Your Check Engine Light Is Trying To Warn You
You’re driving down the highway, and everything feels fine. Then, out of nowhere, that little orange light flickers on. You stare at it, hoping it disappears. It won’t. You check the engine temperature, listen for weird noises—nothing seems off. But that light isn’t lying. Your car is trying to warn you.
At Cowden Automotive in San Francisco, we’ve seen too many drivers from Daly City wait too long to get it checked. The result? A minor issue turns into a costly, avoidable repair. If your check engine light is on, it’s time to find out why. Here are the five most common reasons—and what needs to be done before it’s too late.
1. Oxygen Sensor Failure: The Fuel Economy Killer
Your oxygen sensor keeps your engine running efficiently by monitoring the fuel-to-air ratio in the exhaust. When it fails, your car burns more gas than necessary, emissions skyrocket, and your engine’s performance declines. Left unchecked, it can damage your catalytic converter, leading to a repair you don’t want to pay for.
This issue is common in Honda Accords (2003-2012), Ford F-150s (2004-2013), and Nissan Altimas (2005-2014), especially after 80,000 miles. If your car feels sluggish or your fuel efficiency has dropped, a faulty oxygen sensor could be the culprit.
What To Do: A diagnostic test at Cowden Automotive will confirm if your oxygen sensor is failing. Replacing it early will save you from worse problems down the road.
2. Catalytic Converter Failure: The Rotten Egg Warning
Your catalytic converter is the unsung hero of your exhaust system, breaking down harmful emissions before they leave your tailpipe. When it fails, your engine struggles, your fuel economy plummets, and your car starts releasing an unmistakable rotten egg smell.
This issue often strikes Toyota RAV4s (2006-2018), Chevy Equinoxes (2010-2017), and Subaru Foresters (2009-2015). Many failures happen because of neglected maintenance—like ignoring a bad oxygen sensor or skipping oil changes.
What To Do: If your check engine light is on and your car smells bad, don’t ignore it. A failing catalytic converter won’t fix itself. The sooner you address it, the less damage it causes.
3. Mass Air Flow Sensor Failure: Your Engine Can’t Breathe
Your car’s mass airflow (MAF) sensor measures how much air is coming into the engine. If it fails, your engine struggles to get the right fuel mixture, causing hesitation, rough idling, or even stalling.
This issue is common in BMW 3 Series (2007-2015), Ford Mustangs (2005-2014), and Chevy Tahoes (2004-2013). Often, a dirty or clogged air filter is the root cause, leading to unnecessary wear on the MAF sensor.
What To Do: Replacing the air filter on schedule can prevent this problem. If your engine is running rough, get the MAF sensor checked before it causes long-term damage.
4. Misfiring Spark Plugs: The Rough Ride You Can’t Ignore
Spark plugs ignite the fuel in your engine, and when they fail, the entire system suffers. You might notice rough idling, loss of power, or even difficulty starting your car. Worse, misfires can damage the catalytic converter, turning a cheap repair into a costly one.
This is a frequent problem in Toyota Corollas (2009-2018), Honda CR-Vs (2005-2015), and Dodge Chargers (2011-2020), especially in high-mileage vehicles that haven’t had regular tune-ups.
What To Do: If your engine feels rough or struggles to accelerate, don’t wait. Replacing spark plugs on time prevents misfires and protects other engine components.
5. Loose Or Faulty Gas Cap: The Simplest Fix You’ll Ever Make
Believe it or not, a loose or damaged gas cap can trigger your check engine light. Modern fuel systems require a sealed environment, and if fumes escape, your car’s computer flags it as a leak.
This issue can happen to any vehicle, but it’s especially common in Jeep Grand Cherokees (1999-2010), Ford Escapes (2008-2016), and Honda Civics (2001-2011). Over time, the rubber seal on the gas cap wears out, causing small leaks.
What To Do: Before you panic, check the gas cap. If it’s loose, tighten it. If it’s cracked or worn, replace it. It’s the cheapest fix for a check engine light you’ll ever make.
Ignoring That Light Could Cost You Thousands
What starts as a small sensor failure today could turn into a major engine issue tomorrow. At Cowden Automotive in San Francisco, we help Daly City drivers diagnose and repair check engine light problems before they get worse.
If your check engine light is on, don’t wait until your car breaks down. Call Cowden Automotive at (415) 777-9858 today and get it checked before it’s too late.