Things to Know About a Vehicle with the Check Engine Light On - Toyota Service Information To Know in Salem, OR

The Check Engine Light (CEL) is a warning that something has gone wrong with your car that will require a repair. However, despite its name, it may not always indicate an engine problem specifically. From tiny issues like a cracked or loose gas cap to show-stopping problems like a blown head gasket, a check engine light in your dashboard is not something to be ignored. But it doesn't always require a costly repair to fix.

When your car has a CEL, it's also storing even more information in the computer. When you visit our service center, our technicians will use this information to diagnose the underlying problem and carry out a fix.

Check Engine Light Symbol

6. Loose Gas Cap

Believe it or not, one of the most common causes of a sudden check engine light is a gas cap that simply wasn't tightened enough. Be sure to turn it until it clicks! The fuel system is both under pressure and designed to seal in all the harmful gasoline vapors. Even if the gas cap isn't quite sealed right, the engine computer can detect this and may turn on the check engine light. So check the fuel cap before getting too worried.

Wrenching On Engine

5. Suboptimal Air/Fuel Ratio

To achieve ideal performance, your engine has to burn the perfect ratio of air and fuel. The correct air/fuel ratio gives you the powerful response you expect and the best possible fuel efficiency. But, if there's a problem with the fuel delivery system, or the intake, the engine may not get the correct balance of air to fuel. This will lead to a reduction in power, a loss of fuel economy and, ultimately, a check engine light.

Possible causes of a bad air/fuel ratio include clogged engine air filters, a bad mass airflow sensor, bad O2 sensors, clogged fuel injectors and more.

4. Misfiring / Knocking / Rough Idle

Not only does the engine need the perfect ratio of fuel to air, it needs perfect timing to detonate the mixture at the ideal moment in the engine's cycle. If the spark isn't firing at the correct time, the engine may knock or run roughly. If the valves aren't in correct time with the pistons, the engine could misfire, which is when gasoline is burned outside of the engine itself, in the intake or exhaust. Problems like these are easily detected by the engine computer, which will trigger a CEL.

Potential causes of misfiring, knocking and poor running engines include worn out or fouled spark plugs, bad valve seals, improper engine timing and filling the tank with incorrect fuel, just to name a few.

OBD Scan Tool

3. Transmission Issues

Don't be fooled by its name -- the check engine light can indicate problems that develop on other components, too. If the transmission has suffered wear, needs service or just isn't running right, the check engine light may come on. If your engine seems to be running right, but the transmission shifts roughly, struggles to go into gear, comes out gear or the engine stalls when changing gears, that points to transmission trouble. If this is accompanied by a CEL, head to our service center right away so we can perform a repair before the damage gets worse.

2. Exhaust System Issues

The exhaust system is monitored by the engine, too. Sensors detect the presence of unburned gasoline in the exhaust to adjust the air/fuel ratio. If these sensors aren't working, the engine computer won't have enough information to maintain the air/fuel ratio and may alert you with a check engine light.

There's also a critical anti-pollution component on all modern cars called the catalytic converter. Without a working catalytic converter (or just "cat"), your vehicle would fail smog tests in jurisdictions where they are performed, pollute the atmosphere and also run poorly. Not to mention that removing or tampering with a catalytic converter can even be illegal! All modern cars should have a cat that works well. If your vehicle's catalytic converter isn't working as it should, the CEL will definitely come on.

1. Computer Issues

On modern cars, all the check engine lights are triggered by the engine's central computer. However, sometimes, the engine control module itself can malfunction. If all else fails, you may need to have the computer module replaced. Computer modules can suffer damage in an accident, or they can be damaged by shorts in the electrical system.

No matter what's gone wrong on your vehicle, we've got the expert service technicians and high-quality OEM Toyota parts to get your car back on the road and performing its best.