how to fix P0401 code on GMC Sierra T1XX (2019-Present)

Learn how to diagnose and fix P0401 code related to EGR system flow issues in GMC Sierra T1XX. Step-by-step guide with tools and procedures.

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to prevent electrical shorts.

2. Remove EGR Valve

1. Locate the EGR valve on the engine.
2. Remove the electrical connector from the EGR valve.
3. Unbolt the EGR valve using the appropriate socket.
4. Carefully remove the EGR valve from its mounting position.

3. Clean or Replace EGR Valve

• If cleaning:
  • Use an EGR valve cleaner and a soft brush to remove carbon deposits.
  • Rinse with clean water and allow it to dry completely.
• If replacing:
  • Install a new EGR valve, ensuring the gasket is properly aligned.

4. Clean EGR Passages

1. Locate the intake manifold and remove any components blocking access to the EGR passages.
2. Use a suitable cleaning solution and a brush to clean the EGR passages thoroughly.
3. Rinse with clean water and ensure no debris remains.

5. Reassemble Components

1. Reinstall the EGR valve, ensuring bolts are torqued to the manufacturer’s specifications (usually around 18-25 lb-ft).
2. Reconnect the electrical connector to the EGR valve.
3. Reinstall any components removed to access the EGR passages.

6. Reconnect Battery and Test

• Reconnect the battery terminals.
• Start the engine and allow it to reach operating temperature.