A check engine light can come on for many different reasons. Some problems are minor, while others can affect fuel economy, emissions, drivability or engine performance.
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Kool2U Auto Repair Service provides check engine light diagnosis for cars, trucks, SUVs, vans and many light duty work vehicles.
Service is performed by experienced technicians under the direction of an ASE Master Technician.
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Common Questions About Check Engine Lights
What causes a check engine light to come on?
A check engine light can be triggered by problems involving the engine, fuel system, ignition system, emissions system, sensors, wiring or electronic controls.
Common causes can include:
• Faulty oxygen sensors
• Misfires
• Evaporative emissions leaks
• Fuel system problems
• Ignition coil problems
• Spark plug problems
• Mass airflow sensor problems
• Catalytic converter problems
• Wiring faults
• Sensor failures
• Vacuum leaks
• Computer or module related faults
Reading the trouble code is only the first step. Additional testing may be needed to determine what actually caused the code.
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Is it safe to drive with the check engine light on?
Sometimes, but it depends on the cause.
If the vehicle is running normally and the light is steady, the problem may not require immediate shutdown, but it should still be diagnosed.
If the light is flashing, the engine is running poorly, the vehicle is losing power or you notice unusual noises, smoke or strong odors, the vehicle should be inspected promptly.
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What does a flashing check engine light mean?
A flashing check engine light often indicates a more serious problem, such as an active engine misfire.
Continuing to drive with a severe misfire can damage the catalytic converter and may lead to additional engine or emissions system problems.
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Can a loose gas cap cause the check engine light to come on?
Yes. A loose, damaged or improperly sealed fuel cap can cause an evaporative emissions system leak and trigger the check engine light on some vehicles. If the gas cap was recently removed, make sure it is properly tightened. If the light stays on, additional diagnosis may be needed.
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Will the check engine light turn off by itself?
Sometimes. If the problem was temporary and does not return, the vehicle computer may eventually turn the light off after several successful drive cycles. If the underlying problem is still present, the light will usually remain on or return.
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Can a bad oxygen sensor cause a check engine light?
Yes. Oxygen sensors help the vehicle computer monitor exhaust gases and adjust fuel delivery.
A failing oxygen sensor can trigger a check engine light and may contribute to poor fuel economy, emissions problems or drivability concerns.
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Can bad spark plugs cause the check engine light to come on?
Yes. Worn or damaged spark plugs can cause engine misfires, rough running, poor acceleration and reduced fuel economy.
Misfires can also be caused by ignition coils, fuel injectors, wiring, compression problems or other engine faults.
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Can a bad ignition coil cause a check engine light?
Yes. A failing ignition coil can cause one or more cylinders to misfire.
Symptoms may include rough idle, hesitation, poor acceleration, reduced fuel economy and a flashing or steady check engine light.
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Can a vacuum leak cause the check engine light to come on?
Yes. A vacuum or intake air leak can allow unmetered air into the engine and affect the air and fuel mixture.
This can cause lean condition codes, rough idle, hesitation or other drivability problems.
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Can a fuel system problem trigger the check engine light?
Yes. Fuel pressure problems, failing injectors, fuel delivery issues and mixture problems can all trigger diagnostic trouble codes.
Proper testing may be needed to determine whether the problem is mechanical, electrical or related to a sensor.
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Does a check engine light always mean there is an emissions problem?
No. The check engine light is part of the vehicle’s onboard diagnostic system and can indicate problems involving emissions, ignition, fuel delivery, engine performance, sensors or electronic controls.
Some faults affect emissions directly, while others affect the way the engine runs.
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What is the difference between reading a code and diagnosing the problem?
A trouble code tells you which system or condition the computer detected.
It does not always identify the failed part.
For example, an oxygen sensor code may be caused by the sensor itself, wiring, an exhaust leak, fuel mixture problem or another engine issue. Proper diagnosis uses the code as a starting point and then tests the system to determine the cause.
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Can low battery voltage cause a check engine light?
Yes. Low battery or charging system voltage can sometimes cause communication faults, sensor codes or unusual electronic behavior.
Battery and charging system testing may be needed when several warning lights appear at the same time.
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Why did my check engine light come on after a repair?
A check engine light after a repair does not always mean the repair caused the problem.
The vehicle may have developed a separate fault, a connector may have been disturbed or the computer may have detected a condition that was not present before.
The trouble codes should be read and diagnosed rather than assuming the cause.
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Can Kool2U diagnose a check engine light at my home or workplace?
Mobile diagnosis may be available depending on your location, vehicle and the type of testing required.
Some check engine light problems can be evaluated at the vehicle’s location, while more complex testing may require the vehicle to be brought to our San Antonio repair facility.
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When should I take my vehicle to the shop for a check engine light?
Shop diagnosis may be more appropriate when the problem requires advanced electrical testing, fuel system testing, smoke testing, emissions diagnosis, extensive wiring inspection or other equipment that is better suited for a repair facility.
Kool2U can help determine whether mobile service or shop service is the better option.
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Need Help With a Check Engine Light?
Kool2U Auto Repair Service can diagnose check engine lights, misfires, fuel system problems, ignition problems, sensor faults, emissions concerns and related electrical issues.
Kool2U Auto Repair Service
4531 N. Stahl Park Suite 111
San Antonio, TX 78217