ACM (Audio Control Module)

Modules

The radio/head-unit module in GM HMI-based infotainment systems containing the AM/FM/HD/SiriusXM tuner and base amplification.

The Audio Control Module (ACM) is the radio in GM HMI-based infotainment systems — separate from the HMI module and separate from the touchscreen. It contains the AM/FM/HD Radio/SiriusXM tuner and either drives the speakers directly (base audio configurations) or hands audio data off over MOST bus to an external amplifier (Bose/premium audio configurations).

On IO5 and IO6 vehicles (2014–2019 era), the ACM is a discrete module that can be replaced or upgraded independently of the HMI. The radio must match the vehicle’s audio configuration:

  • Vehicles with RPO codes UQ3, UQ5, UQF (Base audio) use a base ACM.
  • Vehicles with UQG (Enhanced Audio with Amplifier) use an ACM matched to the amplifier.
  • Vehicles with UQA, UQS, UQH (Premium/Bose) use a Bose-spec ACM that outputs audio data over MOST to the Bose amplifier.

You cannot mix and match Bose and base ACMs — installing a base ACM in a Bose-equipped vehicle (or vice versa) results in no audio. GM also refers to the ACM as the “Silverbox” on some platforms.

On CSM-based vehicles (2017.5+ Cadillac, 2018.5+ other brands), there is no separate ACM — the tuner and audio routing are integrated into the CSM itself.

A failed ACM typically presents as no audio (with the HMI otherwise working), missing HD Radio, missing SiriusXM, or “LOCKED”/”THEFTLOCK” if the VIN authority handshake fails.

Vehicle Applicability

2014–2019 GM HMI-based vehicles with IO5 or IO6 RPO codes. Not used on CSM-based vehicles (the CSM contains the tuner internally).

Also known as: Radio, Head Unit, Silverbox

Related Terms

  • HMI — The primary infotainment computer in most 2013–2020 GM vehicles with MyLink, IntelliLink, or first-generation CUE.
  • CSM — GM's unified next-generation infotainment computer that replaced the HMI starting on select GM platforms in mid-2017.5.
  • BCM — The central body-electronics computer in a GM vehicle. Owns lights, locks, windows, anti-theft authority, and the VIN authority other modules authenticate against.
  • IO5 — The GM RPO code for the non-navigation HMI 2.0/2.5 infotainment configuration found on most 2014–2019 GM vehicles.
  • IO6 — The GM RPO code for the HMI infotainment configuration with embedded factory navigation, found on premium-trim 2014–2019 GM vehicles.
  • MOST bus — The high-speed multimedia network that connects HMI, radio, and amplifier on GM HMI-based vehicles. GM's implementation uses copper conductors in a ring topology.
  • GM Audio RPO Codes — Reference table of GM audio system RPO codes — UQ3, UQ5, UQF, UQG, UQA, UQS, UQH — used to identify whether a vehicle has base audio, mid-tier enhanced audio, or Bose premium audio.
  • Theft Lock — The anti-theft state a GM radio or module enters when its stored VIN doesn't match the vehicle's VIN. Renders the unit non-functional until properly reprogrammed.

Learn More

Shop Related