How to Replace a Factory Stereo Without Losing Features

Keep your sound quality and the features

Throughout the long history of car audio, the process of upgrading a factory head unit has been standard practice for those who demand greater sound quality, power, and features. It was often the case that the manufacturer-installed OEM car stereos were feature-poor, and there weren't many downsides to replacing it with an aftermarket head unit.

The landscape of aftermarket and OEM car stereos is more complicated today, and many owners of late-model vehicles asking themselves the question of whether losing OEM features is worth the trade-off of getting better sound quality from an aftermarket head unit. With the rise of infotainment systems, integration with steering wheel controls and voice controls, and OEM telematics systems like OnStar, simply popping out a factory head unit and installing a powerful new aftermarket one actually can impact or disable a lot of great features.

However, with some careful planning, the right adapters, and accessories, it’s possible to upgrade a modern factory head unit without losing anything.

complicated infotainment controls
Some infotainment systems are difficult to operate without taking your eyes off the road, but they may have useful features you don't want to lose. Jupiterimages / Stockbyte / Getty

Keeping the Features You Want

Infotainment is a portmanteau of the words information and entertainment that means slightly different things depending on the OEM in question. It’s an umbrella term that gathers in everything from GPS navigation to Bluetooth integration and in-car multimedia, and a growing percentage of new cars sold each year come with these systems instead of basic head units.

Depending on the specific features that your vehicle’s head unit or infotainment system came with, you may want to retain some, while you may be willing to let go of others. It’s important to take this into consideration when looking at upgrade options.

Features that you may lose access to by switching to an aftermarket head unit include, but are not limited to:

  • Steering wheel audio controls
  • Voice controls
  • Factory Bluetooth integration
  • Satellite radio
  • Factory amplifiers
  • OEM telematics (i.e. OnStar, Sync, etc)
  • USB media players
  • Rear seat entertainment systems
  • Safety alerts
  • Navigation

Aftermarket Head Units, Wiring Harnesses, and Adapters

Three primary factors affect which features you’ll have access to when you upgrade a factory car stereo with an aftermarket unit. The specific head unit you pick is probably the biggest factor since, in order to keep many features, you have to choose a head unit that has those features and is compatible with the requisite harness or adapter. For example, if you replace a factory navigation head unit with an aftermarket unit that doesn’t include that feature, you’ll lose it.

Retaining some other features can be a little more complicated, and you will often have to work backward: identify the features you want to keep, find an appropriate adapter unit, and then look for an aftermarket head unit that works with that adapter and that has all the other features and specifications you want.

Wiring harnesses are really at the root of any head unit upgrade, and there are a few different ways that they can come into play. Some car stereo wiring harness adapters are designed to connect an aftermarket head unit to a vehicle’s wiring harness without any cutting, splicing, or soldering. Other harness adapters are designed to be wired to the harness that came with your new head unit, after which they can be plugged directly into the vehicle wiring harness connector.

Beyond those basics, wiring harness adapters can also be used for specialized functions like connecting to or bypassing a factory amplifier. So, if your car actually came with a decent amp that you’d like to keep using, you can do so by acquiring a wiring harness adapter that’s designed to connect that specific factory amp to an aftermarket head unit.

On the other hand, if you want to bypass an anemic factory amp and use the built-in amp included in your new head unit, or even upgrade to a brand new external amplifier, there are harnesses designed for that purpose.

Keeping Steering Wheel Audio Controls

Steering wheel audio controls are probably one of the most basic features that you may want to hang on to when you upgrade your factory head unit, and there are a few different ways to go about it. This is also one of the easiest features to integrate with a new head unit, and a huge variety of aftermarket car stereos include some type of steering wheel audio control compatibility.

In order to retain steering wheel audio control functionality, you need two things: a compatible head unit and an adapter. The first part is relatively easy due to the prevalence of this feature in cars. When looking at potential new head units, you’ll just want to keep an eye out for ones that list either “wired remote control input” or “SWI” (steering wheel input) as a feature.

After you identify a compatible head unit that includes all the other features you’re interested in, you’ll have to buy an appropriate steering wheel audio control adapter. For instance, if the head unit is SWI-JS compatible, which stands for Jensen and Sony, then you’ll have to find an SWI-JS adapter that’s designed to work with your make and model of vehicle.

Other OEM Features

In order to retain access to features like factory Bluetooth integration and OEM telematics, like OnStar and Sync, you need a much more complex adapter than one for the steering wheel audio controls, and many of them actually include the ability to retain SWI functionality. With the correct interface module, it may be possible to retain access to features like:

  • Steering wheel controls
  • OEM telematics
  • Digital amplifier controls
  • Factory Bluetooth integration
  • Navigation outputs
  • Satellite radio

These interface modules are essentially designed to be plugged into the original factory harness and then connected to a compatible aftermarket head unit. In some cases, you may need to cut and splice some wires to complete the installation, and in others, it is simply a matter of plugging in the necessary harness adapters. In any case, the features that you retain access to will depend on factors like the make, model, and year of your vehicle and the capabilities of the aftermarket head unit that you choose.

For instance, if your OEM head unit included built-in satellite radio, then an interface module won’t allow you to retain access to satellite radio functionality. If the OEM head unit was only "satellite radio," and came with an external satellite radio module, then an interface module will probably allow you to integrate it with your new head unit, provided that you select a compatible aftermarket head unit and that the right interface module exists in the first place.

Other Concerns When Upgrading Factory Head Units

The problem of fit and finish can represent almost as large a hurdle as the potential for lost features when replacing a factory head unit. Aftermarket head units typically conform to the single DIN and double DIN form factors, while the OEMs have increasingly moved toward nonstandard head units in recent years.

In some cases, you may be able to find an aftermarket head unit that includes the features you want and that is specifically designed to replace your non-standard factory head unit. This isn’t terribly common, and the options are inherently more limited, so the chances are pretty good that you’ll be out of luck if you really have your heart set on a direct-fit replacement for your nonstandard factory head unit.

When a direct-fit replacement isn’t available, then you can either locate an appropriate stereo install dash kit or have one fabricated. The former is less expensive, and dash kits are available for most new vehicles that include nonstandard modular head units. They can be somewhat complicated to install, depending on how integrated the factory head unit controls are with the dash, but you will typically end up with a relatively clean-looking installation.

Fabrication is more complicated and typically more expensive, but it is an option when a dash kit isn’t available. Some DIYers opt to fabricate their own dash kits, but it definitely isn’t a project for the faint of heart, especially if you are worried about the look of your new vehicle. Skilled DIY mods and professionally fabricated dashes can look incredibly good, though, and in some cases, the end result is even more aesthetically pleasing than a generic dash kit.

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