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

Learn how to diagnose and fix P0401 EGR system issues in GMC Sierra T1XX. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before working on the EGR system.

2. Inspect and Clean EGR Valve

• Tools Required: Ratchet and socket set, cleaning solvent, soft brush.
• Remove the EGR valve from the engine by unscrewing the bolts holding it in place.
• Inspect the EGR valve for carbon deposits. If heavily clogged, use a cleaning solvent and a soft brush to clean the EGR valve thoroughly.
• Reinstall the EGR valve securely and torque to manufacturer specifications.

3. Clean EGR Passages

• Tools Required: Scraper tool, vacuum, cleaning solvent.
• Remove the EGR tube connected to the intake manifold.
• Use a scraper tool to gently remove carbon buildup from the EGR passages.
• Vacuum any debris and clean the area with a solvent.
• Reattach the EGR tube ensuring a secure connection.

4. Check EGR Valve Functionality

• Tools Required: Multimeter.
• Reconnect the EGR valve electrical connector.
• Use a multimeter to check the resistance of the EGR valve solenoid according to specifications (refer to service manual for exact values).
• If the valve is faulty, replace it with a new EGR valve.

5. Reassemble and Test

• Reconnect the negative battery terminal.
• Clear any diagnostic trouble codes using an OBD-II scanner.
• Start the engine and let it idle to check for any new codes or issues.