1. Check Engine Light (CEL) and Built-in Diagnostics (OBD I):
* The Blink Code Method (most likely for a 1999 Chevy): 1999 Chevrolets likely use a system where the Check Engine Light (CEL) flashes a specific code. This is often a two-digit code represented by a series of long and short flashes. You'll need to:
* Locate the Diagnostic Connector: This is usually under the dashboard, near the steering column. It might be a two-prong connector or a more elaborate one.
* Short the Connector: Use a paperclip (carefully!) or a jumper wire to connect the appropriate two terminals in the connector. The specific terminals vary by vehicle; consulting your owner's manual is crucial. Some models might need a specific "test" mode activated before attempting this.
* Observe the CEL: The CEL will flash a series of long and short flashes representing the trouble code. Write down the sequence of flashes.
* Decode the Code: You'll need a 1999 Chevy-specific blink code chart to translate the flashes into trouble codes. These charts are sometimes available online (search for "[your Chevy model] 1999 blink codes") but are not always easy to find and can vary based on the specific PCM (Powertrain Control Module) in your car. Your owner's manual *might* have some limited information, but it's not always comprehensive for this method.
2. Using an OBD-I Scanner:
* OBD-I Scanner: Since a 1999 Chevy uses OBD-I, you'll need a scanner designed for this older standard. Many modern OBD-II scanners won't work. A dedicated OBD-I scanner or an adapter that allows OBD-II scanners to read OBD-I data is required. These can be found online or at some auto parts stores. The scanner will plug into the diagnostic connector and directly display the trouble codes.
3. Professional Diagnostics:
* Auto Parts Store: Most auto parts stores offer free OBD-I or OBD-II code reading services. However, they might struggle with a 1999 vehicle if they mainly focus on newer cars. Call beforehand to check.
* Mechanic: A qualified mechanic will have the necessary tools and expertise to read and interpret the trouble codes from your 1999 Chevy. This is often the most reliable method, especially if you're unsure about the other techniques.
Important Considerations:
* Owner's Manual: Your owner's manual is your best friend. It should contain information about locating the diagnostic connector and any specific instructions for accessing trouble codes.
* Year and Model: The exact method and availability of information will depend on the specific make and model of your 1999 Chevy. Be as precise as possible when searching online for information.
* Safety: Always disconnect the jumper wire or paperclip from the diagnostic connector before turning the ignition off.
If you're uncomfortable working with car electronics, taking it to a mechanic is the safest and most reliable option. The blink code method can be tricky, and incorrect connections could damage your car's electrical system.
