How do you reset the service engine soon light on a 99 silverado?

The "Service Engine Soon" light (SES light) on a 1999 Silverado doesn't simply reset with a button press like some newer cars. It indicates a problem detected by the onboard diagnostic system (OBDII). You must address the underlying issue causing the light to come on before resetting it. Ignoring the light can lead to further damage.

Here's the process:

1. Diagnose the Problem: The first and most crucial step is to find out *why* the light is on. You have a couple of options:

* OBDII Scanner: The most effective way is to use an OBDII code reader. These are inexpensive and widely available at auto parts stores. Plug it into the OBDII port (usually under the dashboard) and it will retrieve diagnostic trouble codes (DTCs). These codes will give you a clue about the problem. Look up the codes online (many free resources are available) to understand their meaning.

* Mechanic: If you're uncomfortable diagnosing the problem yourself, take your truck to a qualified mechanic. They'll have the tools and expertise to pinpoint the issue.

2. Repair the Problem: Once you know the cause of the SES light, fix the problem. This could be anything from a loose gas cap (a common cause) to a more serious issue like a sensor malfunction or emissions system problem.

3. Clear the Code (After Repair): After you've repaired the issue, you can clear the code. There are several ways to do this:

* OBDII Scanner: Most OBDII scanners have a function to clear codes. Simply connect the scanner, and choose the "clear codes" option.

* Disconnect the Battery: A less precise method is to disconnect the negative (-) battery terminal for about 10-15 minutes. Reconnect the battery, and start the truck. This *may* clear the code, but it doesn't guarantee it. It's also important to note this method won't work on all OBDII systems and won't tell you the root cause of the initial problem.

Important Considerations:

* The light will return if the problem isn't fixed. Resetting the light without addressing the underlying issue is a temporary fix and could mask a serious problem that could damage your engine or cause safety issues.

* Safety First: If you're not comfortable working on your vehicle, it's always best to take it to a professional mechanic.

In short: Don't just reset the light. Fix the problem that caused it. Then, and only then, reset the code using an OBDII scanner for the most reliable results.