How do you reset service engine light myself on 1999 Chevy Tahoe already found code put new plugs and wires Fuel filter went next Put gas in tank. Now is back on?

You can't simply reset the check engine light (CEL) on your 1999 Chevy Tahoe by a button press like some newer cars. The light comes on because the onboard diagnostic system (OBDII) has detected a problem. Since you've already replaced plugs, wires, and the fuel filter, and added gas, the light remaining on means the problem persists, or a new one has developed.

Here's what you should do:

1. Retrieve the Diagnostic Trouble Code (DTC): You mentioned you already found a code. Write it down! This is crucial. Even if you think you fixed the problem, the code tells you *what* the computer detected, not just that there was a problem. You likely used a code reader; if not, you'll need one. They're inexpensive and available at most auto parts stores.

2. Research the Code: Once you have the code (e.g., P0171, P0420, etc.), search online (e.g., Google the code plus "OBDII") to understand what it means. Websites and forums dedicated to car repair can be very helpful. Understanding the code will help you diagnose the root cause.

3. Address the Underlying Problem: Simply clearing the code won't fix the problem; the light will come back on. Focus on fixing whatever the code indicates. For example:

* Oxygen Sensor Issues (common): Codes related to oxygen sensors often indicate a faulty sensor needing replacement.

* Catalytic Converter Problems: These are expensive to replace, but sometimes a clogged converter can be the culprit.

* Mass Airflow Sensor (MAF) Issues: A dirty or faulty MAF sensor can cause poor fuel mixture and misfires.

* Other Sensors: Many other sensors can trigger the CEL.

4. Use a Code Reader to Clear the Code (AFTER Fixing the Problem): Once you've addressed the issue indicated by the code, *then* use your code reader to clear the code. The light should stay off if the repair was successful.

Important Considerations:

* Professional Help: If you're not comfortable diagnosing and repairing car issues yourself, take your Tahoe to a qualified mechanic. Improper repairs can lead to further damage and more expensive repairs later.

* Multiple Codes: Your vehicle might have multiple codes stored. Make sure your code reader can retrieve all of them.

* Intermittent Problems: Some problems might be intermittent, making them harder to diagnose. A mechanic might need to perform further tests to pinpoint the cause.

Don't just keep clearing the code – that's like ignoring a warning light on your dashboard. Fixing the underlying issue is vital for the proper functioning and longevity of your vehicle.