why does my GMC Sierra T1XX (2019-Present) check engine light keep coming on

Learn how to diagnose and fix the check engine light issue in GMC Sierra T1XX (2019-Present). Step-by-step guide with symptoms, diagnostic steps, and repair instructions.

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to prevent electrical shorts.
• Ensure the vehicle is on a flat surface and securely supported if elevated.

2. Address Error Codes

• Retrieve the error codes from the OBD-II scanner.
• Interpret the codes to identify the specific issue (e.g., P0420 for catalytic converter efficiency).
• Research manufacturer specifications for the identified code.

3. Repair or Replace Affected Components

• If the issue is with the gas cap:
  • Remove the old gas cap and replace it with a new cap.
• If the issue is with the air filter:
  • Remove the air filter housing cover.
  • Replace the old filter with a new one, ensuring it fits securely.
• If the issue is related to the battery:
  • Clean the battery terminals and connections with a wire brush.
  • Replace the battery if it’s weak or faulty.
• If exhaust leaks are detected:
  • Inspect the exhaust manifold and pipes for cracks or holes.
  • Replace any damaged sections with new parts and ensure proper sealing.

4. Reconnect and Test

• Reconnect the battery and clear any fault codes using the OBD-II scanner.
• Start the engine and let it idle to observe for any abnormal behavior.
• Monitor the check engine light status for re-illumination.