Customer Reviews

Axxess GMOS-04 Class II OnStar® Interface for Amplified Systems

5 star:		(4)
4 star:		(4)
3 star:		(0)
2 star:		(2)
1 star:		(4)

 

 

This product is worth every penny for the right installation (i.e. if you have amplified existing system - for me a Bose stock upgraded Chevrolet Silverado 2005 truck with OnStar). Trying to replace the stock system without this is difficult, even if you are ok with losing functionality of door chimes, RAP (delayed stereo powered on after turning ignition off), and OnStar (worth very little to me, as I don't pay for the service any more). It also displaces the need for a 24-pin wiring harness, so you save $15 there and the instructions work very well. The biggest thing is getting a cable that interfaces the preamp outputs to the amp inputs in the existing system. I was seriously looking at having to pull the stock amp and speaker routings out without this unit.

This devise does exactly what it was supposed to do. Made installing Pioneer AVIC-X920bt in my Hummer easy.

I've used these harnesses as well as the GMOS-01 harnesses over the years to today as I install radio's professionally. I've always ordered the GMOS-01 and GMOS-04 harnesses on here as where if you go to a retail store to purchase it. Cost is well over $100.

As for the other people's negative reviews on this product, claiming the harnesses are defective. More than likely it was human error to why they never worked for them. From as I've seen in the shop I use to work in and from what I see when I get called out to a customers house for a onsite repair. With the GMOS-04, people tend to automatically declare there harness being defective, for a couple reasons. One they incorrectly wire up there constant, accessory wires incorrectly and wont power on. Second (most common) problem to typically hear is that sound isnt being distributed to all speakers. As for the GMOS-04, obviously seeing you had 4 RCA hookups for your audio. Common do it yourself installer will have a headunit where they wont have the dual (front/rear) preouts on there headunit. If you go low grade or not careful you can buy headunits that only have Rear/Subwoofer Preouts (no front) and thats it. Obviously only getting half the audio and confusing the consumer and creating frustration thinking the harness is defective. As well there is audio adjusting screws for not just the door chimes but for the output for the audio and the screws are plastic and extremely fragile.

Best thing I recommend for this product is to take it to a professional installer.

First of all this is a necessity for installing a car stereo anymore. With all the various configurations in newer cars you don't want to go in and just start cutting plugs and wires. More specifically, with the Bose Lux models of GM trucks (mine is a 03 Denali, but I think Z71's and Denalis have this setup) it is required. The way the factory amps and head units talk on these vehicles, you need this adapter to wedge an aftermarket stereo into the equation. If you want to go fully aftermarket, you'll need to bypass the factory amps and subwoofer with new wiring, and install all new speakers.

That said, now that it's installed it works great. The gain knob on mine increases and decreases the stereo volume nicely, though the chime knob doesn't seem to change the volume of the "you left your keys in" chime at all. Maybe I'm listening for the wrong chimes.

Be aware that the instructions for this unit are very lacking. There are no photos or diagrams, and the directions are vague at best. I have installed a dozen or so stereos in my life, so I know a bit about what to do, but this was still slightly challenging. The biggest issue is actually that they have upgraded this harness over time (though there is no indication of WHICH GMOS-04 version you have received) and they have not updated the directions. So there are wires on the harness that are not mentioned in the directions.

Of particular note, I also bought a Metra Axxess ASWC Universal Steering Wheel Control Interface (Black) which is made by the same company. They were nice enough to actually do most of the wiring for that unit for you in the GMOS-04. In fact if you buy both you will only need the box from the steering wheel control- the plug (assuming you get a newer GMOS-04) is already integrated into the harness. You simply combine the ground wires and hot wires and then plug in the box. While this is convenient, the directions from both products made NO indication that the harness was there. The only way I figured it out was noticing the similarity of the extra plug, then tracing the wires according to the directions from the steering wheel control, and determining it was what I thought it was. Even then, I crossed my fingers on startup to see if it actually worked! (it did)

Also, the harness had a wire for "parking brake" and another for "reverse" though I had read online my truck did not have these available at the stereo connections. The parking brake may or not actually go to it, but with my stereo, a Pioneer AVH-P4300DVD 7" In-Dash Double-DIN DVD AV Receiver with iPod/iPhone Control, Pandora the parking brake needs to be on, off, then on again. So this was not possible with that wire. The reverse wire did in fact work, so the magic of the wiring harness comes through again.

As for the parking brake scenario, for that particular model (and probably other Pioneers, maybe other brands too), I was unable to access my parking brake sensor, so I installed a single pole single throw non-lighted switch on the wire, then ran that wire to ground. Mounted the switch on the dash, so now when I need video on the screen (only when parked of course; video while driving is really dangerous and very illegal) I just flip that switch on and off and it works. The system needs to see ground, but ONLY AFTER the unit is powered up. Simply running it to ground without the switch will not work.

I ordered this with an Alpine INA-W910 from a reputable online/catalog retailer that begins with a "C".

When I was ready to test out the system, I plugged the harness into my car and within a few minutes the GMOS-04 became VERY hot to the touch. In addition, the sound would not come through the speakers. I called tech support for where I purchased it and they said it sounded like a faulty unit. They quickly sent me another one and it worked perfectly.

If there are any other options, I would like to know, as the quality seems pretty poor; it is just a circuit board that rattles around in a chunky plastic case.

To all of those who complain about the chime noise, the nice feature is that you can totally turn off the volume.

Onstar interface works as expected. I replaced the stock stereo and installed the Pioneer 930 and was able to make the steering wheel controls and Onstar work together.

Door chimes and onstar work great, had to adjust the volume a few times, but sound good to me. Only thing is that car factory alarm is way more sensitive. Goes off for any door opening without hitting unlock button first, but not a problem at all.

I was very excited to finally get my new stereo installed when I get a call from the installer. He says the wiring harness is defective. After discussing it with him he says that this model breaks all the time, and is considering not accepting it in the future when a customer brings it in. Now I'm out even more time and money, do not buy.

After you wire it up, make sure to adjust the OnStar and Volume Gain Pots. After a little adjusting, the sound quality is great!

This makes your Onstar and other chimes sound like some toy. Which is very annoying. Seller refused to take it back, now I am stock with this junk.