Yes, a check engine light (CEL) can cause a vehicle to fail an emissions inspection. The check engine light indicates that the vehicle’s onboard diagnostic system has detected a problem with the engine, emissions system, or other critical components. Since the light signals potential issues that could affect emissions, most states require it to be off for a vehicle to pass an emissions or safety inspection.
Here’s what you need to know about how a check engine light can impact your inspection and what you can do about it.
Why Does a Check Engine Light Cause a Failure?
The check engine light turns on when the vehicle’s onboard diagnostics (OBD-II) system detects a malfunction. This system monitors components such as:
- The engine
- Emissions system
- Exhaust components (catalytic converter, oxygen sensors, etc.)
- Fuel system
Since the check engine light can indicate problems that impact the vehicle’s emissions, an illuminated CEL means your vehicle might be releasing more pollutants than it should. In most places, emissions regulations require that your vehicle is in compliance for it to pass inspection. If the light is on, the vehicle will fail the emissions test.
What Happens During an Emissions Inspection?
During an emissions inspection, a technician will typically:
- Connect an OBD-II scanner to the vehicle’s diagnostic port.
- Check for error codes: The scanner reads any stored trouble codes, including those that trigger the check engine light.
- Perform a tailpipe emissions test: In some cases, the technician will also check the actual emissions coming out of the exhaust.
If the check engine light is on, the technician will likely check the trouble codes and inspect the system. If the codes are related to emissions components, your vehicle will fail the inspection.
What Happens if Your Check Engine Light is On During Inspection?
If the check engine light is on during inspection:
- You will fail the emissions test (and possibly the overall inspection).
- The vehicle will not pass the inspection, and you may be required to fix the issue before returning for a re-test.
Can You Pass Inspection with the Check Engine Light On?
In most cases, no. However, there are some exceptions depending on the jurisdiction:
- In some states: You may be able to pass the inspection if the issue that triggered the check engine light has been resolved but the light is still on.
- If the issue was fixed but the light remains on due to a technical glitch or pending system reset, you may be allowed to pass after a certain number of drive cycles.
- In other states: If the light is on, the vehicle will fail the emissions test regardless of whether the issue has been fixed or not.
What Should You Do if Your Check Engine Light is On Before an Inspection?
1. Get a Diagnostic Scan
- Run a diagnostic scan using an OBD-II scanner to identify the trouble codes stored in the vehicle’s computer.
- Many auto parts stores offer free diagnostic scanning services that can help you identify what triggered the check engine light.
2. Address the Problem
- If the issue is something minor, like a loose gas cap, fixing it could turn the light off and make the vehicle ready for inspection.
- If the issue is more serious (e.g., a failing oxygen sensor, catalytic converter, or mass airflow sensor), you’ll need to repair or replace the faulty part before the light turns off.
3. Reset the Light After Repairs
- After fixing the problem, you may need to reset the check engine light. Some issues reset automatically after a few driving cycles, but you can also manually clear the code with an OBD-II scanner.
4. Check for Emission-Related Codes
- If the problem is related to the emissions system (e.g., oxygen sensor or catalytic converter), this will typically prevent your car from passing the emissions test. In this case, you may need to replace the faulty component.
Can You Pass Inspection If the Check Engine Light is Off But the Codes Are Still Present?
Even if the check engine light is off, stored trouble codes can still cause your vehicle to fail the emissions test. The technician will check for both active and stored codes during the inspection. If the codes indicate an unresolved issue with the engine or emissions system, the vehicle will fail the inspection.
Can You Clear the Check Engine Light to Pass Inspection?
While you may be able to reset the light temporarily using an OBD-II scanner, this is not a recommended solution. Resetting the light without fixing the underlying issue will not pass the inspection in the long term. If the problem persists and the light turns back on, your vehicle will still fail the inspection.
How Long Will It Take for the Check Engine Light to Reset After Repair?
Once the issue is fixed, the check engine light may turn off immediately, or it may take several drive cycles (usually 10-20) for the system to reset. A drive cycle refers to the process of starting the vehicle, driving it, and shutting it off, allowing the vehicle’s onboard computer to re-check the components and verify that the issue has been resolved.
Conclusion
A check engine light can cause your vehicle to fail an emissions inspection. If the light is on, the first step is to identify the underlying problem using a diagnostic scan. After repairing the issue, you can clear the codes and perform the necessary drive cycles to reset the light. Be sure to get the issue addressed before your inspection to avoid costly repairs and re-inspection fees.
FAQs
Can You Pass Emissions If the Check Engine Light is On?
In most cases, no. The check engine light needs to be off for your vehicle to pass the emissions inspection.
How Do You Reset a Check Engine Light?
You can reset it using an OBD-II scanner after fixing the underlying issue. Some issues reset automatically after a few driving cycles.
How Long Does It Take for the Check Engine Light to Reset After Repair?
Typically, it takes about 10-20 driving cycles for the system to reset. If the issue has been fixed, the light should turn off automatically.
Can You Clear Codes to Pass Inspection?
No, clearing the codes without fixing the issue will not pass the inspection. The technician will detect stored codes even if the light is off.
What Should I Do if My Check Engine Light Comes On Right Before Inspection?
Have the vehicle checked by a mechanic to identify and fix the problem before the inspection. Make sure the light is off and the issue is resolved.
Also Check:
• Does a Check Engine Light Turn Off by Itself?
• Does A Bad Catalytic Converter Affect Gas Mileage?
• Does A Bad Catalytic Converter Smell?
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