woofer speaker. Along with their Location labeling, Outputs can be grouped together, for simplified equalization. Each Output also features options for Invert, which reverses the phase, and Mute, for easier tuning of each individual channel.
  • Crossover: Each Output channel has its own Crossover, with options for High-Pass, Low-Pass, and Band-Pass. An intuitive virtual slide-bar lets you easily select the desired cutoff frequency while displaying it above the slide-bar. If Band-Pass is selected, two frequency sliders are displayed for the High- and Low-Pass settings, with both frequencies displayed above the slide-bar.
  • Equalizer: All Output channels can have a 31-band graphic equalizer applied to the signal. EQ bands range from 20Hz to 20kHz, with ±10dB of adjustment for each band.
  • Delay Adjust: The sound from each Output channel can be delayed, if desired. Output channel Delay is entered in inches with up to 99" of Delay available, based on the measured distance from each speaker to the driver's head-rest location.
  • Input/Levels: This Configuration screen provides the following:
    • Chime Volume: Warning tones can be adjusted for a balanced signal. Chime Volume range is 1-10, with indications for Low, Medium, and High.
    • Clipping Level: The AXDSPX-GM31 can detect clipping of the audio signals and reduce the level by 20dB for a period of time to prevent speaker damage. Option includes On/Off, and 1-10 adjustment scale.
    • Amp Turn-On: The connected amplifiers (sold separately) can be set to activate when Accessory power is turned on (Always On), or when a signal is detected from the radio (Signal Sense). A Turn-On Delay option can be set from 0-10 seconds.
    • Subwoofer Input: The Subwoofer Output can be driven from the sum of the Front and Rear inputs (Front + Rear), or directly from the Subwoofer input (Subwoofer), if provided by the factory system.

    Note: It is important to Lock Down all settings after performing any configuration changes. If not, closing the app or cycling the ignition key will reset all options back to factory default.

Bass Knob: A remote bass control is provided for individual adjustment of the Subwoofer output channel. The Bass Knob features 5' of bare-ended wire, for connection to the provided T-harness, and can be mounted under a dash edge using the provided mounting hardware.

Installation: Designed to integrate into select Chevrolet and GMC non-amplified factory sound systems, the AXDSPX-GM31 includes a wiring T-harness that plugs in between the factory radio and the factory radio harness. Additional T-harness connections plug into the included interface module, as well as provide the audio output RCA jacks, which include:

  • Outputs 1-4: These RCAs are color coded to match the "standard" wiring configuration;
    • White: Left Front
    • Gray: Right Front
    • Green: Left Rear
    • Purple: Right Rear
  • Outputs 6-10: These RCAs are assignable and are not color coded.
  • Subwoofer: A pair of Red/White RCAs provides the Subwoofer signal output.
  • Turn-On Output: A Blue/White Amp Turn-On wire can be used to activate connected amplifiers. This output can be assigned to activate with the ignition key or with radio signal sense, and can be delayed up to 10 seconds.


  • Input Channels: 6
  • Input Impedance: 1MΩ
  • Input Level: High or Low
  • Input Type: Differential Balanced
  • Input Voltage:
    • High-Level: 0-28V (peak-to-peak)
    • Low-Level: 0-4.9V (peak-to-peak)
  • Output Channels: 10
  • Output Voltage: Up to 5V RMS
  • Output Impedance: 50Ω
  • Equalizer Type: 31 Band Graphic, ±10dB
  • THD: <0.03%
  • Frequency Response: 20Hz-20kHz
  • Crossover: LPF, BPF, or HPF per channel
  • Crossover Type: Linkwitz-Riley 24dB/oct. slope
  • Sampling: 48kHz
  • S/N Ratio: 105dB @ 5V RMS
  • Operating Voltage: 10-16VDC
  • Operation Current Draw: 150mA
  • Standby Current Draw: 7mA

