Check Engine Light Disabling EyeSight And Cruise Control? Check Your Gas Cap.
If you're a Forester, Outback, or WRX owner and you've experienced a check engine light that kills your EyeSight, Lane Keep Assist, and cruise control systems, you're not alone.
Your first instinct was probably to panic - it’s natural to assume that your transmission is failing or that you’re looking at a massive repair bill. But before you call a tow truck or start draining your savings account, take a deep breath.
There's a high probability that your Subie is perfectly fine. A common cause of this startling domino effect on modern Subarus is actually one of the cheapest, simplest parts on the vehicle: a loose or cracked gas cap.
Here is exactly why a piece of plastic shuts down your advanced safety features, how to check it, and how to fix it for good.
The Domino Effect: Why Does EyeSight Shut Off?
It seems illogical at first. Why would a fuel system issue disable the cameras mounted up by your rearview mirror?
It all comes down to how Subaru’s Engine Control Unit (ECU) manages safety. Your vehicle is equipped with an Evaporative Emission Control System (EVAP). This system is designed to trap fuel vapors and route them back into the engine to be burned, rather than letting them escape into the atmosphere. To do this, the entire fuel system needs to be perfectly sealed and pressurized.
If your gas cap is loose, missing, or has a degraded rubber seal, the EVAP system detects a pressure leak and immediately triggers the Check Engine Light to alert you to the emissions failure.
Here is where the domino effect happens: Subaru’s engineers programmed the vehicle’s fail-safes so that whenever the Check Engine Light is triggered for any reason, the vehicle automatically disables EyeSight, Cruise Control, and traction control.
Because the computer has detected an engine or emissions fault, it essentially decides, "I can't guarantee the engine will respond perfectly if the crash-avoidance system needs to brake or accelerate suddenly." Out of an abundance of caution, it takes those advanced driver assistance systems offline until the engine code is cleared. Makes sense now, right?
Diagnosing the Cap
Before you head to the mechanic, check the cap yourself. Open your fuel door and give the cap a twist. Did it click? Subaru gas caps need to be tightened until they click at least once. If you left the gas station recently and forgot to tighten it down, you might have just found your culprit.
If the cap is tight, unscrew it and inspect the rubber O-ring gasket on the inside. Over time, heat, fuel vapors, and general wear and tear cause this rubber to dry out, flatten, or crack. If that gasket isn't perfectly supple and intact, it cannot hold the vacuum seal your Subaru demands.
The Importance of Using an OEM Replacement
If your cap is cracked or no longer sealing, you need a replacement. It’s tempting to run down to the local auto parts chain and grab a generic, cheap aftermarket universal gas cap off the shelf. Don't do it.
When it comes to the EVAP system on a modern Subaru, you should exclusively use Original Equipment Manufacturer (OEM) parts. Here is why:
- Exact Tolerances: The EVAP sensors on modern Subarus are notoriously sensitive. A generic gas cap is designed to 'sort of' fit a dozen different vehicle brands. An OEM Subaru gas cap is engineered with the exact thread pitch and depth required for your specific fuel filler neck.
- Proper Gasket Materials: The rubber compound used in a genuine OEM cap is formulated to withstand the exact pressures of a Subaru fuel system without prematurely shrinking or cracking. Cheap aftermarket caps often use inferior rubber that will trigger another Check Engine Light just a few months down the road.
- The Right Tether: OEM caps include the correct tether to easily pop right into your fuel door - you'll never lose the cap or have extra tether to wrap up and tuck away.
Using an aftermarket cap often results in a phantom Check Engine Light that comes and goes as the poor-quality seal fluctuates with outside temperatures. You will save yourself the headache by doing it right the first time.
OEM Parts from SubaruPartsPlus.com
If you’ve discovered your gas cap is the culprit, the fix is easy. Order a genuine OEM replacement cap matched to your VIN from SubaruPartsPlus.com.
Once you install the new, properly sealed cap, the Check Engine Light usually won't turn off instantly. The vehicle needs to run through a few drive cycles (starting, driving, and turning off the car) to run its internal diagnostics and confirm the leak is gone. After a few days of normal driving, the light should clear itself, and your EyeSight and Cruise Control will automatically come back online.
Don't let a dried-out piece of rubber keep your Subaru's best safety features sidelined. We're the e-commerce parts department of a family-owned Subaru dealership that has been in business since 2005. Our staffers are passionate Subaru enthusiasts with parts knowledge that is second to none. All OEM parts are backed by Subaru's manufacturer warranty. Check your cap, get in touch with our team if you have any questions, replace it with genuine OEM quality, and get back on the road safely!