A lit check engine light fails an emissions test, and clearing the code right before the test does not work either. We find and fix the cause so the vehicle is ready to retest.

Call 817-709-1357 Text us Request a work order

Call hours: Mon to Fri 7:00 AM to 8:00 PM · Sat 9:00 AM to 4:00 PM

Check engine light in Southlake

Getting a vehicle with a lit light ready for an emissions test

An OBD emissions test plugs into the same port we use for diagnosis. If the check engine light is commanded on, the vehicle fails. The test also checks readiness monitors, the self-tests the computer runs on systems such as the catalytic converter, evap system and oxygen sensors. With too many monitors unfinished, the vehicle is rejected until they complete.

That second check catches the common shortcut of clearing codes right before the test. Clearing codes or disconnecting the battery resets every monitor to incomplete, and some take several days of normal driving to finish. The reliable path is to find what set the light, fix it, and then drive enough for the monitors to run. We can tell you which monitors are still incomplete before you go back.

Quick facts

Where

Your home, work or roadside in Southlake

Price

Given before any work starts

Call hours

Mon to Fri 7:00 AM to 8:00 PM · Sat 9:00 AM to 4:00 PM

Reach us

Call or text 817-709-1357

Warning signs

Common reasons a vehicle is not ready for testing

Light on from an evap leak

A loose cap, cracked hose or bad purge valve, often with no driving symptoms.

Catalytic converter efficiency code

Sometimes the converter, sometimes an oxygen sensor or an exhaust leak ahead of it.

Codes cleared recently

Monitors show incomplete until the car finishes enough normal drive cycles.

Battery recently replaced

The same reset happens, so the monitors need time to run again.

Oxygen sensor heater fault

A common cause of a lit light on an engine that otherwise runs smoothly.

How it works

From a failed test to a vehicle ready to retest

If the vehicle already failed, the test report is the most useful thing you can send. It lists the codes and any monitors that were not ready, which gives us a head start. Text a photo of it along with the year, make and model.

We come to the vehicle, read the codes and monitor status, and test the system involved instead of clearing the light. After the cause is confirmed, you get a price before any repair starts. Sensor, evap and vacuum repairs are usually done right there. Once the repair is finished, we explain which monitors still need to run and what kind of driving helps them complete. Converter replacements and other bigger jobs get scheduled.

Around Southlake

When to call before a test date

The best time to call is when you first notice the light, ideally a couple of weeks before the test is due. That leaves time for diagnosis, the repair, and the drive cycles the monitors need. If you already failed, keep the report handy. A steady light usually does not stop you from driving in the meantime, but a flashing one does, because it can damage the converter.

We cover all of Southlake

Your driveway, your work lot or the roadside, anywhere in Southlake. Call or text with the year, make and model and what the vehicle is doing.

Call 817-709-1357

Engine work in progress under the hood of a truck

Why Day's

Shop-level work, where you park.

We bring dealer-level diagnostic tools, including a lab scope and a thermal camera, to wherever your vehicle is parked.

Fords are our specialty, built on years of maintaining a construction company's fleet, from cars and light trucks to heavy-duty work trucks.

About Day's

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Questions

Check engine light questions from Southlake.

Will clearing the code let me pass the emissions test?

Usually not. Clearing codes resets the readiness monitors, and the test checks those as well. If too many are incomplete, the vehicle is rejected, and the fault will set the light again once the computer retests it. Text us to have the cause found and fixed instead.

How long after a repair can I go back for the test?

It depends on which monitors need to complete. Some finish in a single drive, while the evap monitor can take several days of normal use. We can check monitor status before you go back. Call or text if you want us to confirm the vehicle is ready.

Can you help if my car failed its emissions test in Southlake?

Yes. We come to the vehicle, read the codes and monitor status, and test the system that caused the failure. You get a price before any repair. Request a work order and describe what the test report says, or have it ready when we arrive.

Can a gas cap make me fail an emissions test?

It can set an evaporative leak code that turns on the check engine light, and a lit light fails the OBD test. Tighten the cap until it clicks and drive normally for a few days. If the light stays on, the leak may be a hose or valve, so call or text us.