1. Using an OBD-II Scanner:
This is the easiest and most reliable method. OBD-II (On-Board Diagnostics II) scanners are relatively inexpensive and readily available at auto parts stores like AutoZone, Advance Auto Parts, or online retailers.
* Obtain a scanner: Make sure the scanner is compatible with OBD-II, which your Trailblazer uses. Many scanners offer a range of features, from simply reading codes to displaying live data and even offering diagnostic suggestions.
* Locate the OBD-II port: This is usually located under the dashboard, often near the steering column. It's a 16-pin connector.
* Connect the scanner: Plug the scanner into the OBD-II port.
* Turn the ignition on: Turn the key to the "ON" position (without starting the engine).
* Read the codes: Follow the instructions on your specific scanner to retrieve the Diagnostic Trouble Codes (DTCs). The codes will be a series of letters and numbers (e.g., P0171).
* Look up the codes: Use the codes you obtained to look up their meaning in a repair manual, online database (like a Haynes manual or online forums), or even using the scanner's built-in code lookup feature. This will tell you what problem the car's computer has detected.
2. Using the Key-On/Key-Off Method (Check Engine Light Flash Codes):
This method is less common now with the prevalence of OBD-II scanners, and it's not always reliable. However, it *might* work on your Trailblazer. This involves manually checking the blinking pattern of your check engine light. This method is very car-specific and its reliability depends on the vehicle’s system. It is usually less reliable than using a scanner.
* Locate the diagnostic connector: This is usually near the OBD-II port, but its exact location is vehicle specific. A manual might be helpful here.
* Connect the diagnostic connector appropriately: Many times the connector will need to be grounded and then the ignition switched on and off following a specific procedure. You will need to find the specific procedure for your year and model. There are many videos that might help.
* Observe the check engine light: The check engine light will flash a specific pattern, representing the Diagnostic Trouble Codes. You'll need a chart that details these flash codes. Finding a reliable chart for your specific model year can be difficult and may be inaccurate.
Recommendation: Using an OBD-II scanner is strongly recommended. It's far more accurate, easier to use, and provides more detailed information than trying to decipher flash codes. The cost of a basic scanner is a worthwhile investment for anyone who owns a car.
