Why Driving Your Vehicle Can Turn Off Your Check Engine Light

Was your vehicle just repaired, but the check engine light is still lit on the dashboard? Nancy explains how driving your vehicle can fix it!

Read the full video transcript

Why was my check engine light on when I just got my vehicle repaired?

Nothing is worse than being bugged by that pesky light, especially if you spend all that money to repair the issue and turn it off.

Hi, I’m Nancy at Kneble’s Auto Service Center.

I get your frustration.

What if I told you your car might not be broken and need another auto repair to turn out that light?

Before you curse out your auto technician, and I tell you why, pick a moment to relax about that light, and like us on Facebook, follow us on Instagram, and check out our YouTube channel.

Your check engine light is triggered when your powertrain control module, commonly referred to as a PCM, detects a problem.

Now, the PCM is like the brain of your vehicle. It monitors the functions of the engine and transmission, the two components of the powertrain.

Now that you have a basic understanding of how the light works, understand that the check engine light may still be on even after your vehicle has been repaired.

Spoiler alert, this is normal.

For the PCM to monitor the powertrain, the computer needs to see each system to detect no further problems.

This is where a drive cycle comes into play.

Well, just like repairing your laptop, all it usually takes is rebooting your computer.

Still, in this case, your PCM, or your car’s computer, monitors each component before getting a notification that it is operating correctly.

The drive cycle refers to driving your vehicle anywhere from 50 to 100 miles before the PCM can monitor each system and determine that the repair has fixed the problem, hence the check engine light going out.

Check out my other video, which explains the drive cycle in further detail.

Thank you for watching, and look for a video every Wednesday.

Call for your appointment at (609) 625-3286, or schedule it online through our website.

We are located here at 5473 Somers Point Road in Mays Landing, and you got it, of course, next to Freddy J’s Bar and Kitchen.

Thank you for watching.

Flashing vs. steady: one is urgent

Steady light? You have time. Could be a loose gas cap, could be an oxygen sensor, could be something else entirely. Schedule an appointment and get it looked at. No rush to pull over.

Flashing light is a different animal. That’s an active misfire happening right now, and every mile you drive is doing more damage. The catalytic converter is usually what takes the hit, and that’s one of the most expensive parts on the car. Pull over. Shut it off. Call for a tow.

Now, some of you went out and bought a code reader. And you scanned it. And you got a code like P0300. See, that code tells you there’s a misfire, but it doesn’t tell you why. Could be spark plugs. Could be fuel injectors. Could be a vacuum leak, a coil pack, half a dozen other things. The code points you in a direction. A technician figures out which one it actually is.

Buying a used car? Check the light first.

Turn the key and watch the dashboard. Every warning light should come on for a second or two, then go off. That’s the bulb test.

Two things to watch for. If the check engine light never comes on at all during that bulb test, somebody may have pulled it. They do that. If it comes on fine but the codes were recently cleared, the problems haven’t gone anywhere. They’ll come back after a few drive cycles. The seller just bought themselves a few days.

We do pre-purchase code scans for free. Ten minutes, we check for active codes, pending codes, and whether the monitors have finished running. You’re buying a car, you should know what you’re getting into.

If you need check engine light diagnostics, schedule an appointment or call us at 609-625-3286.