GMC Sierra T1XX (2019-Present) check engine light keeps coming on why

Learn how to diagnose and fix the check engine light issue on GMC Sierra T1XX (2019-Present). Step-by-step guide with symptoms and solutions.

Solution

1. Preparation

• Gather tools and parts for the repair.
• Disconnect the negative battery terminal to ensure safety while working on electrical components.

2. Addressing Error Codes

• If codes indicate a specific issue (e.g., P0300 for misfire), follow up by replacing faulty components based on the codes retrieved.
  • For example, if misfire codes are present:
    • Replace faulty spark plugs and ignition coils.
    • Check and replace fuel injectors if necessary.

3. Inspecting and Replacing Components

• Gas Cap: If the gas cap is damaged or not sealing properly:

  • Remove the old gas cap.
  • Install a new gas cap that meets OEM specifications.

• Vacuum Leaks: If leaks are detected:

  • Locate and replace damaged hoses or gaskets.
  • Ensure all connections are tight and secure.

• Ignition System: For ignition issues:

  • Remove the ignition coils using a socket wrench.
  • Replace faulty coils and spark plugs with new units.
  • Torque the spark plugs to the manufacturer’s specifications (usually around 13 lb-ft).

4. Exhaust System Inspection

• If the catalytic converter is suspected:
  • Inspect for physical damage or blockage.
  • Replace the catalytic converter if necessary, ensuring proper fitment and alignment.

5. Fuel System Maintenance

• For fuel pressure issues:
  • Connect a fuel pressure gauge to the fuel rail.
  • If pressure is below specifications, replace the fuel pump or filter as needed.