How to Pass Inspection & Complete a Drive Cycle
If you've recently cleared your check engine light, there's one important thing you should know before heading to your next vehicle inspection: clearing the light doesn't automatically mean your car is ready to pass.
This is a follow-up to my video, How to Read & Clear a Check Engine Light. I'll explain what a drive cycle is, why it matters, and how to check whether your vehicle's onboard diagnostics are ready for inspection.
First, a Quick Disclaimer
I'm not a mechanic, so I recommend having your vehicle checked by a trusted professional. I take my car to Bobby's Auto on Route 1A in Walpole, Massachusetts. He's a good guy—tell him BigNate sent you!
Why Clearing the Check Engine Light Isn't Enough
In my previous video, I may have given the impression that clearing the check engine light was all you needed to do to pass inspection. That's only part of the story, and I don't want to lead anyone astray.
When you clear a trouble code, you can also reset the vehicle's readiness monitors. These monitors are part of the onboard diagnostic system and check whether various emissions-related systems are operating as expected.
If you head straight to inspection before the required monitors have completed their tests, your vehicle may be rejected—even if the check engine light is no longer illuminated.
The good news? A rejection for incomplete readiness monitors doesn't necessarily mean something is broken. It may simply mean your car needs more driving before its diagnostic tests can finish.
What Is a Drive Cycle?
A drive cycle is a series of driving conditions that allows your vehicle's engine control module (ECM) to run its diagnostic tests.
Depending on your vehicle, the process may involve:
Starting the engine after it has cooled down.
Allowing the engine to warm up.
Accelerating and decelerating under certain conditions.
Driving at regular road speeds.
Cruising at highway speeds for a period of time.
The exact procedure varies by make, model, year, and operating conditions. Check your owner's manual or consult a qualified mechanic for the correct drive-cycle procedure for your vehicle.
Don't assume that one quick trip around the block will do the trick!
How Do You Know When You've Completed a Drive Cycle?
Here's where my little diagnostic tool comes in handy.
You can read the vehicle's diagnostic information again and look under Monitors or Readiness. This screen shows which diagnostic monitors have completed their tests and which are still incomplete.
In my example, the goal was to see 0 incomplete monitors and 8 ready monitors.
If the screen instead showed 2 incomplete and 6 ready, I'd know that two monitors hadn't finished their tests yet.
Keep in mind that your vehicle may have a different number of supported monitors, and inspection requirements can vary. The important thing is to check the readiness status against the requirements that apply to your vehicle.
Once the required monitors are ready, you can head back for your inspection—assuming you've also addressed any underlying problems that caused the check engine light in the first place.
One final reminder: Clearing a trouble code doesn't repair the problem that triggered it. If the light came on because something needs attention, get the cause diagnosed and repaired rather than simply trying to get the light to disappear.
Thanks for watching, and I'll see you in the next video.
— BigNate84
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