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

Learn how to diagnose and fix a flashing check engine light on your GMC Sierra T1XX. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery cable to prevent electrical shorts.

2. Retrieve Diagnostic Codes

• Use an OBD-II scanner to connect to the vehicle's diagnostic port.
• Record any trouble codes that appear and reference them against a service manual for context.

3. Inspect Ignition Components

• Remove the engine cover if necessary.
• Check each spark plug for wear and replace if necessary (Torque to manufacturer specifications).
• Test ignition coils using a multimeter to ensure proper resistance (if faulty, replace).

4. Check Fuel System

• Connect a fuel pressure gauge to the fuel rail.
• Start the engine and check if the fuel pressure is within the specified range.
• Replace the fuel filter if pressure is low or if it has not been changed per the maintenance schedule.

5. Examine Exhaust System

• Look for any cracks or leaks in the exhaust manifold and pipes.
• Ensure that the catalytic converter is not clogged.
• If any defects are found, replace the affected components.

6. Inspect Air Intake and MAF Sensor

• Remove and inspect the air filter; replace if dirty.
• Clean the MAF sensor with a specific MAF cleaner, being careful not to touch the sensor element.
• Reinstall the air filter and MAF sensor.

7. Reconnect Battery

• Reconnect the negative battery cable securely.
• Start the engine and monitor for any check engine light activity.