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Customer Q&A

4 questions already asked

Can you use this harness to install an aftermarket stereo ?
big d  Feb 28, 2024
1 answer
So this is designed to install an aftermarket amp while retaining your factory radio.
red  Feb 29, 2024 (Staff)
I have a 2020 Camaro (Non-Amplified) factory system. I installed the AX-DSP-XL-GM31 as instructed. Iâ??m only getting .17vdc from the remote out wire. Is there something I can do to circumvent this, outside of cutting the factory wiring?
rodney  Jul 30, 2023
1 answer
Greetings Rodney. Sorry you are having issues. If you purchased this adapter from Crutchfield we have free tech support for you. Our tech support number will be on shipping confirmation email. If you purchased this adapter elsewhere, you can always contact Metra (Axxess) support at 386-257-1187.
hogan  Jul 31, 2023 (Staff)
So I have a 2020 Silverado Work Truck RPO IOR. I verified already. My question is ... I read through the reviews on the other version the 30, and it says they had problems with the left speaker shutting off when the use the left blinker. Is this something that was fixed with this version (the 31). I will not spend this kind of money on a product that does not work as advertised. Will be running a 1000.5 and my old trusty Orion HCCA 225. Let me know because it does have some nice features I can use in my new truck. Thank you for your time. ?
richard  Sep 06, 2021
4 answers
Well first off your truck is either going to use the 30 or the 31. you have to scan the QR code on the driver side door and figure out what factory system you have. . But Factory your driver side speaker cuts out for your door chimes. The part works great i have used several different Axxess parts. Lets say you did not use this part and just high leveled your outputs to your amp then your door chime and Bluetooth phone calls would be so loud that you would probably jump out the window. Honestly for a $350 part it works great. It gives you an EQ Crossovers and Time Alignment. After you scan the QR code call if you see three letters that say IOS or IOT then it uses the GM30. If it has a code that says IOR then it uses the GM31. Hope this helps
stanley  Sep 10, 2021
i think this may be more of a deliberate design than a defect due to safety reasons. this is present with the 31 that i installed. it also cuts out with the seat belt chime. i agree its a little pricey but to retain the factory look and functions i like it. (21 trail boss) my hook up was behind the rt side kick panel, not behind the dash like the directions and you tube videos show though. talking to the manufacturer of the processor was very help full as they told me things that the instructions were vague on. help line was quick and easy.
robert  Sep 07, 2021
So, the unit has a feature that can lower the volume level of the door chimes, blinker, and other sounds made by the vehicle systems. All of the tones in newer GM vehicles are done threw the front left door speaker. So if you use that feature it will lower the volume of all audio coming out of the front left speaker including your music. There is not really a fix needed. If you just put the tone mute volume up all the way there is no issue. When any vehicle tone plays it will be at a normal volume like it was before you installed the unit and you music will not drop out. Also make sure the program lock down (saving your setup) finishes completely when your done programming or the unit can push feedback to your amp and fry it.
larry  Sep 06, 2021
It does shut off when you use your turn signals but comes right back on when it's off. I can tell you that using the axxess dsp compared to say the audio control lc2i is night and day. Axxess is way clearer and has way better options in the app to adjust everything. I have a 2021 silverado with 4 sundown SD-4 10s with an orion 2500.1dz. All sundown highs & mids on an orion 4 channel. Hope this helps. Also literally it's 2 plugs from the factory radio brains under your your glove box and your ready to go.
adam  Sep 06, 2021
What I would like to do is be able to control output to each set of factory installed speakers and install a sub and control it as well...for clarification will this do that? Will i need to install an amp for the sub? and can an it be powered through this processor?
anthony  Dec 24, 2020
1 answer
You will need to install an amp for the sub. The AX-DSP-X will provide sub outputs and remote wire for the amp. I ran 4awg wire to power Rockford Fosgate R2-750X1 with two JL Audio 10TW3-D4. It's 1Ohm stable and nice crisp low end sound.
christina  Dec 25, 2020

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