My check engine light is on

First, look at whether it's steady or flashing

This is the one thing that actually matters right now. A steady check engine light means the car has caught a problem and wants it looked at soon. A flashing or blinking light means the engine is misfiring badly enough that unburned fuel is going into the exhaust system, and it can cook the catalytic converter in a matter of minutes. If your light is flashing, get off the gas, pull over when safe, and don't keep driving on it. If it's steady, you can finish your errand and drive normally, but don't ignore it for weeks.

What usually causes it

Commonest first: a gas cap that isn't tight or has a worn seal. After that, a worn ignition coil or spark plug, an oxygen sensor going bad, or a vacuum hose with a small crack in it. Less common but more serious: a failing catalytic converter, or a sensor telling the engine computer the wrong information, which can make the car run rich or lean without you noticing at the pump for a while. A flashing light almost always means a misfire, which usually traces back to spark plugs, coils, or fuel delivery.

How to tell them apart before you bring it in

If the light came on right after you filled up with gas, check that the cap clicked shut. That alone fixes a surprising number of these. If the car is running rough, hesitating, or you can feel a stumble at idle or under acceleration, that points toward a misfire, spark, or fuel issue, especially if the light is flashing. A smell of rotten eggs from the exhaust often points toward the catalytic converter, sometimes caused by a misfire that's been going on a while. If the car drives completely normally and the light is just steady with no other symptoms, it's more likely something like an evaporative emissions leak or a sensor, which is lower urgency but still worth diagnosing.

What the repair involves and roughly what it costs

The only real way to know is to plug in a scan tool and read the stored codes, then check which ones actually explain what the car is doing, since more than one code can show up at once. That diagnostic step usually takes under an hour. From there, a gas cap or hose is a small, cheap fix. A coil or spark plug job is moderate, often in the low hundreds depending on how many cylinders are affected. An oxygen sensor is similar. A catalytic converter is the expensive end of this list, and if that's what it turns out to be, it's worth knowing that before agreeing to anything. We won't know which of these it is until the codes are pulled and checked against how the car is actually running, so it's not something we can price over the phone. If you're near Graham and want it looked at, we're open Saturdays too, which helps if weekdays are hard to get away.