{"product_id":"metra-axxess-gmos-01-02-up-onstar-harness-adapter-retains-onstar","title":"Metra Axxess GMOS-01 02-Up Onstar Harness Adapter - Retains OnStar","description":"\u003cp\u003eIn this review the Metra Axxess GMOS-01 is evaluated as a practical harness adapter for installers working on non-amplified GM vehicles from 2002 onward. The bottom line: it keeps critical factory functions like \u003cstrong\u003eOnStar and dash chimes\u003c\/strong\u003e intact while providing adjustable output and accessory power, making it a straightforward choice when replacing a head unit in cars without factory amplifiers. Installers who need a pre-wired solution and USB update capability will appreciate the simplicity and focused feature set.\u003c\/p\u003e\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eOnStar retention:\u003c\/strong\u003e Retains OnStar functionality with adjustable volume output so voice prompts remain usable after head unit replacement.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eChime retention:\u003c\/strong\u003e Keeps the vehicle chime with its own adjustable volume output so warnings and reminders stay audible.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAccessory power:\u003c\/strong\u003e Supplies a fused 12-volt 10-amp accessory feed to power aftermarket radios reliably.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePre-wired convenience:\u003c\/strong\u003e Includes a pre-wired ASWC-1 harness interface connection for easier integration, reducing installation time.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUpdateable interface:\u003c\/strong\u003e USB update interface compatibility allows firmware updates without reworking the install.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAmplified vehicle guidance:\u003c\/strong\u003e Provides clear options for amplified systems via the GMOS-04 or an amp bypass procedure to avoid signal loss.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eWho It's For\u003c\/h2\u003e\n\u003cp\u003eThe GMOS-01 is aimed at mobile electronics installers and knowledgeable DIYers working on non-amplified GM vehicles who want to retain factory features after installing an aftermarket radio. It is especially useful where OnStar and audible chimes are required to remain functional and where a compact harness with accessory power is preferred.\u003c\/p\u003e\n\u003cp\u003eThose with amplified factory systems should look elsewhere or plan to use the GMOS-04 or follow the Axxess Interface Amp Bypass Schematic, since this unit is intended for non-amplified setups and requires additional steps for amplified vehicles.\u003c\/p\u003e\n\u003ch2\u003ePros \u0026amp; Cons\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003ePros\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eRetains both OnStar and dash chime with adjustable volume, preserving factory convenience and safety alerts.\u003c\/li\u003e\n\u003cli\u003eProvides a fused 12-volt 10-amp accessory output that simplifies powering an aftermarket head unit.\u003c\/li\u003e\n\u003cli\u003ePre-wired ASWC-1 harness compatibility and USB update interface make installation and future updates easier for professionals.\u003c\/li\u003e\n\u003cli\u003eClear guidance for amplified vehicles gives installers options rather than leaving them to guesswork.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eCons\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eNot a direct solution for amplified vehicles without the GMOS-04 or following an amp bypass procedure, which adds steps to some installs.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eSpecifications\u003c\/h2\u003e\n\u003ctable\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\u003c\/td\u003e\n\u003ctd\u003eMetra Axxess\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eModel\u003c\/td\u003e\n\u003ctd\u003eGMOS-01\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCompatibility\u003c\/td\u003e\n\u003ctd\u003eNon-amplified GM vehicles, 2002 and up\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAccessory Power\u003c\/td\u003e\n\u003ctd\u003e12-volt, 10-amp (fused)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFeatures\u003c\/td\u003e\n\u003ctd\u003eRetains OnStar, retains chime, retains RAP feature\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eUpdate Interface\u003c\/td\u003e\n\u003ctd\u003eUSB update compatible\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eIncluded Wiring\u003c\/td\u003e\n\u003ctd\u003ePre-wired ASWC-1 harness (ASWC-1 sold separately)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\u003ch2\u003eOur Verdict\u003c\/h2\u003e\n\u003cp\u003eThe Metra Axxess GMOS-01 is a focused, practical adapter for anyone replacing radios in non-amplified GM vehicles and who needs to keep factory OnStar and chimes functional. It offers useful installer conveniences like USB updates, a fused accessory feed, and pre-wired harness compatibility, delivering solid value for typical aftermarket radio installs. Choose the GMOS-04 or the amp bypass schematic only if your vehicle uses a factory amplifier.\u003c\/p\u003e\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eWill this work with a GM vehicle that has a factory amplifier?\u003c\/strong\u003e\u003cbr\u003eIf the vehicle is amplified, use the GMOS-04 interface or bypass the amplifier per the Axxess Interface Amp Bypass Schematic included in the documents.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it keep OnStar and the dash chime working?\u003c\/strong\u003e\u003cbr\u003eYes, the GMOS-01 retains both OnStar and the vehicle chime and offers adjustable volume outputs for each.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCan the interface be updated in the field?\u003c\/strong\u003e\u003cbr\u003eYes, it has a USB update interface for firmware updates without removing the unit from the install.\u003c\/p\u003e","brand":"Metra","offers":[{"title":"Default Title","offer_id":48199502364891,"sku":"B000K52DVY","price":67.95,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0724\/1043\/1707\/files\/511kE3EUemL.__AC_SX300_SY300_QL70_ML2.jpg?v=1770307201","url":"https:\/\/gearmusthave.com\/products\/metra-axxess-gmos-01-02-up-onstar-harness-adapter-retains-onstar","provider":"GearMustHave","version":"1.0","type":"link"}